CN109435768B

CN109435768B - Battery equalization method, system, vehicle, storage medium and electronic equipment

Info

Publication number: CN109435768B
Application number: CN201710773468.8A
Authority: CN
Inventors: 罗红斌; 王超; 沈晓峰; 曾求勇; 刘苑红; 张祥
Original assignee: BYD Co Ltd
Current assignee: BYD Co Ltd
Priority date: 2017-08-31
Filing date: 2017-08-31
Publication date: 2024-01-09
Anticipated expiration: 2037-08-31
Also published as: CN109435768A

Abstract

The present disclosure relates to a battery equalization method, system, vehicle, storage medium and electronic device, the method comprising: obtaining the voltage change rate of each single battery in the battery pack; determining a reference voltage change rate required by balance judgment according to the voltage change rate of each single battery in the battery pack; and determining the single battery to be balanced according to the voltage change rate of at least one single battery and the reference voltage change rate. By adopting the method, the single battery to be balanced is determined according to the voltage change rate of at least one single battery in the battery pack. The single battery to be balanced is not fixed any more according to the SOC value or the load voltage value, the voltage change rate of the single battery is used as the battery information according to which the single battery to be balanced is determined, the battery information according to which the single battery to be balanced is determined is enriched, and a diversified method for determining the single battery to be balanced is provided.

Description

Battery equalization method, system, vehicle, storage medium and electronic equipment

Technical Field

The disclosure relates to the technical field of control, and in particular relates to a battery balancing method, a system, a vehicle, a storage medium and electronic equipment.

Background

High capacity batteries that provide a source of motive energy for electric vehicles are often referred to as power cells. The power battery for the vehicle is generally formed by connecting a plurality of single batteries in series to form a module. As the battery is used, the difference between the individual battery cells gradually expands, the uniformity between the battery cells is poor, and the capacity of the battery pack is limited due to the short plate effect of the battery, so that the capacity of the battery pack cannot be fully exerted, and the overall capacity of the battery pack is reduced. On the other hand, the difference between the single batteries gradually expands, which causes overcharge of some single batteries, overdischarge of some single batteries, influences the service life of the batteries, damages the batteries, and may generate a large amount of heat to cause combustion or explosion of the batteries.

Therefore, the power battery of the electric automobile is effectively and uniformly managed, the consistency of each battery in the battery pack is improved, the capacity loss of the battery is reduced, the service life of the battery and the driving range of the electric automobile are prolonged, and the method has very important significance.

At present, the power battery pack is subjected to balancing management, and firstly, single batteries needing to be balanced are determined from the power battery pack, so that battery information of all the single batteries in the power battery pack needs to be collected in real time, and then, the single batteries needing to be balanced are determined according to the battery information (for example, an SOC value and a load voltage value), and then, the single batteries needing to be balanced are balanced. Therefore, the battery information on which the single battery to be balanced is determined is single.

Disclosure of Invention

An object of the present disclosure is to provide a battery equalization method, system, vehicle, storage medium and electronic device to optimize a battery equalization process.

To achieve the above object, a first aspect of the present disclosure provides a battery equalization method, the method comprising:

obtaining the voltage change rate of each single battery in the battery pack;

determining a reference voltage change rate required by balance judgment according to the voltage change rate of each single battery in the battery pack;

and determining the single battery to be balanced according to the voltage change rate of at least one single battery and the reference voltage change rate.

Optionally, the determining the unit cell to be balanced according to the voltage change rate of the at least one unit cell and the reference voltage change rate includes:

determining a voltage change rate difference between the voltage change rate of the at least one unit cell and the reference voltage change rate;

acquiring an equilibrium starting threshold value;

and determining the single battery with the voltage change rate difference value larger than or equal to the balance starting threshold value in the at least one single battery as the single battery needing to be balanced.

Optionally, the determining the reference voltage change rate required for the equalization judgment according to the voltage change rate of each single battery in the battery pack includes:

Determining the minimum value of the voltage change rates of all the single batteries in the battery pack as the reference voltage change rate;

the determining a voltage change rate difference between the voltage change rate of the at least one unit cell and the reference voltage change rate includes:

determining a voltage change rate difference between a voltage change rate of the following unit cells and the reference voltage change rate:

the single battery with the largest voltage change rate in the battery pack; or (b)

And the battery pack comprises other single batteries except the single battery with the minimum voltage change rate.

Optionally, after determining that the cell having the voltage change rate difference value greater than or equal to the equalization-on threshold in the at least one cell is a cell requiring equalization, the method further includes:

when the battery pack is in the charging process, controlling the single batteries of which the voltage change rate difference value is larger than or equal to the balance starting threshold value in the at least one single battery to discharge;

and when the battery pack is in the discharging process, controlling the single batteries of which the voltage change rate difference value is larger than or equal to the balance starting threshold value in the at least one single battery to charge.

determining the maximum value of the voltage change rates of all the single batteries in the battery pack as the reference voltage change rate;

the single battery with the minimum voltage change rate in the battery pack; or (b)

And the battery pack comprises other single batteries except the single battery with the maximum voltage change rate.

when the battery pack is in the charging process, controlling the single batteries of which the voltage change rate difference value is larger than or equal to the balance starting threshold value in the at least one single battery to be charged;

and when the battery pack is in the discharging process, controlling the single batteries of which the voltage change rate difference value is larger than or equal to the balance starting threshold value in the at least one single battery to discharge.

determining an average value of the voltage change rates of the individual battery cells in the battery pack as the reference voltage change rate;

and determining a voltage change rate difference value between the voltage change rate of each single battery in the battery pack and the reference voltage change rate.

when the battery pack is in the charging process, controlling the single batteries of which the voltage change rate is smaller than the average value in the single batteries to be balanced to be charged, and controlling the single batteries of which the voltage change rate is larger than the average value in the single batteries to be balanced to be discharged;

when the battery pack is in the discharging process, controlling the single batteries of which the voltage change rate is smaller than the average value in the single batteries to be balanced to discharge, and controlling the single batteries of which the voltage change rate is larger than the average value in the single batteries to be balanced to charge.

Optionally, after determining the cell to be equalized according to the voltage change rate of the at least one cell and the reference voltage change rate, the method further includes:

determining a target equalization duration of the single battery to be equalized according to the voltage change rate of the single battery to be equalized and the reference voltage change rate;

and controlling the balance of the single batteries to be balanced according to the target balance duration of the single batteries to be balanced.

Optionally, the acquiring the voltage change rate of each unit cell in the battery pack includes:

charging or discharging unit electric quantity to each single battery in the battery pack;

and for each single battery in the battery pack, determining the voltage variation of the single battery as the variation generated by the change of the load voltage value of the single battery along with the change of the electric quantity by the unit electric quantity.

charging or discharging each single battery in the battery pack for unit time;

and for each single battery in the battery pack, determining the voltage variation of the single battery as the variation of the voltage value of the single battery along with the unit time of charging/discharging the single battery.

A second aspect of the present disclosure provides a battery equalization system, comprising: the balance module, the acquisition module and the control module,

the acquisition module is used for acquiring the voltage change rate of each single battery in the battery pack;

the control module is used for determining the reference voltage change rate required by equalization judgment according to the voltage change rate of each single battery in the battery pack, and determining the single battery to be equalized according to the voltage change rate of at least one single battery and the reference voltage change rate;

the balancing module is used for balancing the single batteries to be balanced.

Optionally, the control module is configured to:

acquiring an equilibrium starting threshold value;

Optionally, the control module is configured to:

determining the minimum value of the voltage change rates of all the single batteries in the battery pack as the reference voltage change rate; or alternatively

Determining the maximum value of the voltage change rates of all the single batteries in the battery pack as the reference voltage change rate; or alternatively

And determining an average value of the voltage change rates of the individual single cells in the battery pack as the reference voltage change rate.

Optionally, the control module is configured to:

the equalization module is used for:

and balancing the single batteries to be balanced according to the target balancing duration of the single batteries to be balanced.

Optionally, the control module is configured to:

charging or discharging each single battery in the battery pack for unit time;

Optionally, the control module is connected with the acquisition module and the equalization module corresponding to the same single battery through a channel, and the control module is used for controlling the control module to be connected with the corresponding sampling module when the single battery connected with the control module is determined not to be equalized; or,

the control module is also used for controlling the control module to be connected with the corresponding sampling module at the first time and connected with the corresponding equalization module at the second time when the single batteries connected with the control module are determined to be required to be equalized.

Optionally, the control module comprises a control chip, and the control chip is connected with the acquisition module and the equalization module corresponding to the same single battery through a pin and the channel.

Optionally, the control module is connected with the acquisition module and the equalization module corresponding to the same single battery through two channels respectively.

Optionally, the control module comprises a control chip, the control chip is respectively connected with the acquisition module and the equalization module corresponding to the same single battery through two pins, and the two pins are in one-to-one correspondence with the two channels.

A third aspect of the present disclosure provides a computer readable storage medium having stored thereon computer program instructions which, when executed by a processor, implement the method of the first aspect of the present disclosure.

A fourth aspect of the present disclosure provides an electronic device, comprising:

a computer-readable storage medium according to a third aspect of the present disclosure; and

one or more processors configured to execute the programs in the computer-readable storage medium.

A fifth aspect of the present disclosure provides a vehicle comprising: a battery pack and a battery equalization system according to a fourth aspect of the present disclosure.

Through the technical scheme, the single batteries which need to be balanced are determined according to the voltage change rate of at least one single battery in the battery pack. The single battery to be balanced is not fixed any more according to the SOC value or the load voltage value, the voltage change rate of the single battery is used as the battery information according to which the single battery to be balanced is determined, the battery information according to which the single battery to be balanced is determined is enriched, and a diversified method for determining the single battery to be balanced is provided.

Additional features and advantages of the present disclosure will be set forth in the detailed description which follows.

Drawings

The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated in and constitute a part of this specification, illustrate the disclosure and together with the description serve to explain, but do not limit the disclosure. In the drawings:

FIG. 1 is a schematic diagram of a battery equalization system according to an embodiment of the present disclosure;

FIG. 2 is a schematic diagram of a battery equalization system in which two cells share an equalization module according to an embodiment of the present disclosure;

fig. 3 is a schematic diagram of a battery equalization system of another embodiment of the present disclosure;

fig. 4 is a schematic diagram of a battery equalization system in which two unit batteries share one equalization module according to another embodiment of the present disclosure;

FIG. 5 is a flow chart of a battery equalization method according to an embodiment of the present disclosure;

FIG. 6 is a schematic diagram of a voltage difference between a cell to be equalized and a reference cell according to an embodiment of the disclosure;

fig. 7 is a schematic diagram of a voltage difference between a cell to be equalized and a reference cell according to another embodiment of the present disclosure;

FIG. 8 is an open circuit voltage OCV-residual charge SOC curve of a battery cell according to one embodiment of the disclosure;

fig. 9 is a schematic diagram of a battery internal resistance model according to an embodiment of the present disclosure;

fig. 10 is a schematic diagram of an equalization module of an embodiment of the present disclosure.

Detailed Description

Specific embodiments of the present disclosure are described in detail below with reference to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating and illustrating the disclosure, are not intended to limit the disclosure.

Referring to fig. 1, a schematic diagram of a battery equalization system according to an embodiment of the present disclosure is shown. The battery equalization system includes: a control module 101, an acquisition module 102, an equalization module 103 and a battery pack 104.

In one embodiment, each unit cell corresponds to one acquisition module 102 and one equalization module 103. The acquisition module 102 and the equalization module 103 corresponding to the same single battery are respectively connected with the control module 101 through different control channels. The control module can comprise a control chip, and the control chip is respectively connected with the acquisition module and the equalization module corresponding to the same single battery through two pins, wherein the two pins are in one-to-one correspondence with the two channels.

In this embodiment, the control module 101 controls the acquisition module 102 and the equalization module 103 to conduct time-sharing according to a unit period, and performs battery information acquisition and equalization of batteries respectively, so that battery information acquisition and equalization are performed time-sharing. And when the battery information acquisition and the equalization are performed simultaneously, the influence of the equalization current on the accuracy of the battery information acquisition is avoided.

In one embodiment, referring to fig. 1, each cell in the battery is connected to a collection module 102 and an equalization module 103, respectively. If the battery pack includes N single batteries, the number of the acquisition modules 102 is N, and the number of the equalization modules 103 is N, so that the control module 101 is respectively connected with the N acquisition modules and the N equalization modules through 2×n control channels.

In other embodiments, different cells may share an equalization module, e.g., N cells in a battery pack, may share the same equalization module, or may share one equalization module per a predetermined number (e.g., 2, 3, 5, etc.) of cells, etc. When at least two single batteries in the plurality of single batteries sharing one balancing module need to be balanced, the balancing module is alternately connected with each single battery in the at least two single batteries needing to be balanced in the balancing period of the unit period.

Referring to fig. 2, two single batteries share one balancing module, and when two single batteries sharing one balancing module are required to be balanced, the balancing module is alternately connected with each single battery in a balancing period of a unit period. The alternate connection may be a connection that alternates with a certain period. For example, referring to fig. 2, when the parallel switch 150 on the parallel branch 15 corresponding to one of the two unit batteries 111 is closed for 2s under the control of the control module 14, the parallel switch 150 on the parallel branch 15 corresponding to the other unit battery 111 is opened for 2s under the control of the control module 14. I.e., the parallel switch 150 on the parallel branch 15 corresponding to each of the two unit cells 111, is switched from the closed state to the open state or from the open state to the closed state every two seconds during the equalization period. Therefore, on the basis of time-sharing conduction of the acquisition module and the equalization module, when in an equalization period, the single batteries sharing the same equalization module are alternately connected with the shared equalization module, so that equalization is realized.

Referring to fig. 3, a schematic diagram of a battery equalization system according to another embodiment of the present disclosure is shown.

The battery equalization system includes: a control module 301, an acquisition module 302, an equalization module 303 and a battery pack 304. Wherein, the battery pack 304 includes a plurality of unit cells connected in series. The control module 301 is connected to the acquisition module 302 and the equalization module 303 corresponding to the same unit cell through a control channel 305. The control module is used for connecting the control module with the corresponding sampling module when the single batteries connected with the control module are determined not to be balanced; or, the control module is further configured to, when it is determined that the unit cells connected to the control module need to be equalized, time-sharing multiplex the channel 305 according to a unit period by the acquisition module and the equalization module.

One unit cycle includes: an acquisition period and an equalization period. The control module 301 controls the acquisition module 302 to sample the battery information of the single battery in an acquisition period to obtain the battery information of the single battery. The battery information includes at least one of: voltage, current, temperature, etc. In one embodiment, the battery information may include only the voltage value, whereby the voltage performance parameter of the unit battery may be obtained. In another embodiment, the battery information may also include a voltage value, a current value, a temperature value, and the like, so that performance parameters such as SOC, internal resistance, and a voltage change rate of the unit battery may be obtained.

The control module 301 determines the to-be-equalized single battery to be equalized according to the battery information of the single battery acquired by the acquisition module 302. For the to-be-balanced single battery to be balanced, the control module 301 controls the balancing module corresponding to the to-be-balanced single battery to balance the to-be-balanced single battery in the balancing period.

Therefore, in the embodiment of the disclosure, the acquisition module and the equalization module share the same control channel, the control module controls the acquisition module and the equalization module to multiplex the control channel in a time-sharing way according to a unit period, and the influence of equalization current on the accuracy of battery information acquisition when the battery information acquisition and equalization are performed simultaneously is avoided; on the other hand, compared with the embodiment shown in fig. 1, the number of channels required for the control module chip is reduced, and the hardware cost can be saved.

In one embodiment, a switch K is disposed in a control channel shared by the acquisition module and the equalization module, and the control module 301 is connected to the switch K, and is connected to the acquisition module 302 or the equalization module 303 in a time sharing manner through the control of the switch K. When the switch K is connected with the acquisition module 302, the control module 301 controls the acquisition module 302 to acquire battery information of the single battery in an acquisition period; when the switch K is connected to the equalization module 303, the control module 301 controls the equalization module 303 to equalize the corresponding unit cells.

In one embodiment, referring to fig. 1, each cell in the battery is connected to a collection module 302 and an equalization module 303, respectively. If the battery pack includes N single batteries, the number of the acquisition modules 302 is N, and the number of the equalization modules 303 is N, so that the control module 301 is connected with the acquisition modules and the equalization modules respectively through N control channels.

Referring to fig. 4, an exemplary schematic diagram of two cells sharing an equalization module is shown. When two single batteries sharing one balancing module are needed to be balanced, the balancing module is alternately connected with each single battery in the balancing period of the unit period. The alternate connection may be a connection that alternates with a certain period. Therefore, on the basis of time-sharing conduction of the acquisition module and the equalization module, when in an equalization period, the single batteries sharing the same equalization module are alternately connected with the shared equalization module, so that equalization is realized.

In one embodiment, the collection module may be a voltage collection chip for collecting the voltage of the unit cell during the collection period.

Referring to fig. 5, based on the battery equalization system shown in any of the embodiments of fig. 1, 2, 3 or 4, a battery equalization method according to an embodiment of the present disclosure includes:

in step S51, the voltage change rate of each unit cell in the battery pack is acquired;

in step S52, determining a reference voltage change rate required for equalization judgment according to the voltage change rate of each unit cell in the battery pack;

in step S53, the unit cells to be equalized are determined according to the voltage change rate of at least one unit cell and the reference voltage change rate.

The voltage change rate of the unit cell may be a voltage change amount when a specific physical quantity of the unit cell is changed. For example, in the present disclosure, to charge or discharge a preset amount of electricity to or from a battery cell, a voltage variation amount (dv/dq) of the battery cell; or the single battery is charged or discharged for a preset period of time, and the voltage variation (dv/dt) of the single battery is exemplified.

In one example, the step S51 is not limited to the following two embodiments:

First embodiment: charging or discharging unit electric quantity to each single battery in the battery pack;

Second embodiment: charging or discharging each single battery in the battery pack for unit time; and for each single battery in the battery pack, determining the voltage variation of the single battery as the variation of the voltage value of the single battery along with the unit time of charging/discharging the single battery.

In one embodiment, obtaining the rate of change of the voltage of each cell in the battery pack includes:

and in the charging or discharging process of the battery pack, determining the voltage variation of each single battery by charging or discharging preset electric quantity to each single battery. The voltage variation is the difference between the initial terminal voltage before the preset electric quantity is charged or discharged to the single battery and the final terminal voltage after the preset electric quantity is charged or discharged to the single battery.

And for each single battery in the battery pack, determining that the voltage change rate of the single battery is the ratio of the voltage change quantity of the single battery to the preset electric quantity.

In another embodiment, obtaining the voltage change rate of each unit cell in the battery pack includes:

and in the charging or discharging process of the battery pack, determining the preset time for charging or discharging each single battery, and determining the voltage variation of each single battery. The voltage variation is the difference between the initial terminal voltage before the preset electric quantity is charged or discharged to the single battery and the final terminal voltage after the preset electric quantity is charged or discharged to the single battery;

and for each single battery in the battery pack, determining that the voltage change rate of the single battery is the ratio of the voltage change quantity of the single battery to the preset duration.

In the charging or discharging process of the battery pack, the voltage and electric quantity change conditions of the single battery are recorded, and therefore the voltage change rate of the single battery can be obtained according to the method according to the voltage and electric quantity change conditions.

In step S52, a reference voltage change rate is determined from the voltage change rates of the individual battery cells.

In one embodiment, the voltage change rate of any one of the unit cells in the battery pack may be used as the reference voltage change rate, for example, the voltage change rate of the 2 nd unit cell in the battery pack is used as the reference voltage change rate, or the voltage change rate of the unit cell with the largest voltage change rate in the battery pack, or the voltage change rate of the unit cell with the smallest voltage change rate in the battery pack, or the voltage change rate of the unit cell with the voltage change rate in the battery pack arranged in the middle (for the case that the battery pack includes an odd number of unit cells).

In another embodiment, the reference voltage change rate may also be calculated according to the voltage change rate of each unit cell in the battery pack, for example: an average value of the voltage change rates of the individual unit cells in the battery pack, or an average value of the voltage change rates of two unit cells in the battery pack whose voltage change rates are arranged in the middle (for the case where the battery pack includes an even number of unit cells).

Optionally, step S53 includes:

acquiring an equilibrium starting threshold value;

The equalization-on threshold is a threshold for determining whether equalization is to be performed on any one of the unit cells in the battery pack, that is, a threshold for determining whether any one of the unit cells in the battery pack is a unit cell requiring equalization.

Firstly, at least one single battery is selected from a battery pack, and then the voltage change rate of the selected at least one single battery is differed from the reference voltage change rate, so that the voltage change rate difference value of the selected at least one single battery is obtained. Then comparing the obtained voltage change rate difference value with an equalization opening threshold value, and if the voltage change rate difference value of one single battery is larger than or equal to the equalization opening threshold value, the battery is the single battery which needs equalization; if the voltage change rate difference of one cell is less than the equalization on threshold, the cell is one that does not require equalization.

The reference voltage change rate is different, at least one selected single battery is different, and the process of balancing the single battery to be balanced is different. The reference voltage change rate is the minimum value, the maximum value, and the average value of the voltage change rates of the individual battery cells in the battery pack.

1) In the case where the reference voltage change rate is the minimum value of the voltage change rates of the individual battery cells in the battery pack, the determining the voltage change rate difference between the voltage change rate of the at least one battery cell and the reference voltage change rate required for the equalization judgment includes: determining a voltage change rate difference between the voltage change rate of the following unit cells and a reference voltage change rate required for equalization judgment:

Accordingly, after determining that the cell to be equalized is a cell in which the voltage change rate difference in the at least one cell is greater than or equal to the equalization-on threshold, the method further includes: when the battery pack is in the charging process, controlling the single batteries of which the voltage change rate difference value is larger than or equal to the balance starting threshold value in the at least one single battery to discharge; and when the battery pack is in the discharging process, controlling the single batteries of which the voltage change rate difference value is larger than or equal to the balance starting threshold value in the at least one single battery to charge.

Specifically, when the reference voltage change rate is the minimum value of the voltage change rates of the individual battery cells in the battery pack, only the voltage change rate of the battery cell with the largest voltage change rate in the battery pack is different from the reference voltage change rate, so as to determine whether the battery cell with the largest voltage change rate in the battery pack is the battery cell to be balanced. Such an embodiment can only determine whether a single cell requires equalization.

When the reference voltage change rate is the minimum value of the voltage change rates of the individual battery cells in the battery pack, the voltage change rate of the other battery cells except the battery cell with the minimum voltage change rate in the battery pack can be further reduced from the reference voltage change rate, and whether the other battery cells except the battery cell with the minimum voltage change rate in the battery pack are battery cells which need to be balanced or not can be further judged. This embodiment is a batch judgment method, and can judge whether the other single batteries except the single battery with the minimum voltage change rate in the battery pack are single batteries which need to be balanced or not at one time.

In the case that the reference voltage change rate is the minimum value of the voltage change rates of the individual battery cells in the battery pack, the process of balancing the battery cells to be balanced is as follows:

Considering that the rate of change of voltage is large, on the one hand, the voltage may be caused by the large internal resistance of the battery. Another aspect may be caused by the existence of capacity differences, i.e., initial differences in SOC. The battery with large internal resistance has serious aging, and the voltage of the battery rises quickly in the charging process, so that when the battery pack is in the charging process, the battery cells needing to be balanced are discharged; considering a battery having a large internal resistance, the aging is serious, and the voltage thereof is rapidly reduced during the discharging process, and thus, when the battery pack is in the discharging process, the unit cells requiring equalization are charged.

2) In the case where the reference voltage change rate is the maximum value of the voltage change rates of the individual unit cells in the battery pack, the determining the voltage change rate difference between the voltage change rate of the at least one unit cell and the reference voltage change rate required for the equalization judgment includes: determining a voltage change rate difference between the voltage change rate of the following unit cells and a reference voltage change rate required for equalization judgment:

Accordingly, after determining that the cell to be equalized is a cell in which the voltage change rate difference in the at least one cell is greater than or equal to the equalization-on threshold, the method further includes: when the battery pack is in the charging process, controlling the single batteries of which the voltage change rate difference value is larger than or equal to the balance starting threshold value in the at least one single battery to be charged; and when the battery pack is in the discharging process, controlling the single batteries of which the voltage change rate difference value is larger than or equal to the balance starting threshold value in the at least one single battery to discharge.

Specifically, in the case where the reference voltage change rate is the maximum value of the voltage change rates of the individual battery cells in the battery pack, only the voltage change rate of the battery cell with the smallest voltage change rate in the battery pack may be differed from the reference voltage change rate, so as to determine whether the battery cell with the smallest voltage change rate in the battery pack is the battery cell that needs to be balanced. Such an embodiment can only determine whether a single cell requires equalization.

When the reference voltage change rate is the maximum value of the voltage change rates of the individual battery cells in the battery pack, the voltage change rate of the other battery cells in the battery pack except for the battery cell with the largest voltage change rate can be further reduced from the reference voltage change rate, and whether the other battery cells in the battery pack except for the battery cell with the largest voltage change rate are battery cells which need to be balanced can be further judged. This embodiment is a batch judgment method, and can judge whether the other single batteries except the single battery with the largest voltage change rate in the battery pack are single batteries which need to be balanced at one time.

In the case where the reference voltage change rate is the maximum value of the voltage change rates of the individual battery cells in the battery pack, the process of equalizing the battery cells to be equalized is:

considering that the rate of change of voltage is large, on the one hand, the voltage may be caused by the large internal resistance of the battery. Another aspect may be caused by the existence of capacity differences, i.e., initial differences in SOC. The battery with large internal resistance has serious aging, and the voltage of the battery rises quickly in the charging process, so that when the battery pack is in the charging process, the single battery to be balanced is charged; considering a battery having a large internal resistance, the aging is serious, and the voltage thereof is rapidly reduced during the discharging process, and thus, when the battery pack is in the discharging process, the unit cells requiring equalization are discharged.

3) In the case where the reference voltage change rate is an average value of the voltage change rates of the individual unit cells in the battery pack, the determining a voltage change rate difference between the voltage change rate of the at least one unit cell and the reference voltage change rate required for the equalization judgment includes: and determining a voltage change rate difference value between the voltage change rate of each single battery in the battery pack and the reference voltage change rate.

Accordingly, after determining that the cell to be equalized is a cell in which the voltage change rate difference in the at least one cell is greater than or equal to the equalization-on threshold, the method further includes:

Specifically, when the reference voltage change rate is an average value of the voltage change rates of the individual battery cells in the battery pack, the voltage change rate of the individual battery cells in the battery pack and the reference voltage change rate may be differed, so as to determine whether the individual battery cells in the battery pack are the individual battery cells that need to be balanced. The embodiment is a batch judgment mode, and can judge whether each single battery in the battery pack is a single battery which needs to be balanced or not at one time.

In the case that the reference voltage change rate is an average value of the voltage change rates of the individual battery cells in the battery pack, the process of balancing the battery cells to be balanced is as follows:

considering that the rate of change of voltage is large, on the one hand, the voltage may be caused by the large internal resistance of the battery. Another aspect may be caused by the existence of capacity differences, i.e., initial differences in SOC. The battery with large internal resistance has serious aging, the voltage of the battery rises quickly in the charging process, and the voltage of the battery drops quickly in the discharging process, so that when the battery pack is in the charging process, the battery with the voltage change rate smaller than the average value of the voltage change rates in the battery cells to be balanced is charged, and the battery with the voltage change rate larger than the average value of the voltage change rates in the battery cells to be balanced is discharged; similarly, when the battery pack is in the discharging process, the single battery with the voltage change rate smaller than the average value of the voltage change rates in the single battery to be balanced is discharged, and the single battery with the voltage change rate larger than the average value of the voltage change rates in the single battery to be balanced is charged.

Optionally, in combination with the above embodiments, the method further includes:

After the single battery to be balanced is determined, the target balancing duration of the single battery to be balanced can be determined, and then the single battery to be balanced is balanced according to the determined target balancing duration. The target equalization duration is determined according to the voltage change rate of the single battery to be equalized and the reference voltage change rate.

Optionally, determining the target equalization duration of the unit battery to be equalized according to the voltage change rate of the unit battery to be equalized and the reference voltage change rate includes:

determining a single battery with the smallest difference between the voltage change rate in the battery pack and the reference voltage change rate as a reference battery;

when the initial terminal voltage of the single battery to be balanced is different from the initial terminal voltage of the reference battery, determining the target balancing duration according to the initial terminal voltage of the single battery to be balanced and the initial terminal voltage of the reference battery;

and when the initial terminal voltage of the single battery to be balanced is the same as the initial terminal voltage of the reference battery, determining the target balancing duration according to the final terminal voltage of the single battery to be balanced and the final terminal voltage of the reference battery.

The determining the target equalization duration according to the initial terminal voltage of the to-be-equalized single battery and the initial terminal voltage of the reference battery includes:

determining a first SOC value corresponding to the initial terminal voltage value of the reference battery according to the initial terminal voltage value of the reference battery and an open circuit voltage OCV-residual electric quantity SOC curve of the reference battery;

determining a second SOC value corresponding to the initial terminal voltage value of the single battery to be balanced according to the initial terminal voltage value of the single battery to be balanced and the OCV-SOC curve corresponding to the single battery to be balanced;

and determining the target equalization duration according to the first SOC value and the second SOC value.

Similarly, determining the target equalization duration according to the final terminal voltage of the to-be-equalized unit battery and the final terminal voltage of the reference battery includes:

determining a third SOC value corresponding to the final end voltage value of the reference battery according to the final end voltage value of the reference battery and the OCV-SOC curve of the reference battery;

determining a fourth SOC value corresponding to the final end voltage value of the single battery to be balanced according to the final end voltage value of the single battery to be balanced and an OCV-SOC curve corresponding to the single battery to be balanced;

And determining the target equalization duration of the to-be-equalized single battery according to the third SOC value and the fourth SOC value.

In the embodiments of the present disclosure, the initial terminal voltage is a voltage detected when the battery pack just starts to charge or discharge, or a voltage of a unit cell detected at a certain set detection timing. The final terminal voltage is a voltage obtained by charging or discharging the single battery with a preset electric quantity on the basis of the initial terminal voltage. Or the final terminal voltage is the voltage after the single battery is charged or discharged for a preset period of time on the basis of the initial terminal voltage.

Referring to fig. 6, fig. 6 is a case where there is a difference between the initial terminal voltage of the unit cell to be equalized and the initial terminal voltage of the reference cell. Referring to fig. 7, fig. 7 is a case where there is no difference between the initial terminal voltage of the unit cell to be equalized and the initial terminal voltage of the reference cell, in which case the voltage change rate of the unit cell is mainly caused by the difference in the voltage change rate during the charge or discharge process.

For the case shown in fig. 6, the single battery is in different SOC intervals, the same voltage is changed, and the amount of electricity required to be charged or discharged is different. Therefore, the electric quantity difference of the two single batteries can be determined according to the initial terminal voltage of the two single batteries, and then the target equalization duration of the single batteries to be equalized is determined according to the electric quantity difference of the two single batteries.

Specifically, determining a reference OCV value of the reference battery according to an initial terminal voltage value of the reference battery and an internal resistance value of the reference battery;

determining an SOC value corresponding to the reference OCV value as the first SOC value according to the reference OCV value and an OCV-SOC curve of the reference battery;

determining an OCV value of the single battery to be balanced according to the initial terminal voltage value of the single battery to be balanced and the internal resistance value of the single battery to be balanced;

determining an SOC value corresponding to the OCV value of the single battery to be balanced as the second SOC value according to the OCV-SOC curve of the single battery to be balanced;

as Δq=Δsoc×c _n Determining an electric quantity difference, wherein DeltaQ is the electric quantity difference, deltaSOC is the SOC difference between the first SOC value and the second SOC value, C _n The available capacity of the single battery to be balanced is set;

and determining the target equalization duration according to t=delta Q/I, wherein t is the target equalization duration, and I is the equalization current of the single battery to be equalized.

For the case shown in fig. 7, the target equalization period of the unit cell to be equalized may be determined according to the final terminal voltage of the unit cell to be equalized and the final terminal voltage of the reference cell.

Specifically, determining a reference OCV value of the reference battery according to a final terminal voltage value of the reference battery and an internal resistance value of the reference battery;

determining an SOC value corresponding to the reference OCV value as the third SOC value according to the reference OCV value and an OCV-SOC curve of the reference battery;

determining an OCV value of the single battery to be balanced according to the final end voltage value of the single battery to be balanced and the internal resistance value of the single battery to be balanced;

and determining an SOC value corresponding to the OCV value of the single battery to be balanced as the fourth SOC value according to the OCV-SOC curve of the single battery to be balanced.

As Δq=Δsoc×c _n Determining an electric quantity difference, wherein DeltaQ is the electric quantity difference, deltaSOC is the SOC difference between the third SOC value and the fourth SOC value, C _n The available capacity of the single battery to be balanced is set;

In one embodiment of the present disclosure, the OCV-SOC curve is obtained through an assay. For example, in the process that the SOC value of a certain single battery is changed from 0 to 100%, the open circuit voltage OCV of the primary battery is measured at certain intervals, and then the OCV and the SOC corresponding to each point are in one-to-one correspondence to form an SOC-OCV curve of the single battery. Fig. 8 is a schematic diagram of an OCV-SOC curve of a battery cell. Wherein, OCV is open circuit voltage (Open Circuit Voltage), and SOC is the residual Charge (State of Charge).

The OCV value is an open circuit voltage value of the unit cell, and is different from the load voltage value. Referring to fig. 9 and formula (1), when the battery pack is in a discharge state or a charge state, the unit cell is equivalent to an ideal voltage source connected in series with a resistor R using a battery internal resistance model. Then for a single battery, the sampled voltage value V of the single battery can be calculated according to the formula (1) _L (i.e., the load voltage value) to an open circuit voltage value:

OCV＝V _L +I×R (1)

wherein V is _L The load voltage value acquired by the acquisition module is in the acquisition period; i is the discharge current or the charging current acquired by the acquisition module in the acquisition period; r is the internal resistance value of the single battery.

It should be understood that when the open circuit voltage OCV is measured, the load voltage of the unit cell may be collected first and then converted into the corresponding open circuit voltage OCV according to equation (1).

Alternatively, in another embodiment, the voltage acquired at the moment when the cell to be equalized stops operating and reaches a steady state, or the cell just starts operating is itself or can be regarded as approximately an open circuit voltage, so that the OCV value of the cell to be equalized can be acquired directly in this case.

Alternatively, in another embodiment, the voltage acquired at the instant when the battery to be referenced is stopped and reaches a steady state, or the battery just starts to operate, is itself or can be regarded as approximately an open circuit voltage, so that the OCV value of the reference battery can be acquired directly in this case.

Therefore, the first SOC value, the second SOC value, the third SOC value and the fourth SOC value can be obtained according to the reference voltage value, the internal resistance value of the reference battery and the OCV-SOC curve corresponding to the reference battery.

After obtaining the first SOC value and the second SOC value, the following steps are performed:

as Δq=Δsoc×c _n Determining an electric quantity difference, wherein DeltaQ is the electric quantity difference, deltaSOC is the SOC difference between the first SOC value and the second SOC value, C _n The available capacity of the single battery to be balanced;

and determining a target equalization duration according to t=delta Q/I, wherein t is the target equalization duration, and I is the equalization current of the single battery to be equalized.

Similarly, after obtaining the third SOC value and the fourth SOC value, the following steps are performed:

as Δq=Δsoc×c _n Determining an electric quantity difference, wherein DeltaQ is the electric quantity difference, deltaSOC is the SOC difference between the third SOC value and the fourth SOC value, C _n The available capacity of the single battery to be balanced;

It should be understood that if it is determined that there are no battery cells to be balanced, then it is continuously determined whether there are battery cells to be balanced according to the voltage change rate of at least one battery cell in the battery pack. When it is determined that there are no single batteries to be balanced, the control module may not perform an action, so that the balancing module corresponding to any battery is not turned on.

Referring to fig. 10, a schematic diagram of an equalization module according to an embodiment of the disclosure is shown. And controlling the single batteries to be balanced, and combining the balance judgment. And determining whether the equalization mode of the single battery to be equalized is passive equalization (namely discharging the single battery to be equalized) or active equalization (namely charging the single battery to be equalized) according to the equalization judging step, and conducting the corresponding equalization module.

Referring to fig. 10, for passive equalization, the equalization module includes: and each single battery corresponds to one equalization module, namely, two ends of each single battery are connected with a resistor in parallel.

For the single battery to be balanced which needs to be passively balanced, the control module controls the parallel circuit between the single battery to be balanced and the corresponding resistor to be conducted so as to execute the passive balancing of the single battery. Referring to fig. 10, the control module controls the switch module 812 to conduct, so as to conduct the parallel circuit between the to-be-equalized single battery and the corresponding resistor.

Resistor 811 may be a fixed value resistor or a variable resistor. In one embodiment, the resistor 811 may be a positive temperature coefficient thermistor, which may vary with a change in temperature, so as to adjust an equalization current generated during equalization, thereby automatically adjusting a heating value of the battery equalization system, and finally effectively controlling the temperature of the battery equalization system.

Referring to fig. 10, for active equalization, the equalization module includes a charging branch 94 connected in parallel with each cell 95 in the battery pack, the charging branches 94 are in one-to-one correspondence with the cells 95, and each charging branch 94 is connected to a generator 92, the generator 92 being mechanically connected to the engine 91 by gears.

For the to-be-equalized single battery to be actively equalized, the control module controls the conduction of the charging branch 94 corresponding to the to-be-equalized single battery. When the engine 91 rotates, the generator 92 is driven to generate electricity, so that the electricity generated by the generator 92 is transmitted to the single battery to be balanced, and the electricity of the single battery to be balanced is increased.

Referring to fig. 10, when the generator 92 is an alternator, the balancing module further comprises a rectifier 93 in series with the generator 92, each charging branch 130 being connected in series with said rectifier 132. After converting the alternating current generated by the generator 92 into direct current by the rectifier 93, the generator 92 can be enabled to charge the unit cells to be equalized.

Referring to fig. 10, the control module may perform active equalization of the unit cells to be equalized by controlling the switch 96 corresponding to the unit cells to be equalized to be turned on, so that the charging branches corresponding to the unit cells to be equalized are turned on.

In other embodiments, in addition to the battery cells being charged by the generator as shown in fig. 10, the battery cells to be balanced may be charged by a starting battery in the whole vehicle.

In another embodiment, besides the parallel resistor and the single battery to be balanced as shown in fig. 10, the single battery to be balanced and the starting battery of the whole vehicle can be connected in parallel, and the electric quantity discharged by the single battery to be balanced is charged into the starting battery, so that the balance of the single battery to be balanced is realized, and meanwhile, the waste of energy is effectively avoided.

As described above, in the embodiment of the present disclosure, a plurality of unit cells may share one balancing module, and when at least two unit cells need to be balanced among a plurality of unit cells sharing one balancing module, the balancing module is alternately connected with each unit cell of the at least two unit cells that need to be balanced, and performs balancing respectively.

Correspondingly, the embodiment of the disclosure also provides a vehicle, which comprises the battery balancing system.

Accordingly, embodiments of the present disclosure also provide a computer-readable storage medium having stored thereon computer program instructions that, when executed by a processor, implement the above-described battery equalization method.

Accordingly, an embodiment of the present disclosure further provides an electronic device, including: the aforementioned computer-readable storage medium; and one or more processors configured to execute the program in the computer-readable storage medium.

The preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings, but the present disclosure is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solutions of the present disclosure within the scope of the technical concept of the present disclosure, and all the simple modifications belong to the protection scope of the present disclosure.

In addition, the specific features described in the above embodiments may be combined in any suitable manner without contradiction. The various possible combinations are not described further in this disclosure in order to avoid unnecessary repetition.

Claims

1. A battery equalization method, comprising:

obtaining the voltage change rate of each single battery in the battery pack;

determining the single battery to be balanced according to the voltage change rate of at least one single battery and the reference voltage change rate,

Wherein, according to the voltage change rate of at least one single battery and the reference voltage change rate, determining the single battery to be balanced comprises:

acquiring an equilibrium starting threshold value;

determining the single battery with the voltage change rate difference value larger than or equal to the balance starting threshold value in the at least one single battery as the single battery needing balance;

the determining the reference voltage change rate required by the equalization judgment according to the voltage change rate of each single battery in the battery pack comprises the following steps: determining the minimum value of the voltage change rates of all the single batteries in the battery pack as the reference voltage change rate;

the determining a voltage change rate difference between the voltage change rate of the at least one unit cell and the reference voltage change rate includes: determining a voltage change rate difference between a voltage change rate of the following unit cells and the reference voltage change rate: the single battery with the largest voltage change rate in the battery pack; or other single batteries except the single battery with the voltage change rate of the minimum value in the battery pack;

Or,

the determining the reference voltage change rate required by the equalization judgment according to the voltage change rate of each single battery in the battery pack comprises the following steps: determining the maximum value of the voltage change rates of all the single batteries in the battery pack as the reference voltage change rate;

the determining a voltage change rate difference between the voltage change rate of the at least one unit cell and the reference voltage change rate includes: determining a voltage change rate difference between a voltage change rate of the following unit cells and the reference voltage change rate: the single battery with the minimum voltage change rate in the battery pack; or other single batteries except the single battery with the maximum voltage change rate in the battery pack;

or,

the determining the reference voltage change rate required by the equalization judgment according to the voltage change rate of each single battery in the battery pack comprises the following steps: determining an average value of the voltage change rates of the individual battery cells in the battery pack as the reference voltage change rate;

the determining a voltage change rate difference between the voltage change rate of the at least one unit cell and the reference voltage change rate includes: determining a voltage change rate difference value between the voltage change rate of each single battery in the battery pack and the reference voltage change rate;

Wherein after determining the cell to be equalized according to the voltage change rate of the at least one cell and the reference voltage change rate, the method further comprises:

controlling the equalization of the single batteries to be equalized according to the target equalization duration of the single batteries to be equalized;

the determining, according to the voltage change rate of the to-be-balanced unit battery and the reference voltage change rate, a target balancing duration of the to-be-balanced unit battery includes:

when the initial terminal voltage of the single battery to be balanced is the same as the initial terminal voltage of the reference battery, determining the target balancing duration according to the final terminal voltage of the single battery to be balanced and the final terminal voltage of the reference battery;

The determining the target equalization duration according to the initial terminal voltage of the single battery to be equalized and the initial terminal voltage of the reference battery includes:

determining a first SOC value corresponding to the initial terminal voltage value of the reference battery according to the initial terminal voltage value of the reference battery and an OCV-SOC curve of the reference battery;

determining the target equalization duration according to the first SOC value and the second SOC value;

the determining the target equalization duration according to the final terminal voltage of the single battery to be equalized and the final terminal voltage of the reference battery includes:

determining a fourth SOC value corresponding to the final end voltage value of the single battery to be balanced according to the final end voltage value of the single battery to be balanced and the OCV-SOC curve corresponding to the single battery to be balanced;

And determining the target equalization duration of the single battery to be equalized according to the third SOC value and the fourth SOC value.

2. The method according to claim 1, wherein a minimum value of the voltage change rates of the individual cells in the battery pack is determined as the reference voltage change rate, and after the cells having the voltage change rate difference value of greater than or equal to the balance on threshold in the at least one cell are determined as the cells requiring balance, the method further comprises:

3. The method according to claim 1, wherein a maximum value of the voltage change rates of the individual cells in the battery pack is determined as the reference voltage change rate, and after the cells having the voltage change rate difference value of greater than or equal to the balance on threshold in the at least one cell are determined as the cells requiring balance, the method further comprises:

4. The method according to claim 1, wherein an average value of the voltage change rates of the individual cells in the battery pack is determined as the reference voltage change rate, and after the cells having the voltage change rate difference value of greater than or equal to the balance on threshold in the at least one cell are determined as the cells requiring balance, the method further comprises:

5. The method of claim 1, wherein the obtaining the voltage change rate of each unit cell in the battery pack comprises:

6. The method of claim 1, wherein the obtaining the voltage change rate of each unit cell in the battery pack comprises:

charging or discharging each single battery in the battery pack for unit time;

7. A battery equalization system, comprising: the balance module, the acquisition module and the control module,

The balancing module is used for balancing the single batteries to be balanced,

wherein, the control module is used for:

acquiring an equilibrium starting threshold value;

wherein, the control module is used for:

the control module is used for:

the equalization module is used for:

equalizing the single batteries to be equalized according to the target equalizing time of the single batteries to be equalized;

Wherein, the control module is used for:

8. The battery equalization system of claim 7, wherein the control module is configured to:

9. The battery equalization system of claim 7, wherein the control module is configured to:

charging or discharging each single battery in the battery pack for unit time;

10. The battery equalization system of claim 7, wherein the control module is connected to the acquisition module and the equalization module corresponding to the same cell through a channel, and the control module is configured to control the control module to be connected to the corresponding sampling module when it is determined that the cell connected to the control module does not need to be equalized; or,

11. The battery equalization system of claim 10, wherein the control module comprises a control chip connected to the acquisition module and the equalization module corresponding to the same cell through one pin and one channel.

12. The battery equalization system of claim 7, wherein the control module is connected to the acquisition module and the equalization module, respectively, corresponding to the same cell, through two channels.

13. The battery equalization system of claim 12, wherein the control module comprises a control chip connected to the acquisition module and the equalization module corresponding to the same cell through two pins, respectively, the two pins being in one-to-one correspondence with the two channels.

14. A computer readable storage medium having stored thereon computer program instructions, which when executed by a processor, implement the method of any of claims 1-6.

15. An electronic device, comprising:

the computer readable storage medium recited in claim 14; and

16. A vehicle, characterized in that the vehicle comprises: battery pack and battery equalization system according to any of claims 7-13.