CN113009378B

CN113009378B - Battery micro short circuit detection method and device

Info

Publication number: CN113009378B
Application number: CN202110251227.3A
Authority: CN
Inventors: 高尚; 段崇伟; 张明轩
Original assignee: Jingwei Hengrun Tianjin Research And Development Co ltd
Current assignee: Jingwei Hengrun Tianjin Research And Development Co ltd
Priority date: 2021-03-08
Filing date: 2021-03-08
Publication date: 2022-03-29
Anticipated expiration: 2041-03-08
Also published as: CN113009378A

Abstract

The invention provides a method and a device for detecting micro short circuit of a battery, wherein the method comprises the following steps: respectively measuring the open-circuit voltage of the battery to be measured and the normal battery; after the battery to be tested and the normal battery are connected in parallel, measuring the current between the battery to be tested and the normal battery; calculating to obtain N judgment parameters according to the open-circuit voltage of the battery to be tested, the open-circuit voltage of the normal battery, the measured current and the corresponding relation between the state parameters of the battery to be tested and the normal battery which are calibrated in advance and the SOC, wherein N is more than or equal to 2; and when the at least two judgment parameters meet the preset conditions, determining that the battery to be tested is subjected to micro short circuit, otherwise, determining that the battery to be tested is not subjected to micro short circuit. The invention judges whether the micro short circuit occurs to the battery to be detected or not through the comprehensive analysis of at least two judgment parameters, and can detect whether the micro short circuit occurs or not under the condition that the balance is not performed between the single batteries.

Description

Battery micro short circuit detection method and device

Technical Field

The invention relates to the technical field of batteries, in particular to a battery micro short circuit detection method and device.

Background

The micro short circuit of the battery refers to a micro short circuit phenomenon between the battery cells of the battery pack or inside a single battery cell. Such a minute short circuit does not directly burn out the battery, but degrades the battery performance over a period of weeks or months, resulting in a certain cell or the entire battery pack being completely unusable. Therefore, it is necessary to detect a micro short circuit fault of the battery to ensure the safety of the battery. The existing detection scheme is to carry out micro short circuit detection on different battery monomers which are fully balanced; and when the battery cells are not equalized, micro short circuit detection cannot be performed.

Disclosure of Invention

In view of the above, the present invention provides a method and an apparatus for detecting a micro short circuit of a battery, which are intended to detect whether a micro short circuit occurs without performing equalization between battery cells.

In order to achieve the above object, the following solutions are proposed:

in a first aspect, a method for detecting a micro short circuit of a battery is provided, which includes:

respectively measuring the open-circuit voltage of the battery to be measured and the normal battery;

after the battery to be tested and the normal battery are connected in parallel, measuring the current between the battery to be tested and the normal battery;

calculating to obtain N judgment parameters according to the open-circuit voltage of the battery to be tested, the open-circuit voltage of the normal battery, the current and the corresponding relation between the state parameters of the battery to be tested and the normal battery which are calibrated in advance and the SOC, wherein N is more than or equal to 2;

and when at least two judgment parameters meet preset conditions, determining that the battery to be tested is subjected to micro short circuit, otherwise, determining that the battery to be tested is not subjected to micro short circuit.

Optionally, the N determination parameters include a first determination parameter, the state parameters of the to-be-detected battery and the normal battery include an open-circuit voltage, an ohmic internal resistance, a first polarization internal resistance, a second polarization internal resistance, a first polarization capacitance, and a second polarization capacitance, and the first determination parameter is obtained by calculation according to the open-circuit voltage of the to-be-detected battery, the open-circuit voltage of the normal battery, the current, and the corresponding relationship between the state parameters of the to-be-detected battery and the normal battery, which are calibrated in advance, and the SOC, and includes:

obtaining the SOC corresponding to the open-circuit voltage of the battery to be measured according to the corresponding relation between the open-circuit voltage and the SOC of the battery to be measured, which are calibrated in advance, and taking the SOC as the SOC of the battery to be measured at the initial moment;

obtaining the SOC corresponding to the measured open-circuit voltage of the normal battery according to the corresponding relation between the pre-calibrated open-circuit voltage of the normal battery and the SOC, and taking the SOC as the SOC of the normal battery at the initial moment;

the first polarization voltage and the second polarization voltage of the battery to be tested at the initial moment are both zero, and the first polarization voltage and the second polarization voltage of the normal battery at the initial moment are both zero;

obtaining a state parameter corresponding to the SOC of the battery to be tested at the kth moment according to a corresponding relation between the state parameter of the battery to be tested and the SOC calibrated in advance, and taking the state parameter as the state parameter of the battery to be tested at the kth moment;

obtaining a state parameter corresponding to the SOC of the normal battery at the kth moment according to a corresponding relation between the state parameter of the normal battery calibrated in advance and the SOC, and taking the state parameter as the state parameter of the normal battery at the kth moment;

calculating to obtain the current estimation value between the battery to be measured and the normal battery at the kth moment based on a current estimation formula, wherein the current estimation formula is as follows:

U_11,k+1＝U_11,kexp(-Δt/τ_11,k)+R_11,k[1-exp(-t/τ_11,k)]I_t,k

U_21,k+1＝U_21,kexp(-Δt/τ_21,k)+R_21,k[1-exp(-t/τ_21,k)]I_t,k

U_12,k+1＝U_12,kexp(-Δt/τ_12,k)+R_12,k[1-exp(-t/τ_12,k)]I_t,k

U_22,k+1＝U_22,kexp(-Δt/τ_22,k)+R_22,k[1-exp(-t/τ_22,k)]I_t,k

wherein, I_t,kOCV is the estimated value of current between the battery to be tested and the normal battery at the kth moment_1,k(SOC_1,k) Open circuit voltage, OCV, of a normal cell at time k_2,k(SOC_2,k) Is the open circuit voltage, U, of the battery to be tested at the kth moment_11,k+1Is the first polarization voltage, U, of the normal cell at time k +1_21,k+1Is the second polarization voltage, U, of the normal cell at time k +1_12,k+1Is the (k + 1) th timeFirst polarization voltage, U, of the battery to be tested_22,k+1Is the second polarization voltage, U, of the battery to be tested at the (k + 1) th moment_11,kIs the first polarization voltage, U, of the normal cell at the k-th time_21,kIs the second polarization voltage of the normal cell at the k-th time, U_12,kIs the first polarization voltage, U, of the cell to be measured at the kth moment_22,kIs the second polarization voltage of the battery to be tested at the kth moment, t is the time from the moment when the battery to be tested and the normal battery are connected in parallel to the kth moment, R_01,kOhmic internal resistance, R, of the normal cell at time k_02,kOhmic internal resistance, SOC, of the battery to be measured at the kth moment_1,kIs the SOC, SOC of the normal battery at the k-th time_2,kIs the SOC, SOC of the battery to be measured at the kth moment_1,k+1Is the SOC, SOC of the normal battery at the k +1 th time_2,k+1Is the SOC of the battery to be measured at the k +1 th moment, delta t is the time interval between the k +1 th moment and the k +1 th moment, eta₁Is the coulombic efficiency of a normal cell, η₂For the coulombic efficiency of the battery to be tested, C_bat1Is the capacity of a normal battery, C_bat2For the capacity of the battery to be tested, R_11,kIs the first polarization internal resistance, R, of the normal cell at the k-th time_21,kThe second polarization internal resistance, R, of the normal battery at the k-th time_12,kIs the first polarization internal resistance, R, of the battery to be measured at the kth moment_22,kFor the second internal polarization resistance, tau, of the cell to be measured at the kth moment_11,k＝R_11,kC_11,k、τ_21,k＝R_21,kC_21,k、τ_12,k＝R_12,kC_12,k、τ_22,k＝R_22,kC_22,k，τ_11,kIs the first time constant of the normal cell at time k, τ_21,kIs the second time constant of the normal cell at time k, τ_12,kIs the first time constant, tau, of the cell to be tested at the kth moment_22,kIs the second time constant, C, of the battery to be tested at the kth moment_11,kA first polarization capacitance, C, of a normal cell at the k-th moment_21,kA second polarization capacitance, C, of the normal cell at the k-th moment_12,kA first polarization capacitor, C, of the battery to be measured at the kth moment_22,kThe second polarization capacitor is the battery to be tested at the kth moment;

calculating to obtain a first judgment parameter based on a first judgment parameter formula, wherein the first judgment parameter formula is as follows:

wherein R is_judgeIs a first judgment parameter, U_m,kIs the terminal voltage measured value of the battery to be measured at the kth moment, I_m,kIs the current measurement value between the battery to be measured and the normal battery at the kth moment, I_t,kAnd n is the estimated value of the current between the battery to be measured and the normal battery at the kth moment.

Optionally, analyzing whether the first judgment parameter meets a preset condition includes:

and when the first judgment parameter is smaller than a preset first judgment parameter threshold value, determining that the first judgment parameter accords with a preset condition, otherwise, determining that the first judgment parameter does not accord with the preset condition.

Optionally, the N judgment parameters include a second judgment parameter, and the state parameters of the battery to be tested and the normal battery include an open-circuit voltage, an ohmic internal resistance, a first polarization internal resistance, a second polarization internal resistance, a first polarization capacitor and a second polarization capacitor; the calculating according to the open-circuit voltage of the battery to be tested, the open-circuit voltage of the normal battery, the current, and the corresponding relationship between the state parameters of the battery to be tested and the normal battery, which are calibrated in advance, and the SOC to obtain a second judgment parameter includes:

calculating to obtain the terminal voltages of the battery to be detected and the normal battery at the kth moment based on the terminal voltage estimation formulas of the battery to be detected and the normal battery respectively, wherein the terminal voltage estimation formulas of the battery to be detected and the normal battery are respectively as follows:

U_t1,k＝OCV_1,k(SOC_1,k)-I_m,kR_01,k-U_11,k-U_21,k

U_t2,k＝OCV_2,k(SOC_2,k)+I_m,kR_02,k-U_12,k-U_22,k

U_11,k+1＝U_11,kexp(-Δt/τ_11,k)+R_11,k[1-exp(-t/τ_11,k)]I_m,k

U_21,k+1＝U_21,kexp(-Δt/τ_21,k)+R_21,k[1-exp(-t/τ_21,k)]I_m,k

U_12,k+1＝U_12,kexp(-Δt/τ_12,k)+R_12,k[1-exp(-t/τ_12,k)]I_m,k

U_22,k+1＝U_22,kexp(-Δt/τ_22,k)+R_22,k[1-exp(-t/τ_22,k)]I_m,k

wherein, U_t1,kIs at k timeTerminal voltage estimation value of normal battery, U_t2,kIs the terminal voltage estimated value of the battery to be measured at the kth moment I_m,kThe measured value of the current between the battery to be tested and the normal battery at the kth moment, namely OCV_1,k(SOC_1,k) Open circuit voltage, OCV, of a normal cell at time k_2,k(SOC_2,k) Is the open circuit voltage, U, of the battery to be tested at the kth moment_11,k+1Is the first polarization voltage, U, of the normal cell at time k +1_21,k+1Is the second polarization voltage, U, of the normal cell at time k +1_12,k+1Is the first polarization voltage, U, of the battery to be tested at the (k + 1) th moment_22,k+1Is the second polarization voltage, U, of the battery to be tested at the (k + 1) th moment_11,kIs the first polarization voltage, U, of the normal cell at the k-th time_21,kIs the second polarization voltage of the normal cell at the k-th time, U_12,kIs the first polarization voltage, U, of the cell to be measured at the kth moment_22,kIs the second polarization voltage, R, of the cell to be tested at the kth moment_01,kOhmic internal resistance, R, of the normal cell at time k_02,kOhmic internal resistance, SOC, of the battery to be measured at the kth moment_1,kIs the SOC, SOC of the normal battery at the k-th time_2,kIs the SOC, SOC of the battery to be measured at the kth moment_1,k+1Is the SOC, SOC of the normal battery at the k +1 th time_2,k+1The SOC of the battery to be tested at the k +1 th moment, delta t is the time interval between the k th moment and the k +1 th moment, t is the time from the moment when the battery to be tested and the normal battery are connected in parallel to the k th moment, eta₁Is the coulombic efficiency of a normal cell, η₂For the coulombic efficiency of the battery to be tested, C_bat1Is the capacity of a normal battery, C_bat2For the capacity of the battery to be tested, R_11,kIs the first polarization internal resistance, R, of the normal cell at the k-th time_21,kThe second polarization internal resistance, R, of the normal battery at the k-th time_12,kIs the first polarization internal resistance, R, of the battery to be measured at the kth moment_22,kFor the second internal polarization resistance, tau, of the cell to be measured at the kth moment_11,k＝R_11,kC_11,k、τ_21,k＝R_21,kC_21,k、τ_12,k＝R_12,kC_12,k、τ_22,k＝R_22,kC_22,k，τ_11,kIs the first of the normal battery at the k-th momentTime constant, τ_21,kIs the second time constant of the normal cell at time k, τ_12,kIs the first time constant, tau, of the cell to be tested at the kth moment_22,kIs the second time constant, C, of the battery to be tested at the kth moment_11,kA first polarization capacitance, C, of a normal cell at the k-th moment_21,kA second polarization capacitance, C, of the normal cell at the k-th moment_12,kA first polarization capacitor, C, of the battery to be measured at the kth moment_22,kThe second polarization capacitor is the battery to be tested at the kth moment;

and calculating to obtain a second judgment parameter based on a second judgment parameter formula, wherein the second judgment parameter formula is as follows:

wherein, V_judgeIs the second judgment parameter, and n is the measurement ending time.

Optionally, analyzing whether the second judgment parameter meets a preset condition includes:

and when the second judgment parameter is larger than a preset second judgment parameter threshold value, determining that the second judgment parameter accords with a preset condition, otherwise, determining that the second judgment parameter does not accord with the preset condition.

Optionally, the N judgment parameters include a third judgment parameter, and the state parameters of the battery to be tested and the normal battery include open-circuit voltage and ohmic internal resistance; and calculating to obtain a third judgment parameter according to the open-circuit voltage of the battery to be tested, the open-circuit voltage of the normal battery, the current, and the corresponding relation between the state parameters of the battery to be tested and the normal battery, which are calibrated in advance, and the SOC, and the third judgment parameter comprises the following steps:

according to the corresponding relation between the ohmic internal resistance of the battery to be tested and the SOC calibrated in advance, obtaining the ohmic internal resistance corresponding to the SOC of the battery to be tested at the initial moment, and taking the ohmic internal resistance as the ohmic internal resistance of the battery to be tested at the initial moment;

according to the corresponding relation between the ohmic internal resistance of the normal battery and the SOC calibrated in advance, obtaining the ohmic internal resistance corresponding to the SOC of the normal battery at the initial moment, and taking the ohmic internal resistance as the ohmic internal resistance of the normal battery at the initial moment;

and calculating to obtain a third judgment parameter based on a third judgment parameter formula, wherein the third judgment parameter formula is as follows:

wherein R is_ISCIs a third judgment parameter, R_01,0Ohmic internal resistance, R, of a normal battery at an initial time_02,0Ohmic internal resistance, I, of the battery to be measured at the initial moment_1,0The OCV is the measured value of the current between the battery to be tested and the normal battery at the initial moment_1,0(SOC_1,0) Open circuit voltage, OCV, of a normal cell at an initial time_2,0(SOC_2,0) Open circuit voltage, SOC of battery to be measured at initial time_1,0Is the SOC, of a normal battery at an initial time_2,0The SOC of the battery to be measured at the initial moment is obtained.

Optionally, analyzing whether the third determination parameter meets a preset condition includes:

and when the third judgment parameter is smaller than a preset third judgment parameter threshold value, determining that the third judgment parameter accords with a preset condition, otherwise, determining that the third judgment parameter does not accord with the preset condition.

In a second aspect, a battery micro short detection device is provided, comprising:

the open-circuit voltage measuring unit is used for respectively measuring the open-circuit voltages of the battery to be measured and the normal battery;

the current measuring unit is used for measuring the current between the battery to be measured and the normal battery after the battery to be measured and the normal battery are connected in parallel;

the judgment parameter calculation unit is used for calculating N judgment parameters according to the open-circuit voltage of the battery to be detected, the open-circuit voltage of the normal battery, the current, the corresponding relation between the state parameters of the battery to be detected and the normal battery which are calibrated in advance and the SOC, wherein N is more than or equal to 2;

and the micro short circuit judging unit is used for determining that the battery to be tested has micro short circuit when at least two judging parameters meet the preset conditions, and otherwise, determining that the battery to be tested does not have micro short circuit.

Optionally, the N judgment parameters include a first judgment parameter, and the state parameters of the battery to be tested and the normal battery include an open-circuit voltage, an ohmic internal resistance, a first polarization internal resistance, a second polarization internal resistance, a first polarization capacitor and a second polarization capacitor; the judgment parameter calculation unit comprises a first judgment parameter calculation subunit, and the first judgment parameter calculation subunit is used for:

U_11,k+1＝U_11,kexp(-Δt/τ_11,k)+R_11,k[1-exp(-t/τ_11,k)]I_t,k

U_21,k+1＝U_21,kexp(-Δt/τ_21,k)+R_21,k[1-exp(-t/τ_21,k)]I_t,k

U_12,k+1＝U_12,kexp(-Δt/τ_12,k)+R_12,k[1-exp(-t/τ_12,k)]I_t,k

U_22,k+1＝U_22,kexp(-Δt/τ_22,k)+R_22,k[1-exp(-t/τ_22,k)]I_t,k

wherein, I_t,kOCV is the estimated value of current between the battery to be tested and the normal battery at the kth moment_1,k(SOC_1,k) Open circuit voltage, OCV, of a normal cell at time k_2,k(SOC_2,k) Is the open circuit voltage, U, of the battery to be tested at the kth moment_11,k+1Is the first polarization voltage, U, of the normal cell at time k +1_21,k+1Is the second polarization voltage, U, of the normal cell at time k +1_12,k+1Is the first polarization voltage, U, of the battery to be tested at the (k + 1) th moment_22,k+1Is the second polarization voltage, U, of the battery to be tested at the (k + 1) th moment_11,kIs the first polarization voltage, U, of the normal cell at the k-th time_21,kIs the second polarization voltage of the normal cell at the k-th time, U_12,kIs the first polarization voltage, U, of the cell to be measured at the kth moment_22,kIs the second polarization voltage of the battery to be tested at the kth moment, t is the voltage to be testedTime from the time when parallel connection of the battery and the normal battery is started to the k-th time, R_01,kOhmic internal resistance, R, of the normal cell at time k_02,kOhmic internal resistance, SOC, of the battery to be measured at the kth moment_1,kIs the SOC, SOC of the normal battery at the k-th time_2,kIs the SOC, SOC of the battery to be measured at the kth moment_1,k+1Is the SOC, SOC of the normal battery at the k +1 th time_2,k+1Is the SOC of the battery to be measured at the k +1 th moment, delta t is the time interval between the k +1 th moment and the k +1 th moment, eta₁Is the coulombic efficiency of a normal cell, η₂For the coulombic efficiency of the battery to be tested, C_bat1Is the capacity of a normal battery, C_bat2For the capacity of the battery to be tested, R_11,kIs the first polarization internal resistance, R, of the normal cell at the k-th time_21,kThe second polarization internal resistance, R, of the normal battery at the k-th time_12,kIs the first polarization internal resistance, R, of the battery to be measured at the kth moment_22,kFor the second internal polarization resistance, tau, of the cell to be measured at the kth moment_11,k＝R_11,kC_11,k、τ_21,k＝R_21,kC_21,k、τ_12,k＝R_12,kC_12,k、τ_22,k＝R_22,kC_22,k，τ_11,kIs the first time constant of the normal cell at time k, τ_21,kIs the second time constant of the normal cell at time k, τ_12,kIs the first time constant, tau, of the cell to be tested at the kth moment_22,kIs the second time constant, C, of the battery to be tested at the kth moment_11,kA first polarization capacitance, C, of a normal cell at the k-th moment_21,kA second polarization capacitance, C, of the normal cell at the k-th moment_12,kA first polarization capacitor, C, of the battery to be measured at the kth moment_22,kThe second polarization capacitor is the battery to be tested at the kth moment;

Optionally, the micro short circuit determining unit includes a first determining subunit, configured to:

Optionally, the N judgment parameters include a second judgment parameter, and the state parameters of the battery to be tested and the normal battery include an open-circuit voltage, an ohmic internal resistance, a first polarization internal resistance, a second polarization internal resistance, a first polarization capacitor and a second polarization capacitor; the judgment parameter calculation unit includes a second judgment parameter calculation subunit, and the second judgment parameter calculation subunit is configured to:

U_t1,k＝OCV_1,k(SOC_1,k)-I_m,kR_01,k-U_11,k-U_21,k

U_t2,k＝OCV_2,k(SOC_2,k)+I_m,kR_02,k-U_12,k-U_22,k

U_11,k+1＝U_11,kexp(-Δt/τ_11,k)+R_11,k[1-exp(-t/τ_11,k)]I_m,k

U_21,k+1＝U_21,kexp(-Δt/τ_21,k)+R_21,k[1-exp(-t/τ_21,k)]I_m,k

U_12,k+1＝U_12,kexp(-Δt/τ_12,k)+R_12,k[1-exp(-t/τ_12,k)]I_m,k

U_22,k+1＝U_22,kexp(-Δt/τ_22,k)+R_22,k[1-exp(-t/τ_22,k)]I_m,k

wherein, U_t1,kEstimate of terminal voltage of normal battery at the k-th time, U_t2,kIs the terminal voltage estimated value of the battery to be measured at the kth moment I_m,kThe measured value of the current between the battery to be tested and the normal battery at the kth moment, namely OCV_1,k(SOC_1,k) Open circuit voltage, OCV, of a normal cell at time k_2,k(SOC_2,k) Is the open circuit voltage, U, of the battery to be tested at the kth moment_11,k+1Is the first polarization voltage, U, of the normal cell at time k +1_21,k+1For normal cells at time k +1Second polarization voltage, U_12,k+1Is the first polarization voltage, U, of the battery to be tested at the (k + 1) th moment_22,k+1Is the second polarization voltage, U, of the battery to be tested at the (k + 1) th moment_11,kIs the first polarization voltage, U, of the normal cell at the k-th time_21,kIs the second polarization voltage of the normal cell at the k-th time, U_12,kIs the first polarization voltage, U, of the cell to be measured at the kth moment_22,kIs the second polarization voltage, R, of the cell to be tested at the kth moment_01,kOhmic internal resistance, R, of the normal cell at time k_02,kOhmic internal resistance, SOC, of the battery to be measured at the kth moment_1,kIs the SOC, SOC of the normal battery at the k-th time_2,kIs the SOC, SOC of the battery to be measured at the kth moment_1,k+1Is the SOC, SOC of the normal battery at the k +1 th time_2,k+1The SOC of the battery to be tested at the k +1 th moment, delta t is the time interval between the k th moment and the k +1 th moment, t is the time from the moment when the battery to be tested and the normal battery are connected in parallel to the k th moment, eta₁Is the coulombic efficiency of a normal cell, η₂For the coulombic efficiency of the battery to be tested, C_bat1Is the capacity of a normal battery, C_bat2For the capacity of the battery to be tested, R_11,kIs the first polarization internal resistance, R, of the normal cell at the k-th time_21,kThe second polarization internal resistance, R, of the normal battery at the k-th time_12,kIs the first polarization internal resistance, R, of the battery to be measured at the kth moment_22,kFor the second internal polarization resistance, tau, of the cell to be measured at the kth moment_11,k＝R_11,kC_11,k、τ_21,k＝R_21,kC_21,k、τ_12,k＝R_12,kC_12,k、τ_22,k＝R_22,kC_22,k，τ_11,kIs the first time constant of the normal cell at time k, τ_21,kIs the second time constant of the normal cell at time k, τ_12,kIs the first time constant, tau, of the cell to be tested at the kth moment_22,kIs the second time constant, C, of the battery to be tested at the kth moment_11,kA first polarization capacitance, C, of a normal cell at the k-th moment_21,kA second polarization capacitance, C, of the normal cell at the k-th moment_12,kA first polarization capacitor, C, of the battery to be measured at the kth moment_22,kIs the second pole of the battery to be tested at the kth momentConverting the capacitance;

Optionally, the micro short circuit determining unit includes a second determining subunit, configured to:

Optionally, the N judgment parameters include a third judgment parameter, and the state parameters of the battery to be tested and the normal battery include open-circuit voltage and ohmic internal resistance; the judgment parameter calculation unit includes a third judgment parameter calculation subunit, and the third judgment parameter calculation subunit is configured to:

Optionally, the micro short circuit determining unit includes a third determining subunit, configured to:

Compared with the prior art, the technical scheme of the invention has the following advantages:

the technical scheme provides a method and a device for detecting micro short circuit of a battery, wherein the method comprises the following steps: respectively measuring the open-circuit voltage of the battery to be measured and the normal battery; after the battery to be tested and the normal battery are connected in parallel, measuring the current between the battery to be tested and the normal battery; calculating to obtain N judgment parameters according to the open-circuit voltage of the battery to be tested, the open-circuit voltage of the normal battery, the measured current and the corresponding relation between the state parameters of the battery to be tested and the normal battery which are calibrated in advance and the SOC, wherein N is more than or equal to 2; and when the at least two judgment parameters meet the preset conditions, determining that the battery to be tested is subjected to micro short circuit, otherwise, determining that the battery to be tested is not subjected to micro short circuit. The invention judges whether the micro short circuit occurs to the battery to be detected or not through the comprehensive analysis of at least two judgment parameters, and can detect whether the micro short circuit occurs or not under the condition that the balance is not performed between the single batteries.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

Fig. 1 is a flowchart of a method for detecting a micro short circuit of a battery according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a detection circuit according to an embodiment of the present invention;

FIG. 3 is a diagram of a second order RC model of a battery;

FIG. 4 is an equivalent circuit diagram after the battery to be tested and the normal battery are connected in parallel;

FIG. 5 is an equivalent circuit diagram of a micro-short-circuited battery to be tested and a normal battery connected in parallel;

fig. 6 is a graph illustrating a current estimation value between a battery to be tested and a normal battery according to an embodiment of the present invention;

fig. 7 is a graph illustrating measured current values between a battery to be tested and a normal battery according to an embodiment of the present invention;

fig. 8 is a graph illustrating measured terminal voltage values of a battery according to an embodiment of the present invention;

fig. 9 is a graph illustrating terminal voltage estimated values of a battery to be tested and a normal battery according to an embodiment of the present invention;

fig. 10 is a schematic diagram of a logic structure of a battery micro short detection device according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1, the method for detecting a micro short circuit of a battery provided in this embodiment includes the following steps:

s11: and respectively measuring the open-circuit voltage of the battery to be measured and the normal battery.

A parameter detection circuit is shown in fig. 2, and comprises A, B, C and D four output interfaces which are respectively connected with the positive electrode and the negative electrode of a battery 1 and the positive electrode and the negative electrode of a battery 2. A and C are connected through a wire, and the conduction state is controlled by using a switch S. B and D are connected together through a lead. And the current collector is arranged on the wires connected with the B and the D and used for detecting the current flowing through the wires. The voltage sensor is used to measure the voltage before the a and B interfaces, and the voltage between the C and D interfaces. Wherein, the battery 1 is a normal battery, and the battery 2 is a battery to be tested.

In order to detect the micro short circuit of the battery, the battery to be detected and the normal battery are required to be sufficiently stood and then connected to the detection circuit in the manner shown in fig. 2. In general, it is considered that the battery is sufficiently left to stand after standing for 3 hours after the completion of charge and discharge of the battery. At this time, the battery does not have a polarization potential, and the terminal voltage of the battery is equal to the open circuit voltage of the battery, which can be obtained by measuring the terminal voltage of the battery. The application scene of the scheme can be after the vehicle leaves the factory or before the vehicle leaves the factory, and the scheme is suitable as long as whether the single battery is subjected to micro short circuit or not is required to be tested.

S12: and after the battery to be measured and the normal battery are connected in parallel, measuring the current between the battery to be measured and the normal battery.

S13: and calculating to obtain N judgment parameters according to the open-circuit voltage of the battery to be detected, the open-circuit voltage of the normal battery, the measured current and the corresponding relation between the state parameters of the battery to be detected and the normal battery and the SOC, wherein N is more than or equal to 2.

The present embodiment uses a second order RC model as an equivalent circuit model of the battery, as shown in fig. 3. The second-order RC model consists of open-circuit voltage OCV and ohmic internal resistance R₀And two resistor-capacitor parallel links (hereinafter referred to as RC parallel links). U shape_tRepresenting the terminal voltage of the battery. Electricity in RC parallel linkResistance R₁And R₂Referred to as internal resistance to polarization, R₁Referred to as the first polarization internal resistance, R₂Referred to as the second polarization internal resistance; capacitor C in RC parallel link₁And C₂Referred to as polarization capacitance, C₁Referred to as the first polarization voltage, C₂Referred to as the second polarization voltage. Ohmic internal resistance R₀Resistance R₁And R₂And a capacitor C₁And C₂Collectively referred to as the state parameters of the battery. The RC parallel link is used for describing concentration polarization and electrochemical polarization characteristics of the battery. Internal resistance of polarization R₁And R₂The voltages at both ends, i.e. the polarization voltages, are respectively denoted as U₁And U₂. Time constant τ₁＝R₁C₁，τ₂＝R₂C₂. By carrying out an HPPC experiment at the normal temperature of 25 ℃, state parameters such as OCV, ohmic internal resistance, polarization capacitance and the like of the battery at the normal temperature of 25 ℃ and in different charge states can be calibrated, namely the corresponding relation between each state parameter of the battery and the SOC is calibrated. The external characteristic equations of the second-order RC model are expressed by the following equations (1) to (3):

U₁＝I_tR₁·[1-exp(-t/τ₁)] (1)

U₂＝I_tR₂·[1-exp(-t/τ₂)] (2)

U_t＝OCV(SOC)-I_tR₀-U₁-U₂ (3)

wherein, I_tDenotes the current flowing through the battery, and t denotes the battery continuous current I_tOCV (SOC) represents the open circuit voltage OCV when the state of charge is SOC.

Discretization of the formula (1) and the formula (2) respectively can obtain the formula (4) and the formula (5):

U_1,k+1＝U_1,kexp(-Δt/τ_1,k)+R_1,k[1-exp(-t/τ_1,k)]I_t,k (4)

U_2,k+1＝U_2,kexp(-Δt/τ_2,k)+R_2,k[1-exp(-t/τ_2,k)]I_t,k (5)

wherein, U_1,kAnd U_2,kIs the polarization voltage of the cell at time k, i.e. U₁And U₂The value at the kth moment; u shape_1,k+1And U_2,k+1Is the polarization voltage of the cell at time k +1, i.e. U₁And U₂The value at the k +1 th moment; tau is_1,kAnd τ_2,kIs the time constant of the battery at time k, i.e. τ_1,kAnd τ_2,kThe value at the kth moment; r_1,kAnd R_2,kIs the internal polarization resistance of the cell at time k, i.e. R₁And R₂The value at the kth moment; i is_t,kIs the current through the battery at time k, i.e. I_tValue at time k +1, I_t,kAlso called the estimated value of the current between the battery to be tested and the normal battery at the kth moment, the embodiment specifies that the current flowing through the battery is positive when the battery is discharged; Δ t is the time interval between the kth time and the (k + 1) th time.

The discrete update equation of the state of charge SOC of the battery is shown in equation (6):

therein, SOC_kIs the state of charge, SOC, of the battery at time k_k+1The state of charge of the battery at the k +1 th moment; η is coulombic efficiency, typically approximately 1; c_batThe unit is the capacity of the battery, and is Ah.

Fig. 4 shows an equivalent circuit diagram of the battery to be tested and the normal battery connected in parallel. I is_tIndicating the current between the battery to be tested and the normal battery, OCV₁Represents the open circuit voltage, R, of a normal battery₀₁Indicates the ohmic internal resistance, R, of a normal battery₁₁Indicating a first internal polarization resistance, R, of a normal cell₂₁Indicating the second polarization internal resistance, C, of the normal cell₁₁First polarization capacitance, C, representing a normal battery₂₁Second polarization capacitance, OCV, representing a normal battery₂Representing the open-circuit voltage, R, of the battery under test₀₂Expressing the ohmic internal resistance, R, of the battery to be tested₁₂Indicating a first internal polarization resistance, R, of the battery to be tested₂₂Second pole representing battery to be testedTo reduce internal resistance, C₁₂Representing the first polarization capacitance, C, of the battery under test₂₂Representing the second polarization capacitance of the battery under test.

Since the normal battery and the battery to be tested are connected in parallel, equation (7) is satisfied, and equation (8) can be obtained by combining equations (3) and (7):

U_t1,k＝U_t2,k (7)

OCV_1,k(SOC_1,k)-I_t,kR_01,k-U_11,k-U_21,k＝OCV_2,k(SOC_2,k)+I_t,kR_02,k-U_12,k-U_22,k (8)

wherein, U_t1,kTerminal voltage of normal battery at time k, U_t2,kTerminal voltage of battery to be measured at time k, I_t,kOCV is the estimated value of current between the battery to be tested and the normal battery at the kth moment_1,k(SOC_1,k) Open circuit voltage, OCV, of a normal cell at time k_2,k(SOC_2,k) Is the open circuit voltage, U, of the battery to be tested at the kth moment_11,kIs the first polarization voltage, U, of the normal cell at the k-th time_21,kIs the second polarization voltage of the normal cell at the k-th time, U_12,kIs the first polarization voltage, U, of the cell to be measured at the kth moment_22,kIs the second polarization voltage, R, of the cell to be tested at the kth moment_01,kOhmic internal resistance, R, of the normal cell at time k_02,kOhmic internal resistance, SOC, of the battery to be measured at the kth moment_1,kIs the SOC, SOC of the normal battery at the k-th time_2,kThe SOC of the battery to be measured at the k moment is obtained.

By modification of formula (8), I can be obtained_t,kSee formula (9):

the corresponding relation between the state parameters of the battery to be tested and the normal battery and the SOC is obtained by pre-calibration, and comprises the corresponding relations between the open-circuit voltage, the ohmic internal resistance, the first polarization internal resistance, the second polarization internal resistance, the first polarization capacitance and the second polarization capacitance of the battery to be tested and the SOCAnd the corresponding relation between the open-circuit voltage, the ohmic internal resistance, the first polarization internal resistance, the second polarization internal resistance, the first polarization capacitance and the second polarization capacitance of the normal battery and the SOC. At a known SOC_1,k、SOC_2,k、U_11,k、U_21,k、U_12,kAnd U_22,kUnder the condition of waiting, obtaining the corresponding relation between the open-circuit voltage of the normal battery and the SOC according to the corresponding relation between the open-circuit voltage and the SOC which are calibrated in advance_1,kCorresponding OCV_1,k(SOC_1,k) (ii) a Obtaining the corresponding relation between the ohmic internal resistance of the normal battery and the SOC according to the corresponding relation between the ohmic internal resistance of the normal battery and the SOC which are calibrated in advance_1,kCorresponding R_01,k(ii) a Obtaining the SOC according to the corresponding relation between the open-circuit voltage and the SOC of the battery to be tested which is calibrated in advance_2,kCorresponding OCV_2,k(SOC_2,k) (ii) a Obtaining the corresponding relation between the ohmic internal resistance of the normal battery and the SOC according to the corresponding relation between the ohmic internal resistance of the normal battery and the SOC which are calibrated in advance_2,kCorresponding R_02,kAnd further can find I_t,k。

It is to be noted that the first polarization voltage U of the battery to be tested is initially present_12,0And a second polarization voltage U_22,0Are all zero, the first polarization voltage U of the normal battery at the initial moment_11,0And a second polarization voltage U_21,0Are all zero.

Reference formula (6), SOC_1,k+1And SOC_2,k+1These can be determined from equations (10) and (11):

wherein, C_bat1Is the capacity of a normal battery, C_bat2To the capacity of the cell to be tested, eta₁Is the coulombic efficiency of a normal cell, η₂For the coulombic efficiency, SOC, of the battery to be measured_1,k+1Is the SOC, SOC of the normal battery at the k +1 th time_2,k+1Is the SOC and SOC of the battery to be measured at the k +1 th moment_1,kIs a normal battery at the k timeSOC, SOC_2,kThe SOC of the battery to be measured at the k moment is obtained.

The SOC is obtained by the equations (10) and (11)_1,k+1And SOC_2,k+1And then, according to the corresponding relation between the state parameters of the normal battery and the battery to be tested and the SOC obtained by calibration, obtaining the open-circuit voltage, the ohmic internal resistance, the first polarization internal resistance, the second polarization internal resistance, the first polarization capacitor and the second polarization capacitor of the normal battery and the battery to be tested at the moment of k + 1. And further obtaining a first time constant and a second time constant of the normal battery and the battery to be tested at the moment k + 1. With reference to equations (4) and (5), a first polarization voltage and a second polarization voltage of the normal battery and the battery to be tested at the time k +1 can be obtained from equations (12), (13), (14) and (15), respectively:

U_11,k+1＝U_11,kexp(-Δt/τ_11,k)+R_11,k[1-exp(-t/τ_11,k)]I_t,k (12)

U_21,k+1＝U_21,kexp(-Δt/τ_21,k)+R_21,k[1-exp(-t/τ_21,k)]I_t,k (13)

U_12,k+1＝U_12,kexp(-Δt/τ_12,k)+R_12,k[1-exp(-t/τ_12,k)]I_t,k (14)

U_22,k+1＝U_22,kexp(-Δt/τ_22,k)+R_22,k[1-exp(-t/τ_22,k)]I_t,k (15)

wherein, U_11,k+1Is the first polarization voltage, U, of the normal cell at time k +1_21,k+1Is the second polarization voltage, U, of the normal cell at time k +1_12,k+1Is the first polarization voltage, U, of the battery to be tested at the (k + 1) th moment_22,k+1The second polarization voltage of the battery to be tested at the k +1 th moment, t is the time from the moment when the battery to be tested and the normal battery are connected in parallel to the k th moment, delta t is the time interval between the k th moment and the k +1 th moment, R_11,kIs the first polarization internal resistance, R, of the normal cell at the k-th time_21,kThe second polarization internal resistance, R, of the normal battery at the k-th time_12,kIs the first polarization internal resistance, R, of the battery to be measured at the kth moment_22,kIs the k-th timeSecond internal polarization resistance, tau, of the battery to be tested_11,k＝R_11,kC_11,k、τ_21,k＝R_21,kC_21,k、τ_12,k＝R_12,kC_12,k、τ_22,k＝R_22,kC_22,k，τ_11,kIs the first time constant of the normal cell at time k, τ_21,kIs the second time constant of the normal cell at time k, τ_12,kIs the first time constant, tau, of the cell to be tested at the kth moment_22,kIs the second time constant, C, of the battery to be tested at the kth moment_11,kA first polarization capacitance, C, of a normal cell at the k-th moment_21,kA second polarization capacitance, C, of the normal cell at the k-th moment_12,kA first polarization capacitor, C, of the battery to be measured at the kth moment_22,kThe second polarization capacitance of the battery to be tested at the kth moment.

By recombination of formula (9) to obtain I_t,k+1. Therefore, under the condition that the SOC of the normal battery and the SOC of the battery to be measured at the initial moment are known, the current estimation value between the battery to be measured and the normal battery at any moment can be obtained continuously and iteratively by using the formulas (9) to (15).

Judging the parameters to be parameters representing the micro short circuit degree of the battery to be tested; if a certain judgment parameter meets the preset condition, the possibility of micro short circuit of the battery to be tested is high. In some embodiments, the determination parameter may include a first determination parameter R_judgeSecond judgment parameter V_judgeAnd a third judgment parameter R_ISC. First judgment parameter R_judgeThe physical meaning of (1) is an approximate estimation value of the micro short circuit resistance of the battery to be tested; first judgment parameter R_judgeThe smaller the resistance, the smaller the micro short circuit resistance and the more serious the micro short circuit; first judgment parameter R_judgeThe larger the resistance, the larger the micro short circuit resistance and the lighter the micro short circuit; first judgment parameter R_judgeAnd when the voltage is infinite, the battery to be tested does not have micro short circuit. Second judgment parameter V_judgeThe physical meaning of (1) is the difference degree between the terminal voltage estimated value of the battery to be tested and the terminal voltage estimated value of the battery (normal battery) which is connected in parallel and has no micro short circuit; second judgment parameter V_judgeThe smaller the size, the smaller the micro-short circuitThe lighter; second judgment parameter V_judgeThe larger the size, the more serious the micro short circuit. Third judgment parameter R_ISCThe physical meaning of (1) is a transient estimation value of the micro short circuit resistance of the battery to be tested; the transient state refers to the initial moment when the battery to be tested is connected with the normal battery in parallel; third judgment parameter R_ISCThe smaller the resistance, the smaller the micro short circuit resistance and the more serious the micro short circuit; third judgment parameter R_ISCThe larger the resistance, the larger the micro short circuit resistance and the lighter the micro short circuit; third judgment parameter R_ISCAnd when the voltage is infinite, the battery to be tested does not have micro short circuit. In practical application, the preset conditions corresponding to the judgment parameters are determined according to experience and calibration, and whether the calculated judgment parameters meet the preset conditions or not can be determined. Obviously, for a judgment parameter with a larger value and a lighter micro short circuit, the judgment parameter is smaller than a preset condition determined according to experience and calibration, and the judgment parameter is determined to meet the preset condition. On the contrary, for the judgment parameter with larger value and more serious micro short circuit, when the judgment parameter is larger than the preset condition determined according to experience and calibration, the judgment parameter is determined to accord with the preset condition. First judgment parameter R_judgeThe calculation process of (2) is as follows:

(21) and obtaining the SOC corresponding to the measured open-circuit voltage of the battery to be measured according to the corresponding relation between the pre-calibrated open-circuit voltage and the SOC of the battery to be measured, and taking the SOC as the SOC of the battery to be measured at the initial moment.

After the battery to be measured is sufficiently static, measuring the initial terminal voltage U of the battery to be measured_t2,0；U_t2,0It is the open-circuit voltage OCV of the battery to be measured obtained by the measurement of the invention_2,0I.e. the open-circuit voltage OCV of the battery to be tested at the initial moment_2，0(SOC_2，0). SOC for SOC of battery to be measured at initial time_2,0And (4) showing.

(22) And obtaining the SOC corresponding to the measured open-circuit voltage of the normal battery according to the corresponding relation between the pre-calibrated open-circuit voltage and the SOC of the normal battery, and taking the SOC as the SOC of the normal battery at the initial moment.

After the normal battery is sufficiently stationary, the initial value of the normal battery is measuredTerminal voltage U_t1,0；U_t1,0It means that the open circuit voltage OCV of the normal battery obtained by the measurement in the present invention_1,0I.e. the open circuit voltage OCV of the normal battery at the initial moment_1,0(SOC_1,0). SOC for SOC of normal battery at initial time_1,0And (4) showing.

(23) First polarization voltage U of battery to be tested at initial moment_12,0And a second polarization voltage U_22,0Are all zero, the first polarization voltage U of the normal battery at the initial moment_11,0And a second polarization voltage U_21,0Are all zero.

(24) And obtaining a state parameter corresponding to the SOC of the battery to be tested at the kth moment according to the corresponding relation between the state parameter of the battery to be tested and the SOC calibrated in advance, and taking the state parameter as the state parameter of the battery to be tested at the kth moment.

The state parameters in step (24) include open circuit voltage, ohmic internal resistance, first polarization internal resistance, second polarization internal resistance, first polarization capacitance, and second polarization capacitance. After the SOC of the battery to be tested at the initial time is obtained, each state parameter of the battery to be tested at the initial time can be obtained according to the corresponding relationship between each state parameter of the battery to be tested and the SOC which is calibrated in advance; after obtaining the SOC and each state parameter of the battery to be tested at the initial moment, the SOC of the battery to be tested at other moments can be obtained according to the expressions (9) to (15), and then each state parameter of the battery to be tested at other moments is obtained according to the corresponding relation between each state parameter of the battery to be tested and the SOC which is calibrated in advance.

(25) And obtaining a state parameter corresponding to the SOC of the normal battery at the kth moment according to the corresponding relation between the state parameter of the normal battery and the SOC calibrated in advance, and taking the state parameter as the state parameter of the normal battery at the kth moment.

The state parameters in step (25) also include open circuit voltage, ohmic internal resistance, first polarization internal resistance, second polarization internal resistance, first polarization capacitance, and second polarization capacitance. Similarly, after the SOC of the normal battery at the initial time is obtained, each state parameter of the normal battery at the initial time can be obtained according to the corresponding relationship between each state parameter of the normal battery and the SOC calibrated in advance; after obtaining the SOC and each state parameter of the battery to be measured at the initial moment, the SOC of the battery to be measured at other moments can be obtained according to the expressions (9) to (15), and then each state parameter of the normal battery at other moments is obtained according to the corresponding relation between each state parameter of the normal battery and the SOC which is calibrated in advance.

(26) Based on a current estimation formula, calculating to obtain an estimated current value I between the battery to be tested and the normal battery at the kth moment_t,k。

The current estimation formula includes equations (9) to (15).

(27) And calculating to obtain a first judgment parameter based on the first judgment parameter formula.

The first judgment parameter formula is as follows:

Second judgment parameter V_judgeThe calculation process of (2) is as follows:

(31) and obtaining the SOC corresponding to the measured open-circuit voltage of the battery to be measured according to the corresponding relation between the pre-calibrated open-circuit voltage and the SOC of the battery to be measured, and taking the SOC as the SOC of the battery to be measured at the initial moment.

(32) And obtaining the SOC corresponding to the measured open-circuit voltage of the normal battery according to the corresponding relation between the pre-calibrated open-circuit voltage and the SOC of the normal battery, and taking the SOC as the SOC of the normal battery at the initial moment.

(33) The first polarization voltage and the second polarization voltage of the battery to be tested at the initial moment are both zero, and the first polarization voltage and the second polarization voltage of the normal battery at the initial moment are both zero.

(34) And obtaining a state parameter corresponding to the SOC of the battery to be tested at the kth moment according to the corresponding relation between the state parameter of the battery to be tested and the SOC calibrated in advance, and taking the state parameter as the state parameter of the battery to be tested at the kth moment.

The state parameters in step (34) include open circuit voltage, ohmic internal resistance, first polarization internal resistance, second polarization internal resistance, first polarization capacitance, and second polarization capacitance. After the SOC of the battery to be tested at the initial time is obtained, each state parameter of the battery to be tested at the initial time can be obtained according to the corresponding relationship between each state parameter of the battery to be tested and the SOC which is calibrated in advance; after obtaining the SOC and each state parameter of the battery to be tested at the initial moment, the SOC of the battery to be tested at other moments can be obtained according to the formulas (19) and (20), and then each state parameter of the battery to be tested at other moments is obtained according to the corresponding relation between each state parameter of the battery to be tested and the SOC which is calibrated in advance.

(35) And obtaining a state parameter corresponding to the SOC of the normal battery at the kth moment according to the corresponding relation between the state parameter of the normal battery and the SOC calibrated in advance, and taking the state parameter as the state parameter of the normal battery at the kth moment.

The state parameters in step (35) also include open circuit voltage, ohmic internal resistance, first polarization internal resistance, second polarization internal resistance, first polarization capacitance, and second polarization capacitance. Similarly, after the SOC of the normal battery at the initial time is obtained, each state parameter of the normal battery at the initial time can be obtained according to the corresponding relationship between each state parameter of the normal battery and the SOC calibrated in advance; after obtaining the SOC and each state parameter of the normal battery at the initial moment, the SOC of the normal battery at other moments can be obtained according to the expressions (19) and (20), and then each state parameter of the normal battery at other moments is obtained according to the corresponding relation between each state parameter of the battery to be tested and the SOC which is calibrated in advance.

(36) And calculating to obtain the terminal voltages of the battery to be detected and the normal battery at the kth moment based on the terminal voltage estimation formulas of the battery to be detected and the normal battery respectively.

The terminal voltage estimation formulas of the battery to be tested and the normal battery comprise:

U_t1,k＝OCV_1,k(SOC_1,k)-I_m,kR_01,k-U_11,k-U_21,k (17)

U_t2,k＝OCV_2,k(SOC_2,k)+I_m,kR_02,k-U_12,k-U_22,k (18)

U_11,k+1＝U_11,kexp(-Δt/τ_11,k)+R_11,k[1-exp(-t/τ_11,k)]I_m,k (21)

U_21,k+1＝U_21,kexp(-Δt/τ_21,k)+R_21,k[1-exp(-t/τ_21,k)]I_m,k (22)

U_12,k+1＝U_12,kexp(-Δt/τ_12,k)+R_12,k[1-exp(-t/τ_12,k)]I_m,k (23)

U_22,k+1＝U_22,kexp(-Δt/τ_22,k)+R_22,k[1-exp(-t/τ_22,k)]I_m,k (24)

wherein, U_11,k+1Is the first polarization voltage, U, of the normal cell at time k +1_21,k+1Is the second polarization voltage, U, of the normal cell at time k +1_12,k+1Is the first polarization voltage, U, of the battery to be tested at the (k + 1) th moment_22,k+1Is the second polarization voltage, U, of the battery to be tested at the (k + 1) th moment_11,kIs the first polarization voltage, U, of the normal cell at the k-th time_21,kIs the second polarization voltage of the normal cell at the k-th time, U_12,kIs the first polarization voltage, U, of the cell to be measured at the kth moment_22,kIs the second polarization voltage, U, of the cell to be tested at the kth moment_t1,kEstimate of terminal voltage of normal battery at the k-th time, U_t2,kIs the terminal voltage estimated value of the battery to be measured at the kth moment I_m,kFor measuring the current between the battery to be measured and the normal battery at the kth momentValue, OCV_1,k(SOC_1,k) Open circuit voltage, OCV, of a normal cell at time k_2,k(SOC_2,k) Is the open circuit voltage, R, of the cell to be tested at the kth moment_01,kOhmic internal resistance, R, of the normal cell at time k_02,kOhmic internal resistance, SOC, of the battery to be measured at the kth moment_1,kIs the SOC, SOC of the normal battery at the k-th time_2,kIs the SOC, SOC of the battery to be measured at the kth moment_1,k+1Is the SOC, SOC of the normal battery at the k +1 th time_2,k+1The SOC of the battery to be tested at the k +1 th moment, delta t is the time interval between the k th moment and the k +1 th moment, t is the time from the moment when the battery to be tested and the normal battery are connected in parallel to the k th moment, R_11,kIs the first polarization internal resistance, R, of the normal cell at the k-th time_21,kThe second polarization internal resistance, R, of the normal battery at the k-th time_12,kIs the first polarization internal resistance, R, of the battery to be measured at the kth moment_22,kFor the second internal polarization resistance, tau, of the cell to be measured at the kth moment_11,k＝R_11,kC_11,k、τ_21,k＝R_21,kC_21,k、τ_12,k＝R_12,kC_12,k、τ_22,k＝R_22,kC_22,k，τ_11,kIs the first time constant of the normal cell at time k, τ_21,kIs the second time constant of the normal cell at time k, τ_12,kIs the first time constant, tau, of the cell to be tested at the kth moment_22,kIs the second time constant, C, of the battery to be tested at the kth moment_11,kA first polarization capacitance, C, of a normal cell at the k-th moment_21,kA second polarization capacitance, C, of the normal cell at the k-th moment_12,kA first polarization capacitor, C, of the battery to be measured at the kth moment_22,kThe second polarization capacitance of the battery to be tested at the kth moment.

(37) And calculating to obtain a second judgment parameter based on the second judgment parameter formula.

The second judgment parameter formula is as follows:

Third judgment parameter R_{ISC_judge}The calculation process of (2) is as follows:

(41) and obtaining the SOC corresponding to the measured open-circuit voltage of the battery to be measured according to the corresponding relation between the pre-calibrated open-circuit voltage and the SOC of the battery to be measured, and taking the SOC as the SOC of the battery to be measured at the initial moment.

(42) And obtaining the SOC corresponding to the measured open-circuit voltage of the normal battery according to the corresponding relation between the pre-calibrated open-circuit voltage and the SOC of the normal battery, and taking the SOC as the SOC of the normal battery at the initial moment.

(43) And obtaining the ohmic internal resistance corresponding to the initial time SOC of the battery to be tested according to the corresponding relation between the ohmic internal resistance of the battery to be tested and the SOC calibrated in advance, and taking the ohmic internal resistance as the ohmic internal resistance of the battery to be tested at the initial time.

(44) And obtaining the ohmic internal resistance corresponding to the initial time SOC of the normal battery according to the corresponding relation between the ohmic internal resistance of the normal battery and the SOC calibrated in advance, and taking the ohmic internal resistance as the ohmic internal resistance of the normal battery at the initial time.

(45) And calculating to obtain a third judgment parameter based on the third judgment parameter formula.

The third judgment parameter formula is:

See FIG. 5, I₁Is the current that flows through the normal battery,I₂is the current flowing through the battery under test. According to kirchhoff's law, the circuit satisfies equation (27) and equation (28) at the initial time:

(I_1,0+I_2,0)R_ISC＝OCV_1,0(SOC_1,0)-I_1,0R_01,0-U_11,0-U_21,0 (27)

(I_1,0+I_2,0)R_ISC＝OCV_2,0(SOC_2,0)-I_2,0R_02,0-U_12,0-U_22,0 (28)

first polarization voltage U of normal battery at initial moment_11,0And a second polarization voltage U_21,0Are all zero, the first polarization voltage U of the battery to be measured at the initial moment_12,0And a second polarization voltage U_22,0Are also both zero, and therefore, according to formulas (27) and (28)

Formulae (29) and (30) can be obtained:

(I_1,0+I_2,0)R_ISC＝OCV_1,0(SOC_1,0)-I_1,0R_01,0 (29)

(I_1,0+I_2,0)R_ISC＝OCV_2,0(SOC_2,0)-I_2,0R_02,0 (30)

obtaining formula (31) according to formulae (29) and (30):

OCV_1,0(SOC_1,0)-I_1,0R_01,0＝OCV_2,0(SOC_2,0)-I_2,0R_02,0 (31)

modification of equation (31) yields equation (32):

I_2,0R_02,0＝OCV_2,0(SOC_2,0)-OCV_1,0(SOC_1,0)+I_1,0R_01,0 (32)

on both sides of the equation of the formula (32), R is multiplied by_ISCTo give formula (33):

I_2,0R_02,0R_ISC＝OCV_2,0(SOC_2,0)R_ISC-OCV_1,0(SOC_1,0)R_ISC+I_1,0R_01,0R_ISC (33)

on both sides of the equation of the formula (29), R is multiplied_02,0To give formula (34):

I_1,0R_02,0R_ISC+I_2,0R_02,0R_ISC＝OCV_1,0(SOC_1,0)R_02,0-I_1,0R_01,0R_02,0 (34)

combining formulae (33) and (34) gives formula (35):

I_1,0R_02,0R_ISC+OCV_2,0(SOC_2,0)R_ISC-OCV_1,0(SOC_1,0)R_ISC+I_1,0R_01,0R_ISC＝OCV_1,0(SOC_1,0)R_02,0-I_1,0R_01,0R_02,0

(35)

the expression (26) can be obtained by converting the expression (35).

S14: and when the at least two judgment parameters meet the preset conditions, determining that the battery to be tested is subjected to micro short circuit, otherwise, determining that the battery to be tested is not subjected to micro short circuit.

And closing a switch S in the detection circuit, namely, after the battery to be detected and the normal battery are connected in parallel, acquiring the battery end voltage and current of the battery to be detected in real time. If the current I collected at the moment k_m,kGreater than the current I estimated by the model_t,kAnd indicating that the battery to be tested has micro short circuit. The equivalent circuit diagram of the battery to be tested with micro short circuit is shown in fig. 5. In this case, the current I in the circuit_m,kThe battery not only contains balance current, but also comprises micro short-circuit current, and the magnitude of the micro short-circuit current is the terminal voltage U of the battery to be tested_m,kAnd a micro short-circuit resistor R_ISCQuotient of is U_m,k/R_ISC. Due to micro short circuit resistance R_ISCIs unknown, so the actual equalization current value cannot be obtained. Can use the I obtained by model-based calculation under the condition of no micro short circuit_t,kAs an estimate of the equalizing current, this estimate andthere will be some difference in the actual values. First judgment parameter R defined using equation (16)_judgeAs an index for judging whether or not a micro short circuit occurs. When the first judgment parameter R_judgeWhen the voltage is smaller, the micro short circuit of the battery to be tested is shown, and the first judgment parameter R_judgeThe smaller the micro-short resistance, the more severe the micro-short. When the first judgment parameter R_judgeAnd when the voltage is infinite, the battery to be tested does not have micro short circuit. When the first judgment parameter R_judgeWhen the size is larger, the battery to be tested may not have micro short circuit, and the judgment parameter R is caused by the error of the model and the error of sampling_judgeNot infinite. In some embodiments, the first determination parameter threshold Δ R is used as the determination criterion, R_judgeIf < delta R, the risk of micro short circuit is considered to be large, and R is determined_judgeThe preset conditions are met; r_judgeIf not less than delta R, the micro short circuit risk is considered to be small, and R is determined_judgeThe preset condition is not met. The value of Δ R may be 5000 Ω.

If the battery has no micro short circuit and the model precision and the sampling precision are high enough, the estimated terminal voltage U_t1,kAnd U_t2,kShould be the same. If the estimated terminal voltage U_t1,kAnd U_t2,kIf there is a large difference, it indicates that the battery to be tested has a micro short circuit. As shown in formula (25), definition V_judgeAnother indicator for determining whether or not a micro short circuit occurs in the battery may be used as the second determination parameter. In some embodiments, the second determination parameter threshold Δ V is used as the determination criterion when V is greater than V_judgeWhen the voltage is more than delta V, the micro short circuit risk is considered to be high, and V is determined_judgeThe preset conditions are met; when V is_judgeWhen the voltage is less than or equal to delta V, the micro short circuit risk is considered to be small, and V is determined_judgeThe preset condition is not met. The value of Δ V may be specifically 0.003V.

When the battery to be tested does not have micro short circuit, the third judgment parameter R_ISCIs infinite. In some embodiments, the third determination parameter threshold Δ R is set_ISCAs a judgment criterion, when R_ISC＜ΔR_ISCWhen the wind is in the short circuit, the wind is considered to be slightly short-circuitedAt greater risk, determine R_ISCThe preset conditions are met; when R is_ISC≥ΔR_ISCThen, the risk of micro short circuit is considered to be smaller, and R is determined_ISCThe preset condition is not met. Δ R_ISCSpecifically, the value may be 1000 Ω.

And when the micro short circuit is actually judged, the three judgment parameters are integrated for judgment. When only one judgment condition is used for judgment, the accuracy of micro short circuit identification may be influenced by misjudgment due to factors such as detection errors, model errors or signal interference, and the like, so that the three judgment conditions are integrated for judgment. And when any two judgment parameters meet the preset conditions, the battery to be tested is considered to have micro short circuit.

An example of the detection method proposed by the present invention is given below. Example conditions were set as: the battery types of the battery to be tested and the normal battery are both 20 Ah. The cell to be tested had a 1000 ohm micro-short resistance.

The terminal voltages of the normal battery and the battery to be tested were detected to be 4.096V and 4.090V, respectively, thereby obtaining the SOC of the normal battery and the SOC of the battery to be tested to be 90% and 89.5%, respectively, at the initial time. From equations (9) to (15), the estimated current value between the battery to be measured and the normal battery can be estimated, as shown in fig. 6. The measurement results show that the current measurement value between the battery to be measured and the normal battery, and the terminal voltage measurement value of the battery to be measured are shown in fig. 7 and fig. 8, respectively. n is 600 and Δ t is 1 s. Calculating to obtain a first judgment parameter R_judge1761 ohms and less than the first judgment parameter threshold Δ R of 5000 ohms, that is, the first judgment parameter meets the preset condition. From the formulas (17) to (24), the terminal voltage estimated values U of the normal battery and the battery to be measured can be obtained_t1,kAnd U_t2,kAs shown in fig. 9. The value of n is 600, the value of delta t is 1s, and a second judgment parameter V is obtained through calculation_judge0.00388V, the second determination parameter threshold Δ V is greater than 0.003V, i.e., the second determination parameter meets the predetermined condition. R is calculated from the formula (26)_ISC268 ohms and less than the third judgment parameter threshold value Delta R_ISC1000 ohms, that is, the third determination parameter also meets the preset condition. Since all three judgment parameters meet the preset conditions,therefore, it is determined that the micro short circuit of the battery under test has occurred.

While, for purposes of simplicity of explanation, the foregoing method embodiments have been described as a series of acts or combination of acts, it will be appreciated by those skilled in the art that the present invention is not limited by the illustrated ordering of acts, as some steps may occur in other orders or concurrently with other steps in accordance with the invention.

The following are embodiments of the apparatus of the present invention that may be used to perform embodiments of the method of the present invention. For details which are not disclosed in the embodiments of the apparatus of the present invention, reference is made to the embodiments of the method of the present invention.

Referring to fig. 10, the device for detecting a micro short circuit of a battery provided in this embodiment includes: an open circuit voltage measuring unit 101, a current measuring unit 102, a judgment parameter calculating unit 103, and a micro short circuit judging unit 104.

And an open-circuit voltage measuring unit 101 for measuring open-circuit voltages of the battery to be measured and the normal battery, respectively.

And the current measuring unit 102 is used for measuring the current between the battery to be measured and the normal battery after the battery to be measured and the normal battery are connected in parallel.

And the judgment parameter calculation unit 103 is used for calculating N judgment parameters according to the open-circuit voltage of the battery to be tested, the open-circuit voltage of the normal battery, the measured current, and the corresponding relationship between the state parameters of the battery to be tested and the normal battery, which are calibrated in advance, and the SOC, wherein N is more than or equal to 2.

And the micro short circuit judging unit 104 is configured to determine that the battery to be tested has a micro short circuit when at least two of the judging parameters meet a preset condition, and otherwise, determine that the battery to be tested has no micro short circuit.

In some implementations, the N determination parameters include a first determination parameter, and the state parameters of the battery to be tested and the normal battery include an open-circuit voltage, an ohmic internal resistance, a first polarization internal resistance, a second polarization internal resistance, a first polarization capacitor, and a second polarization capacitor; the judgment parameter calculation unit 103 includes a first judgment parameter calculation subunit. The first judgment parameter calculation subunit is used for:

U_11,k+1＝U_11,kexp(-Δt/τ_11,k)+R_11,k[1-exp(-t/τ_11,k)]I_t,k

U_21,k+1＝U_21,kexp(-Δt/τ_21,k)+R_21,k[1-exp(-t/τ_21,k)]I_t,k

U_12,k+1＝U_12,kexp(-Δt/τ_12,k)+R_12,k[1-exp(-t/τ_12,k)]I_t,k

U_22,k+1＝U_22,kexp(-Δt/τ_22,k)+R_22,k[1-exp(-t/τ_22,k)]I_t,k

wherein, I_t,kOCV is the estimated value of current between the battery to be tested and the normal battery at the kth moment_1,k(SOC_1,k) Open circuit voltage, OCV, of a normal cell at time k_2,k(SOC_2,k) Is the open circuit voltage, U, of the battery to be tested at the kth moment_11,k+1Is the first polarization voltage, U, of the normal cell at time k +1_21,k+1Is the second polarization voltage, U, of the normal cell at time k +1_12,k+1Is the first polarization voltage, U, of the battery to be tested at the (k + 1) th moment_22,k+1Is the second polarization voltage, U, of the battery to be tested at the (k + 1) th moment_11,kIs the first polarization voltage, U, of the normal cell at the k-th time_21,kIs the second polarization voltage of the normal cell at the k-th time, U_12,kIs the first polarization voltage, U, of the cell to be measured at the kth moment_22,kIs the second polarization voltage of the battery to be tested at the kth moment, t is the time from the moment when the battery to be tested and the normal battery are connected in parallel to the kth moment, R_01,kOhmic internal resistance, R, of the normal cell at time k_02,kOhmic internal resistance, SOC, of the battery to be measured at the kth moment_1,kIs the SOC, SOC of the normal battery at the k-th time_2,kIs the SOC, SOC of the battery to be measured at the kth moment_1,k+1Is the SOC, SOC of the normal battery at the k +1 th time_2,k+1Is the SOC of the battery to be measured at the k +1 th moment, delta t is the time interval between the k +1 th moment and the k +1 th moment, eta₁Is the coulombic efficiency of a normal cell, η₂For the coulombic efficiency of the battery to be tested, C_bat1Is the capacity of a normal battery, C_bat2For the capacity of the battery to be tested, R_11,kIs the first polarization internal resistance, R, of the normal cell at the k-th time_21,kThe second polarization internal resistance, R, of the normal battery at the k-th time_12,kIs the first polarization internal resistance, R, of the battery to be measured at the kth moment_22,kFor the second internal polarization resistance, tau, of the cell to be measured at the kth moment_11,k＝R_11,kC_11,k、τ_21,k＝R_21,kC_21,k、τ_12,k＝R_12,kC_12,k、τ_22,k＝R_22,kC_22,k，τ_11,kIs the first time constant of the normal cell at time k, τ_21,kIs the second time constant of the normal cell at time k, τ_12,kIs the first time constant, tau, of the cell to be tested at the kth moment_22,kIs the second time constant, C, of the battery to be tested at the kth moment_11,kA first polarization capacitance, C, of a normal cell at the k-th moment_21,kA second polarization capacitance, C, of the normal cell at the k-th moment_12,kA first polarization capacitor, C, of the battery to be measured at the kth moment_22,kThe second polarization capacitor is the battery to be tested at the kth moment;

In some embodiments, the micro short circuit determining unit 104 includes a first determining subunit configured to: and when the first judgment parameter is smaller than a preset first judgment parameter threshold value, determining that the first judgment parameter accords with a preset condition, otherwise, determining that the first judgment parameter does not accord with the preset condition.

In some embodiments, the N determination parameters include a second determination parameter, and the state parameters of the battery to be tested and the normal battery include an open-circuit voltage, an ohmic internal resistance, a first polarization internal resistance, a second polarization internal resistance, a first polarization capacitor, and a second polarization capacitor; the judgment parameter calculation unit 103 includes a second judgment parameter calculation subunit. The second judgment parameter calculation subunit is configured to:

obtaining a state parameter corresponding to the SOC of the battery to be tested at the kth moment according to the corresponding relation between the state parameter of the battery to be tested and the SOC calibrated in advance, and taking the state parameter as the state parameter of the battery to be tested at the kth moment;

obtaining a state parameter corresponding to the SOC of the normal battery at the kth moment according to the corresponding relation between the state parameter of the normal battery calibrated in advance and the SOC, and taking the state parameter as the state parameter of the normal battery at the kth moment;

U_t1,k＝OCV_1,k(SOC_1,k)-I_m,kR_01,k-U_11,k-U_21,k

U_t2,k＝OCV_2,k(SOC_2,k)+I_m,kR_02,k-U_12,k-U_22,k

U_11,k+1＝U_11,kexp(-Δt/τ_11,k)+R_11,k[1-exp(-t/τ_11,k)]I_m,k

U_21,k+1＝U_21,kexp(-Δt/τ_21,k)+R_21,k[1-exp(-t/τ_21,k)]I_m,k

U_12,k+1＝U_12,kexp(-Δt/τ_12,k)+R_12,k[1-exp(-t/τ_12,k)]I_m,k

U_22,k+1＝U_22,kexp(-Δt/τ_22,k)+R_22,k[1-exp(-t/τ_22,k)]I_m,k

wherein, U_t1,kEstimate of terminal voltage of normal battery at the k-th time, U_t2,kIs the terminal voltage estimated value of the battery to be measured at the kth moment I_m,kThe measured value of the current between the battery to be tested and the normal battery at the kth moment, namely OCV_1,k(SOC_1,k) Open circuit voltage, OCV, of a normal cell at time k_2,k(SOC_2,k) Is the open circuit voltage, U, of the battery to be tested at the kth moment_11,k+1Is the first polarization voltage, U, of the normal cell at time k +1_21,k+1Is the second polarization voltage, U, of the normal cell at time k +1_12,k+1Is the first polarization voltage, U, of the battery to be tested at the (k + 1) th moment_22,k+1Is the second polarization voltage, U, of the battery to be tested at the (k + 1) th moment_11,kIs the first polarization voltage, U, of the normal cell at the k-th time_21,kIs the second polarization voltage of the normal cell at the k-th time, U_12,kIs the first polarization voltage, U, of the cell to be measured at the kth moment_22,kIs the second polarization voltage, R, of the cell to be tested at the kth moment_01,kOhmic internal resistance, R, of the normal cell at time k_02,kOhmic internal resistance, SOC, of the battery to be measured at the kth moment_1,kIs the SOC, SOC of the normal battery at the k-th time_2,kIs the SOC, SOC of the battery to be measured at the kth moment_1,k+1Is the SOC, SOC of the normal battery at the k +1 th time_2,k+1The SOC of the battery to be tested at the k +1 th moment, delta t is the time interval between the k th moment and the k +1 th moment, t is the time from the moment when the battery to be tested and the normal battery are connected in parallel to the k th moment, eta₁Coulombic efficiency as a normal cell，η₂For the coulombic efficiency of the battery to be tested, C_bat1Is the capacity of a normal battery, C_bat2For the capacity of the battery to be tested, R_11,kIs the first polarization internal resistance, R, of the normal cell at the k-th time_21,kThe second polarization internal resistance, R, of the normal battery at the k-th time_12,kIs the first polarization internal resistance, R, of the battery to be measured at the kth moment_22,kFor the second internal polarization resistance, tau, of the cell to be measured at the kth moment_11,k＝R_11,kC_11,k、τ_21,k＝R_21,kC_21,k、τ_12,k＝R_12,kC_12,k、τ_22,k＝R_22,kC_22,kτ_11,kIs the first time constant of the normal cell at time k, τ_21,kIs the second time constant of the normal cell at time k, τ_12,kIs the first time constant, tau, of the cell to be tested at the kth moment_22,kIs the second time constant, C, of the battery to be tested at the kth moment_11,kA first polarization capacitance, C, of a normal cell at the k-th moment_21,kA second polarization capacitance, C, of the normal cell at the k-th moment_12,kA first polarization capacitor, C, of the battery to be measured at the kth moment_22,kThe second polarization capacitor is the battery to be tested at the kth moment;

In some embodiments, the micro short circuit determining unit 104 includes a second determining subunit configured to: and when the second judgment parameter is larger than a preset second judgment parameter threshold value, determining that the second judgment parameter accords with a preset condition, otherwise, determining that the second judgment parameter does not accord with the preset condition.

In some embodiments, the N determination parameters include a third determination parameter, and the state parameters of the battery to be tested and the normal battery include an open-circuit voltage and an ohmic internal resistance; the judgment parameter calculation unit 103 includes a third judgment parameter calculation subunit. The third judgment parameter calculation subunit is used for:

In some embodiments, the micro short circuit determining unit 104 includes a third determining subunit configured to: and when the third judgment parameter is smaller than a preset third judgment parameter threshold value, determining that the third judgment parameter accords with a preset condition, otherwise, determining that the third judgment parameter does not accord with the preset condition.

The above-described embodiments of the apparatus are merely illustrative, and the units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.

In this document, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

The embodiments in the present description are mainly described as different from other embodiments, the same and similar parts in the embodiments may be referred to each other, and the features described in the embodiments in the present description may be replaced with each other or combined with each other.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A battery micro short circuit detection method is characterized by comprising the following steps:

calculating to obtain N judgment parameters according to the open-circuit voltage of the battery to be tested, the open-circuit voltage of the normal battery, the current and the corresponding relation between the state parameters of the battery to be tested and the normal battery which are calibrated in advance and the SOC, wherein N is more than or equal to 2; the N judgment parameters comprise a first judgment parameter, a second judgment parameter and a third judgment parameter;

when at least two judgment parameters meet preset conditions, determining that the battery to be tested is subjected to micro short circuit, otherwise, determining that the battery to be tested is not subjected to micro short circuit;

the first judgment parameter formula is shown as the following formula,

wherein R is_judgeIs a first judgment parameter, U_m,kIs the terminal voltage measured value of the battery to be measured at the kth moment, I_m,kIs the current measurement value between the battery to be measured and the normal battery at the kth moment, I_t,kThe current estimation value between the battery to be measured and the normal battery at the kth moment is obtained, and n is the measurement ending moment;

the second decision parameter formula is shown as follows,

wherein, V_judgeIs a second determination parameter, n is a measurement end time, U_t1,kEstimate of terminal voltage of normal battery at the k-th time, U_t2,kThe terminal voltage estimated value of the battery to be measured at the kth moment is delta t, and the time interval between the kth moment and the (k + 1) th moment is delta t;

the third judgment parameter formula is shown as the following formula,

2. The method for detecting the micro short circuit of the battery according to claim 1, wherein the state parameters of the battery to be tested and the normal battery include an open-circuit voltage, an ohmic internal resistance, a first polarized internal resistance, a second polarized internal resistance, a first polarized capacitance and a second polarized capacitance, and the calculating of the first judgment parameter according to the open-circuit voltage of the battery to be tested, the open-circuit voltage of the normal battery, the current, and the corresponding relationship between the state parameters of the battery to be tested and the normal battery, which are calibrated in advance, and the SOC comprises:

obtaining the SOC corresponding to the measured open-circuit voltage of the normal battery according to the corresponding relation between the pre-calibrated open-circuit voltage of the normal battery and the SOC, and taking the SOC as the SOC of the normal battery at the initial moment; the first polarization voltage and the second polarization voltage of the battery to be tested at the initial moment are both zero, and the first polarization voltage and the second polarization voltage of the normal battery at the initial moment are both zero;

U_11,k+1＝U_11,kexp(-Δt/τ_11,k)+R_11,k[1-exp(-t/τ_11,k)]I_t,k

U_21,k+1＝U_21,kexp(-Δt/τ_21,k)+R_21,k[1-exp(-t/τ_21,k)]I_t,k

U_12,k+1＝U_12,kexp(-Δt/τ_12,k)+R_12,k[1-exp(-t/τ_12,k)]I_t,k

U_22,k+1＝U_22,kexp(-Δt/τ_22,k)+R_22,k[1-exp(-t/τ_22,k)]I_t,k

and calculating to obtain a first judgment parameter based on the first judgment parameter formula.

3. The method for detecting micro short circuit of battery as claimed in claim 2, wherein analyzing whether the first determination parameter meets a predetermined condition comprises:

4. The battery micro short circuit detection method according to claim 1, wherein the state parameters of the battery to be tested and the normal battery include open circuit voltage, ohmic internal resistance, first polarization internal resistance, second polarization internal resistance, first polarization capacitance and second polarization capacitance; the calculating according to the open-circuit voltage of the battery to be tested, the open-circuit voltage of the normal battery, the current, and the corresponding relationship between the state parameters of the battery to be tested and the normal battery, which are calibrated in advance, and the SOC to obtain a second judgment parameter includes:

U_t1,k＝OCV_1,k(SOC_1,k)-I_m,kR_01,k-U_11,k-U_21,k

U_t2,k＝OCV_2,k(SOC_2,k)+I_m,kR_02,k-U_12,k-U_22,k

U_11,k+1＝U_11,kexp(-Δt/τ_11,k)+R_11,k[1-exp(-t/τ_11,k)]I_m,k

U_21,k+1＝U_21,kexp(-Δt/τ_21,k)+R_21,k[1-exp(-t/τ_21,k)]I_m,k

U_12,k+1＝U_12,kexp(-Δt/τ_12,k)+R_12,k[1-exp(-t/τ_12,k)]I_m,k

U_22,k+1＝U_22,kexp(-Δt/τ_22,k)+R_22,k[1-exp(-t/τ_22,k)]I_m,k

wherein, U_t1,kEstimate of terminal voltage of normal battery at the k-th time, U_t2,kIs the terminal voltage estimated value of the battery to be measured at the kth moment I_m,kThe measured value of the current between the battery to be tested and the normal battery at the kth moment, namely OCV_1,k(SOC_1,k) Open circuit voltage, OCV, of a normal cell at time k_2,k(SOC_2,k) Is the open circuit voltage, U, of the battery to be tested at the kth moment_11,k+1Is the first polarization voltage, U, of the normal cell at time k +1_21,k+1Is the second polarization voltage, U, of the normal cell at time k +1_12,k+1Is the first polarization voltage, U, of the battery to be tested at the (k + 1) th moment_22,k+1Is the second polarization voltage, U, of the battery to be tested at the (k + 1) th moment_11,kIs the first polarization voltage, U, of the normal cell at the k-th time_21,kIs the second polarization voltage of the normal cell at the k-th time, U_12,kIs the first polarization voltage, U, of the cell to be measured at the kth moment_22,kIs the second polarization voltage, R, of the cell to be tested at the kth moment_01,kOhmic internal resistance, R, of the normal cell at time k_02,kOhmic internal resistance, SOC, of the battery to be measured at the kth moment_1,kIs the SOC, SOC of the normal battery at the k-th time_2,kIs the SOC, SOC of the battery to be measured at the kth moment_1,k+1Is the SOC, SOC of the normal battery at the k +1 th time_2,k+1The SOC of the battery to be tested at the k +1 th moment, delta t is the time interval between the k th moment and the k +1 th moment, t is the time from the moment when the battery to be tested and the normal battery are connected in parallel to the k th moment, eta₁Is the coulombic efficiency of a normal cell, η₂For the coulombic efficiency of the battery to be tested, C_bat1Is the capacity of a normal battery, C_bat2For the capacity of the battery to be tested, R_11,kIs the first polarization internal resistance, R, of the normal cell at the k-th time_21,kThe second polarization internal resistance, R, of the normal battery at the k-th time_12,kIs the first polarization internal resistance, R, of the battery to be measured at the kth moment_22,kFor the second internal polarization resistance, tau, of the cell to be measured at the kth moment_11,k＝R_11,kC_11,k、τ_21,k＝R_21,kC_21,k、τ_12,k＝R_12,kC_12,k、τ_22,k＝R_22,kC_22,k，τ_11,kIs the first time constant of the normal cell at time k, τ_21,kIs the second time constant of the normal cell at time k, τ_12,kIs the first time constant, tau, of the cell to be tested at the kth moment_22,kIs the second time constant, C, of the battery to be tested at the kth moment_11,kA first polarization capacitance, C, of a normal cell at the k-th moment_21,kA second polarization capacitance, C, of the normal cell at the k-th moment_12,kA first polarization capacitor, C, of the battery to be measured at the kth moment_22,kThe second polarization capacitor is the battery to be tested at the kth moment;

and calculating to obtain a second judgment parameter based on the second judgment parameter formula.

5. The method for detecting micro short circuit of battery as claimed in claim 4, wherein analyzing whether the second determination parameter meets a predetermined condition comprises:

6. The battery micro short circuit detection method according to claim 1, wherein the state parameters of the battery to be tested and the normal battery include open circuit voltage and ohmic internal resistance; and calculating to obtain a third judgment parameter according to the open-circuit voltage of the battery to be tested, the open-circuit voltage of the normal battery, the current, and the corresponding relation between the state parameters of the battery to be tested and the normal battery, which are calibrated in advance, and the SOC, and the third judgment parameter comprises the following steps:

and calculating to obtain a third judgment parameter based on the third judgment parameter formula.

7. The method for detecting micro short circuit of battery as claimed in claim 6, wherein analyzing whether the third determination parameter meets the predetermined condition comprises:

8. A battery micro short detection device, comprising:

the judgment parameter calculation unit is used for calculating N judgment parameters according to the open-circuit voltage of the battery to be detected, the open-circuit voltage of the normal battery, the current, the corresponding relation between the state parameters of the battery to be detected and the normal battery which are calibrated in advance and the SOC, wherein N is more than or equal to 2; the N judgment parameters comprise a first judgment parameter, a second judgment parameter and a third judgment parameter;

the micro short circuit judging unit is used for determining that the battery to be tested has micro short circuit when at least two judging parameters meet the preset conditions, and otherwise, determining that the battery to be tested does not have micro short circuit;

the first judgment parameter formula is shown as the following formula,

the second decision parameter formula is shown as follows,

the third judgment parameter formula is shown as the following formula,

9. The battery micro short detection device according to claim 8, wherein the state parameters of the battery to be tested and the normal battery include open circuit voltage, ohmic internal resistance, first polarization internal resistance, second polarization internal resistance, first polarization capacitance and second polarization capacitance; the judgment parameter calculation unit comprises a first judgment parameter calculation subunit, and the first judgment parameter calculation subunit is used for:

U_11,k+1＝U_11,kexp(-Δt/τ_11,k)+R_11,k[1-exp(-t/τ_11,k)]I_t,k

U_21,k+1＝U_21,kexp(-Δt/τ_21,k)+R_21,k[1-exp(-t/τ_21,k)]I_t,k

U_12,k+1＝U_12,kexp(-Δt/τ_12,k)+R_12,k[1-exp(-t/τ_12,k)]I_t,k

U_22,k+1＝U_22,kexp(-Δt/τ_22,k)+R_22,k[1-exp(-t/τ_22,k)]I_t,k

10. The battery micro short circuit detection device according to claim 8, wherein the N judgment parameters include a second judgment parameter, and the state parameters of the battery to be tested and the normal battery include an open circuit voltage, an ohmic internal resistance, a first polarization internal resistance, a second polarization internal resistance, a first polarization capacitance and a second polarization capacitance; the judgment parameter calculation unit includes a second judgment parameter calculation subunit, and the second judgment parameter calculation subunit is configured to:

U_t1,k＝OCV_1,k(SOC_1,k)-I_m,kR_01,k-U_11,k-U_21,k

U_t2,k＝OCV_2,k(SOC_2,k)+I_m,kR_02,k-U_12,k-U_22,k

U_11,k+1＝U_11,kexp(-Δt/τ_11,k)+R_11,k[1-exp(-t/τ_11,k)]I_m,k

U_21,k+1＝U_21,kexp(-Δt/τ_21,k)+R_21,k[1-exp(-t/τ_21,k)]I_m,k

U_12,k+1＝U_12,kexp(-Δt/τ_12,k)+R_12,k[1-exp(-t/τ_12,k)]I_m,k

U_22,k+1＝U_22,kexp(-Δt/τ_22,k)+R_22,k[1-exp(-t/τ_22,k)]I_m,k

wherein, U_t1,kEstimate of terminal voltage of normal battery at the k-th time, U_t2,kIs the terminal voltage estimated value of the battery to be measured at the kth moment I_m,kThe measured value of the current between the battery to be tested and the normal battery at the kth moment, namely OCV_1,k(SOC_1,k) Open circuit voltage, OCV, of a normal cell at time k_2,k(SOC_2,k) Is the open circuit voltage, U, of the battery to be tested at the kth moment_11,k+1Is the first polarization voltage, U, of the normal cell at time k +1_21,k+1Is the second polarization voltage, U, of the normal cell at time k +1_12,k+1Is the first polarization voltage, U, of the battery to be tested at the (k + 1) th moment_22,k+1Is the second polarization voltage, U, of the battery to be tested at the (k + 1) th moment_11,kIs the first polarization voltage, U, of the normal cell at the k-th time_21,kIs the second polarization voltage of the normal cell at the k-th time, U_12,kIs the first polarization voltage, U, of the cell to be measured at the kth moment_22,kIs the second polarization voltage, R, of the cell to be tested at the kth moment_01,kOhmic internal resistance, R, of the normal cell at time k_02,kOhmic internal resistance, SOC, of the battery to be measured at the kth moment_1,kIs the SOC, SOC of the normal battery at the k-th time_2,kIs the SOC, SOC of the battery to be measured at the kth moment_1,k+1Is the SOC, SOC of the normal battery at the k +1 th time_2,k+1The SOC of the battery to be tested at the k +1 th moment, delta t is the time interval between the k th moment and the k +1 th moment, t is the time from the moment when the battery to be tested and the normal battery are connected in parallel to the k th moment, eta₁Is the coulombic efficiency of a normal cell, η₂For the coulombic efficiency of the battery to be tested, C_bat1Is the capacity of a normal battery, C_bat2For the capacity of the battery to be tested, R_11,kIs the first polarization internal resistance, R, of the normal cell at the k-th time_21,kThe second polarization internal resistance, R, of the normal battery at the k-th time_12,kIs the first polarization internal resistance, R, of the battery to be measured at the kth moment_22,kIn the second polarization of the cell to be tested at the kth momentResistance, tau_11,k＝R_11,kC_11,k、τ_21,k＝R_21,kC_21,k、τ_12,k＝R_12,kC_12,k、τ_22,k＝R_22,kC_22,k，τ_11,kIs the first time constant of the normal cell at time k, τ_21,kIs the second time constant of the normal cell at time k, τ_12,kIs the first time constant, tau, of the cell to be tested at the kth moment_22,kIs the second time constant, C, of the battery to be tested at the kth moment_11,kA first polarization capacitance, C, of a normal cell at the k-th moment_21,kA second polarization capacitance, C, of the normal cell at the k-th moment_12,kA first polarization capacitor, C, of the battery to be measured at the kth moment_22,kThe second polarization capacitor is the battery to be tested at the kth moment;