DE102018218579A1 - Method and device for detecting a defect in a battery in a low-voltage electrical system of an electric vehicle - Google Patents

Abstract

The present invention provides a method for detecting a defect in a battery (B) in a low-voltage electrical system of an electric vehicle. The method comprises the step of applying (S1) an electrical consumer (L) of the electric vehicle to the low-voltage electrical system. Furthermore, the method comprises the step of detecting (S2) a resulting voltage dip in the battery (B) of the low-voltage electrical system with a voltage sensor (V). The method further comprises the step of determining (S3) the defect when the detected voltage drop fulfills a predetermined criterion. The present invention also provides a device for detecting a defect in a battery (B) in a low-voltage electrical system of an electric vehicle.

Description

State of the art

In conventional vehicles, for example in vehicles with an internal combustion engine, a diagnosis of the low-voltage electrical system battery (NSP-BN battery), usually 12V or 24V nominal voltage, takes place when the vehicle is started. If the vehicle starts successfully, it can be assumed that the NSP-BN battery is OK. If the NSP-BN battery is defective or worn, the vehicle will no longer start because the NSP-BN battery is no longer able to provide the required current for the starter (starter). The vehicle remains in a safe state (the engine does not start) and can no longer be moved. The driver can clearly see that the vehicle or the NSP-BN battery must be checked in a workshop.

In electric vehicles, this high level of stress is lacking due to the starting process, for example due to the starter's current consumption. The electric vehicle can also be started with an almost defective or worn NSP-BN battery, since the currents required during the starting process of an electric vehicle are relatively low and shortly after the electric vehicle starts, the low-voltage electrical system of the electric vehicle through the DC / DC converter is supported or supplied. This has the disadvantage that a defective NSP-BN battery, for example 12V, is only recognized when it is finally defective. In the worst case, a defective NSP-BN battery is not recognized and, if the DC / DC converter fails at the same time, the NSP-BN breaks in. This can lead to a critical driving situation. Neither the impending defect (NSP-BN battery weak / deeply discharged) nor the defect that has occurred (NSP-BN battery without appreciable capacity and so low-impedance that the DC / DC converter can just adequately support the network) is recognized . A failure of the DC / DC converter that then occurs can lead to a critical driving situation (possibly and possibly endangering road users).

Circuit arrangements for checking an operating state of a battery are, for example, from US Pat DE 10 2014 003309 A1 known.

Disclosure of the invention

The present invention provides a method and a device for detecting a defect in a battery in a low-voltage electrical system of an electric vehicle according to independent claims 1 and 10, respectively.

The present invention provides a method for detecting a defect in a battery in a low-voltage electrical system of an electric vehicle, with a first step of applying an electrical consumer of the electrical vehicle to the low-voltage electrical system. Furthermore, the method comprises the second step of detecting a resulting voltage dip in the battery of the low-voltage electrical system using a voltage sensor. Furthermore, the method comprises the third step of determining the defect if the detected voltage drop fulfills a predetermined criterion.

Furthermore, the present invention provides a device for detecting a defect in a battery in a low-voltage electrical system of an electric vehicle, with a control device, a switching device, an electrical consumer and a voltage sensor, which is designed such that an electrical consumer is switched by a switching device with a battery Low-voltage electrical system of the electric vehicle is electrically connected and the switching device is actuated via a control device. Furthermore, a resulting voltage drop in the battery of the low-voltage electrical system is detected with a voltage sensor and a defect in the battery is determined if the detected voltage drop fulfills a predetermined criterion.

Furthermore, the present invention provides a computer program product according to independent claim 9.

The present invention relates to a computer program product with a program code stored on a machine-readable carrier for carrying out a method according to claims 1 to 8 when the program runs on a control device of the electric vehicle.

The computer program product can be executed with a control device. The control device can be a control device of an electric vehicle, comprising a processor and a memory. In addition, the control device can be a microcontroller or a computer.

Advantages of the invention

The method and the device for detecting a defect in a battery according to the present invention enable existing components in electric vehicles to be used for diagnosing the NSP-BN battery. Even before the low-voltage on-board electrical system (NSP-BN) is supported by the DC / DC converter, a previously defined load, for example an electrical consumer of the electrical Vehicle to which the NSP-BN battery is attached to detect a possible defect in the NSP-BN battery. The 12 V consumers in an electric vehicle can advantageously be used as an electrical load, in which a measurable and correspondingly noticeable drop in voltage occurs, for example on the rear window heater or the seat heater. Additional consumers, which are only switched on or off again specifically for diagnosis, are not required.

Furthermore, existing electrical consumers and / or controllable loads, for example bidirectional DC / DC converters, advantageously offer the possibility of identifying relevant properties of the battery during a start or over a sequence of several starts. These include the state of health (SOH) and the state of charge (SOC) of the battery. This can be used, on the one hand, to predict future battery behavior and, on the other hand, to derive remedial measures, for example battery training, controlled cycling and the creation of defined charging / discharging profiles.

The idea on which the present invention is based is therefore to use existing components and thus to additionally save hardware components, such as an intelligent 12 V battery sensor. Systems known in the prior art require an intelligent battery sensor to determine the current and the current voltage. In the present invention, existing voltage sensors of the electric vehicle, for example the voltage sensors of the vehicle control units or the DC / DC converter, are advantageously used individually or in combination in order to detect a voltage drop beyond a predetermined criterion and thus to determine a defect in the battery .

In an advantageous manner, the method and the device according to the present invention can also be used for batteries with a 24V or 48V nominal voltage.

It is also advantageous that the battery of the electric vehicle can be dimensioned smaller and scarcer, since a defect in the battery is determined before the electric vehicle starts, and thus no longer necessary battery remaining capacities, as a reserve for the safe operation of the electric vehicle are necessary.

The NSP-BN battery is advantageously diagnosed reliably, which ensures the necessary redundancy of the 12V power supply. This ensures that in the event of a failure if the previous defect of the 12 V battery is not recognized, the function of electrical braking and steering assistance and possibly other important vehicle functions do not cease.

Increased wear can also be diagnosed and displayed to the vehicle driver. The display enables the 12V battery to be replaced early and the number of technical downtimes and non-starting vehicles can be greatly reduced. The increased wear occurs when the battery has reached the end of its useful life and needs to be replaced.

Preferred developments are the subject of the respective subclaims.

According to a preferred embodiment, the first step and the second step are repeated at least one more time and the defect in the battery is determined in the third step if the voltage drop repeatedly fulfills the predetermined criterion.
This embodiment is advantageous in that the condition of the battery and thus the wear and / or the defect can also be determined via a trend.

According to a preferred embodiment, the defect in the battery of the low-voltage electrical system is determined before the electric vehicle is started.

This embodiment is advantageous in that a defect in the battery can be determined before the electric vehicle is started and thus before the start of use. Critical driving situations due to battery failure while driving can be better avoided.

According to a preferred embodiment, the defect in the battery of the low-voltage electrical system is determined after a DC / DC converter of the electric vehicle has been switched off.

This embodiment is advantageous in that the battery of the electric vehicle can be checked even with a long driving cycle time.

DC / DC converters in LV / HV operation are best suited to apply a short, high load to the NSP-BN without great energy loss.

According to a preferred embodiment, the defect in the battery of the low-voltage electrical system is determined during a diagnostic phase and the predefined criterion includes a Break in and a recovery of the battery voltage in the diagnostic phase.

This embodiment is advantageous in that the drop in voltage represents the condition and thus possible wear of the battery.

According to a preferred embodiment, the electrical consumer of the electric vehicle is applied to the low-voltage electrical system in a pulsed manner.

This embodiment is advantageous in that the battery of the electric vehicle can be tested more gently and has a longer service life.

According to a preferred embodiment, a warning message is output when the detected voltage drop fulfills a predetermined criterion.

This embodiment is advantageous in that the battery of the electric vehicle is worn out but still provides power that the wear and tear of the battery is signaled to the vehicle driver and he initiates appropriate measures, for example, to have the battery replaced before a defect in the battery occurs.

According to a preferred embodiment, the drive of the electric vehicle is deactivated when the detected voltage drop fulfills a predetermined criterion.

This embodiment is advantageous in that when a defect in the battery is determined that the further use of the electric vehicle is prevented in order to avoid possible critical driving situations.

According to a preferred embodiment, the wear of the battery is determined, the voltage drops in the battery being recorded over the service life of the battery.

The state of health of the battery can thus advantageously be determined over the period of use.

Figure list

• 1 eine schematische Darstellung zur Erläuterung einer Vorrichtung 10 zur Erkennung eines Defekts einer Batterie B in einem Niederspannungsbordnetz eines elektrischen Fahrzeugs gemäß einer Ausführungsform der vorliegenden Erfindung;
• 2 eine schematische Darstellung zur Erläuterung eines Verfahrens zur Erkennung eines Defekts einer Batterie B in einem Niederspannungsbordnetz eines elektrischen Fahrzeugs gemäß einer Ausführungsform der vorliegenden Erfindung;
• 3 eine schematische Darstellung zur Erläuterung eines ersten Spannungsverlaufs 1 während der Diagnose bei einer funktionierenden Batterie B;
• 4 eine schematische Darstellung zur Erläuterung eines zweiten Spannungsverlaufs 2 während der Diagnose bei einer verschlissenen Batterie B;
• 5 eine schematische Darstellung zur Erläuterung eines dritten Spannungsverlaufs 3 während der Diagnose bei einer defekten Batterie B;

Show it:

• 1 a schematic representation to explain a device 10th to detect a defect in a battery B in a low-voltage electrical system of an electric vehicle according to an embodiment of the present invention;
• 2nd a schematic representation to explain a method for detecting a defect in a battery B in a low-voltage electrical system of an electric vehicle according to an embodiment of the present invention;
• 3rd a schematic representation for explaining a first voltage curve 1 during the diagnosis of a working battery B ;
• 4th a schematic representation to explain a second voltage curve 2nd during the diagnosis of a worn battery B ;
• 5 a schematic representation to explain a third voltage curve 3rd during the diagnosis of a defective battery B ;

In the figures, elements that are the same or have the same function are provided with the same reference symbols.

Description of the embodiments

1 is a schematic diagram for explaining an apparatus 10th to detect a defect in a battery B in a low-voltage electrical system of an electric vehicle.

In 1 denotes reference numerals SC a switching device, which with a battery B , typically a 12V low voltage on-board battery (NSP-BN battery) is connected. The switching device SC is set up an electrical consumer L , preferably an existing electrical component of the electric vehicle with the battery B to electrically connect the low-voltage electrical system of the electric vehicle. All electrical components of the electric vehicle can be used as electrical consumers, by means of which a noticeable voltage drop can be generated, for example the rear window heater or the seat heater. The switching device SC is with a control device ST connected. The control device ST actuates the switching device SC .

The device 10th is still set up a voltage sensor V parallel to the electrical consumer L to switch to a resulting voltage drop in the battery B of the low-voltage electrical system (NSP-BN). In the event of a voltage drop, the battery is no longer able to provide electricity B to understand. This depends on the switched electrical consumer L and the nominal voltage of the battery B .

The device 10th is still set up the defect of the battery B to be determined when the detected voltage range fulfills a given criterion. The specified criterion depends on the battery used B the low-voltage electrical system of the electric vehicle. The device 10th can be used to determine a defect in batteries B with a nominal voltage of 12V, 24V and 48V can be used.

The device 10th The present invention enables a defect in the battery B in the NSP-BN, for example a short circuit, a worn battery B due to the service life, deep discharge or damage due to thermal stress, can be diagnosed safely without using an intelligent battery sensor as a voltage sensor V or an additional electrical consumer L must be installed in the electric vehicle. If a defect in the battery is found, the vehicle can be brought into a safe state, for example the drive torque is denied. Furthermore, the defect can be shown to the vehicle driver, for example in a head-up display or on a multifunctional display of the electric vehicle.

In an alternative embodiment, the DC / DC converter can be used as support for the 12V battery in the case of electric vehicles with a long driving cycle time and which have a high power consumption B be switched off. This would result in all electrical consumers being switched on L about the battery B be supplied and a voltage drop in the battery B cause. Thus the diagnosis D can also be carried out while the vehicle is stationary by switching off the charging function of the DC / DC converter. This is possible as long as there are no objections to safety, for example the danger to other road users.

In one embodiment, this can be done with existing electrical consumers L Diagnostics to be carried out in pulse form, similar to a start pulse for conventional starters, in which a high maximum current flows in the order of a few 10 ms, or as quasi-steady-state diagnostics with rather medium currents over a somewhat longer period. The length of the pulse depends on the amplitude of the voltage dip with the electrical consumers L can be reached.

2nd is a schematic diagram for explaining a method for detecting a defect in a battery B in a low-voltage electrical system of an electric vehicle.

The procedure for detecting a defect in a battery B in a low-voltage electrical system of an electric vehicle comprises before the electric vehicle is started in a first step S1 creating a defined electrical consumer L of the electric vehicle to the low-voltage electrical system of the electric vehicle. The electrical consumer L can be, for example, a bidirectional DC / DC converter, the rear window heater or seat heater of the electric vehicle.

Due to the applied consumer, the voltage on the 12V side of the battery B collapse or decrease by a certain value. The value of the voltage dip depends on the system and the load. The voltage drop in the battery B of the low-voltage on-board network is controlled by a voltage sensor V in a second step S2 detected. The voltage sensor is preferably V an existing voltage sensor V the DC / DC converter or a vehicle control unit and can be used individually or in combination to determine the voltage drop.

If the detected voltage drop meets a specified criterion, it can be assumed that the battery B is broken. The defect of the battery B is in a third step S3 certainly. If there is a defect, the vehicle start can be aborted or the electric vehicle can be switched to a safe state (drive without function) and this can be signaled to the driver.

3rd is a schematic representation for explaining a first voltage curve 1 during diagnosis D with a working battery B .

In 3rd is the first voltage curve 1 during diagnosis D a battery B , especially with a functioning battery B , shown. The abscissa axis represents the time course of the first voltage course 1 in seconds [s] and the ordinate axis the voltage drop during the diagnosis D in volts [ V ]. The schematic representation is divided into three voltage ranges 11 , 12th and 13 . The tension range 11 is the first voltage range at which the battery B is rated as working. The second area of tension 12th is the voltage range at which the battery B is rated as worn. The third area of tension 13 is the voltage range at which the battery B has a defect.

In 3rd becomes an electrical consumer before starting the electric vehicle L through the switching device SC switched into the NSP-BN of the electric vehicle. The first course of tension 1 exhibits a voltage drop within the diagnostic phase D on. The Voltage drop does not exceed the first voltage range 11 , as a predefined criterion for a functioning battery B . The battery also recovers within the diagnostic phase. For the battery B according to the first voltage curve 1 the 3rd thus no defect is determined and the battery B rated as okay. The areas of tension 11 , 12th and 13 must be adjusted according to the nominal voltage of the battery used (12V, 24V, 48V).

It is not the absolute voltage drop that is assessed during the diagnosis, but rather the relative voltage value and how it is within the diagnosis phase D recovered again when the electrical consumer L from the NSP-BN of the electric vehicle. The predefined criterion thus indicates the maximum amplitude of the voltage dip and the duration (diagnosis phase) of the voltage dip until the maximum amplitude is reached and the battery is recovered B , until the voltage that is still possible is reached.

4th is a schematic representation for explaining a second voltage curve 2nd during diagnosis D if the battery is worn out B .

In 4th is the second voltage curve 2nd during diagnosis D a battery B , especially if the battery is worn out B , shown. Before the starting process, a defined electrical consumer is created L through the switching device SC switched into the NSP-BN of the electric vehicle. The second course of tension 2nd exhibits a voltage drop within the diagnostic phase D on. The voltage drop exceeds the first voltage range 11 , as a predefined criterion for a functioning battery B . Because of the electrical consumer L the voltage on the 12V side drops by a certain value (depending on the system and load) and reaches the second voltage range 12th , as a predefined criterion for a worn battery B . After switching off the electrical consumer L the voltage of the battery recovers B again and reaches the first voltage range 11 .

This diagnosis can be carried out repeatedly over several measurements. If the second voltage range is repeated during the diagnosis 12th reached, it can be assumed that the battery B is worn out. In this scenario, further use of the electric vehicle is not prohibited. The vehicle driver is advised, for example, that he should go to a workshop with the electric vehicle, since the worn-out battery causes the electric vehicle to come to a standstill B threatens.

In one embodiment, the battery B rated as worn if the second voltage range 12th is achieved in two consecutive diagnoses.

In an alternative embodiment, the battery B rated as worn if the second voltage range 12th successive diagnoses, determined by a counter, are repeatedly achieved. The counter value of the counter can be reached by reaching the first voltage range 11 reset to its starting value so that the count for the repeated diagnosis starts again. Only when the defined meter reading is reached is the vehicle driver warned and / or the electric vehicle is put into the safe state (drive without function).

5 is a schematic representation for explaining a third voltage curve 3rd during diagnosis D if the battery is defective B .

In 5 is the third voltage curve 3rd during diagnosis D a battery B , especially if the battery is defective B , shown. Before the starting process, a defined electrical consumer is created L through the switching device SC switched into the NSP-BN of the electric vehicle. The third course of tension 3rd exhibits a voltage drop within the diagnostic phase D on. The voltage drop exceeds the first voltage range 11 , as a predefined criterion for a functioning battery B and the second voltage range 12th , as a predefined criterion for a worn battery B . Because of the electrical consumer L the voltage on the 12V side drops by a certain value (depending on the system and load) and reaches the third voltage range 13 , as a predefined criterion for a defective battery B . After switching off the electrical consumer L the voltage of the battery recovers B again and reaches the first voltage range 11 . The voltage dip in 5 an extreme slump that suggests that the battery B no longer the necessary electricity for the electrical consumer L can provide. This will result in a defect for the battery B certainly. If the battery is worn or defective B the voltage drop is much larger than with an intact battery B . In addition, the battery can recover more slowly.

In 5 is the beginning of the third voltage curve 3rd in the first voltage range 11 . A defective battery can, however, already have a limited voltage, so that the third voltage curve 3rd already in the second voltage range 12th when creating the electrical consumer L can lie.

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102014003309 A1 [0003]

Claims (10)

Method for detecting a defect in a battery (B) in a low-voltage electrical system of an electric vehicle, comprising the steps: - Applying (S1) an electrical consumer (L) of the electric vehicle to the low-voltage electrical system; - Detecting (S2) a resulting voltage dip in the battery (B) of the low-voltage electrical system with a voltage sensor (V); and - Determine (S3) the defect if the detected voltage drop fulfills a predetermined criterion. Procedure according to Claim 1 , wherein the first step (S1) and the second step (S2) are repeated at least one more time and the defect in the battery (B) is determined in the third step (S3) if the voltage drop repeatedly fulfills the predetermined criterion. Procedure according to Claim 1 or 2nd , wherein the determination of the defect of the battery (B) of the low-voltage electrical system is carried out before the start of the electric vehicle. Procedure according to Claim 1 or 2nd , wherein the defect in the battery (B) of the low-voltage electrical system is determined after a DC / DC converter of the electric vehicle has been switched off. Method according to one of the preceding Claims 1 to 4th , wherein the defect in the battery (B) of the low-voltage electrical system is determined during a diagnostic phase (D) and the predetermined criterion comprises a drop in and recovery of the voltage of the battery (B) in the diagnostic phase (D). Method according to one of the preceding Claims 1 to 5 , wherein the electrical consumer (L) of the electric vehicle is applied to the low-voltage electrical system in a pulsed manner. Method according to one of the preceding Claims 1 to 6 , with a warning message being issued if the detected voltage drop fulfills the specified criterion. Method according to one of the preceding Claims 1 to 7 , wherein the drive of the electric vehicle is deactivated when the detected voltage drop fulfills the predetermined criterion. Computer program product with a program code stored on a machine-readable carrier for carrying out a method according to the Claims 1 to 8th when the program runs on a control device (ST) of the electric vehicle. Device (10) for detecting a defect in a battery (B) in a low-voltage electrical system of an electric vehicle, with a control device (ST), a switching device (SC), an electrical load (L) and a voltage sensor (V), which is designed in this way that - An electrical consumer (L) is electrically connected by a switching device (SC) to a battery (B) of a low-voltage electrical system of the electric vehicle, the switching device (SC) being actuated by a control device (ST); - A resulting voltage drop in the battery (B) of the low-voltage electrical system can be detected with a voltage sensor (V); - A defect in the battery (B) can be determined when the detected voltage drop fulfills a predetermined criterion.

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