METHOD FOR BACKING UP AND RESTORING A BATTERY, VEHICLE AND PROGRAM MANAGEMENT SYSTEM BASED ON SUCH A METHOD

Abstract

The invention relates to a method for backing up and restoring a battery management system for a battery that includes non-volatile memory. The method comprises the following steps: - a determination step (E1) in which electrical tests are performed on the battery and / or at least one model is used to determine driving data; - a backup step (E2) in which vehicle usage data, as well as driving data, are saved in a backup memory; - in the event of a fault or recycling of the non-volatile memory (H), a restoration step (E3) in which the vehicle usage data, as well as driving data, are restored from the backup memory to the non-volatile memory. The invention also relates to a program and a vehicle based on such a method. Figure 1

Description

Title of the invention: METHOD FOR BACKING UP AND RESTORING A BATTERY MANAGEMENT SYSTEM, VEHICLE AND PROGRAM BASED ON SUCH A METHOD

[0001] The invention relates to the field of lithium-ion battery management systems (or "BMS" for "battery management system" in English), and of controls / commands of lithium-ion batteries (traction or stationary).

[0002] A battery management system for managing battery functions and safety is necessary to operate the battery optimally without failure or risk to the user.

[0003] It is common to have hardware defects in the BMS that require its complete replacement, or replacement of defective parts to reuse the BMS.

[0004] The solutions of the prior art are either a change of the complete battery; or to start again with default values ​​corresponding to a new battery; or to remove the battery from the vehicle to carry out a complete characterization campaign.

[0005] Unfortunately, changing the entire battery due to a BMS hardware problem involves a loss of other functional hardware and software of the battery. Starting from blank values ​​by relying on user usage to reconverge the values ​​of the state of charge and health indicators, can accelerate aging due to a performance permission equivalent to a new condition, but above all is too risky for the safety of the battery because it can cause a deposit of metallic lithium (or "Lithium plating" in English) during regeneration if the regeneration current is overestimated in the case of regenerative braking for example.

[0006] An objective of the present invention is to remedy the defects of the prior art, and in particular to propose a solution making it possible to reuse as many hardware parts as possible in the event of a BMS defect, while limiting the aging of the battery.

[0007] To achieve this objective, the invention proposes a method for backing up and restoring a battery management system of a battery which comprises a non-volatile memory, the method comprising the following steps: - a determination step in which at least one electrical test is carried out on the battery and / or at least one model is used, to determine driving data; - a backup step in which usage data is saved from the vehicle, as well as driving data, in a backup memory; - in the event of a fault or recycling of the non-volatile memory, a restoration step in which the vehicle usage data, as well as the driving data, are restored from the backup memory to the non-volatile memory.

[0008] Advantageously, the invention makes it possible to have a methodology for learning the values ​​of the battery usage history in the event of non-reversible memory loss to ensure the continuity of its use without security risk and damage to its durability.

[0009] According to a variant, the battery has a state of charge, a state of health in capacity, a state of health in resistance, and the battery management system comprises values ​​of states of charge and temperature, the driving data comprises at least one of the state of charge, the state of health in capacity, the state of health in resistance, and the usage data comprises charged energies and discharged energies and / or matrices of states of charge and temperatures at different operating points.

[0010] This allows for sufficient data on usage history and battery status.

[0011] According to a variant, the battery management system comprises values ​​of energy consumption per distance, distances traveled, and energy efficiency of the battery, and the discharged energies are determined from the energy consumption per distance and the distances traveled; and the charged energies are determined from the discharged energies and the energy efficiency of the battery.

[0012] This makes it possible to easily and precisely evaluate the state of health via the charged and discharged energies.

[0013] According to a variant, the battery has a state of charge, and the driving data comprises the state of charge, and said electrical test comprises a relaxation and a restart of the battery, then an estimation of the state of charge from voltage measurements; or a complete charge or discharge and a verification of the state of charge.

[0014] This allows for a precise evaluation of the driving data depending on the battery technology used.

[0015] According to a variant, in which the battery has a capacity health status at an ambient temperature, and the driving data comprises the capacity health status, and said electrical test comprises a partial charge or discharge preceded and followed by a relaxation to determine the capacity and the capacity health status; or a discharge followed by a full charge to determine the charged energy and deduce the capacity health status therefrom.

[0016] This makes it possible to easily and precisely determine the state of health in capacity.

[0017] According to a variant, the driving data comprises the capacity health status and said model comprises a capacity health status model as a function of chemical parameters of the battery and the ambient temperature.

[0018] This makes it possible to easily and accurately determine the state of health in capacity in another way.

[0019] According to a variant, the battery has a resistance health status, and the driving data comprises the resistance health status, and said electrical test comprises an application of current pulsation and a measurement of battery cell voltage variation to determine the current resistance, and the resistance health status.

[0020] This makes it possible to easily and precisely determine the state of health in resistance.

[0021] According to a variant, the model comprises an equivalence curve of the state of health in resistance compared to the state of health in capacity and temperature.

[0022] This makes it possible to easily and precisely determine the state of health in resistance in another way.

[0023] The invention further relates to a computer program comprising program code instructions for executing the steps of the backup and restoration method according to the invention, when said program operates on a computer.

[0024] Another subject of the invention relates to a motor vehicle comprising a battery and a battery management system of the battery, which comprises a non-volatile memory, characterized in that it further comprises a control unit implementing a backup and restoration method according to the invention.

[0025] The invention will be further detailed by the description of non-limiting embodiments, and on the basis of the attached [Fig.l] schematically illustrating a backup and restoration method according to the invention.

[0026] The invention relates to a method for backing up and restoring a battery management system of a battery which comprises non-volatile memory, illustrated in [Fig.l].

[0027] The method comprises a determination step E1 for determining driving data; and a saving step E2 for saving vehicle usage data, as well as the driving data, in a backup memory.

[0028] In the event of a fault or recycling of the non-volatile memory (step H), a restoration step E3 is implemented to restore the vehicle usage data and the driving data from the backup memory to the non-volatile memory.

[0029] The method comprises a reconstruction of the history of the non-volatile memory of the battery to avoid its replacement. The invention proposes a simplified methodology for filling the following quantities of the non-volatile memory in the battery management system: - the state of charge; - the state of health in capacity; - the state of health in resistance; - a parking usage data matrix; - a driving usage data matrix; - a history of the energies discharged and charged in kilowatt hours.

[0030] The process is carried out either with rapid electrical testing procedures and / or with so-called "durability" models established offline (for example as a supplement). Car manufacturers or battery chemistry suppliers already have these models.

[0031] In addition to the safety issues that this procedure involves, the proposed methodologies are very useful in terms of battery recycling.

[0032] The invention makes it possible to guarantee the safety of the battery by adjusting as closely as possible the capacity health status and the resistance health status on which the available power limits and the overcurrent diagnosis depend.

[0033] The invention proposes, in the event of unavailability of means for complete electrical tests: a simple rewriting of the quantities of health status in capacity, health status in resistance, discharged energy, charged energy, and the usage data matrices in parking and driving which are very useful for the reuse of the battery, by adjusting the safety limits as best as possible.

[0034] Regarding the state of charge, sufficient relaxation can be required and the battery can be forced to start. The state of charge is determined from the voltage measurements. For example, a matching curve exists and is the heart of the algorithms of battery management systems, namely the curve of the state of charge as a function of the open circuit voltage of the cells.

[0035] This method works for batteries using NMC technology (for “nickel-manganese-cobalt positive electrode”) where the above-mentioned curve does not show plateaus or significant hysteresis between charge and discharge.

[0036] Concerning batteries in LFP technology (for "lithium iron phosphate positive electrode"), or other, which have these aforementioned drawbacks, it is rather necessary: ​​- either to carry out a complete charge to learn a correct state of charge of the battery pack at 100%; - either perform a complete discharge at constant current with a stopping criterion based on a minimum cell voltage equal to the cut-off voltage to learn a correct state of charge of the battery pack at 0%.

[0037] Regarding the capacity health status, a sequence with a deep charge or discharge preceded and followed by a pause at zero current may be required, respecting sufficient relaxation at the beginning and end of the charge or discharge. This is done with stopping criteria based on maximum cell voltage and minimum cell voltage

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[0047] cells. With a single electrical quantity variation Q for all cells, the state of charge variation A SOC / comes from the conversion of all the voltages measured during relaxations. With this method we obtain the capacity Capa, of all the cells: CaPai = This capacity can be converted into a state of health capacity SOHCj by dividing the estimated capacity Capa^ by a reference value Cap&^ which is well known in the new state of the battery: SOHCf = Capüf Caparef For LFP technology batteries, a discharge can be carried out followed by a complete charge stopped on voltage criteria; with an evaluation at the end of the charged energy Etot: hangs Etot = Jf0 Pbatt dt with PBatter = Upack*Ipack Reduced to its new value, this measurement guides towards the state of health in energy which can be approximated to that of the state of health in SOHC capacity; SOHC=p— Energy_refBQL If charging or discharging facilities are not available for maintenance / after-sales service, the solution is as follows: Use the on-board battery chemistry durability model combined with an approximate temperature indication to estimate degradation in terms of capacity loss. This simplified durability model can be viewed as a three-dimensional table of capacity health status as a function of temperature, mileage, and age (in days). Mileage and duration information since the battery was put into production can be retrieved (approximate with user feedback and the latest revisions or via online information, for example in the cloud or via a so-called OTA (Over The Air) system). Indeed, mileage can be considered as the image of the energy discharged from the battery and therefore the number of cycles, and subsequently the aging of the battery. The mileage can be adjusted with an energy consumption of an electric vehicle (e.g. 12.5kWh / 100km) which is well known to car manufacturers. Regarding the state of health in resistance, a correct assessment of the increase in Internal resistance helps to avoid overestimating the power available for discharge (which can prematurely degrade battery durability) or overestimating the power available for regeneration, which can lead to a deposit of metallic lithium (or “Lithium plating” in English).

[0048] Thus, two alternatives are considered, one by electrical tests, the other by an equivalence curve.

[0049] If the maintenance / after-sales service has the means to carry out discharge pulses, then the equivalent of a standard test is carried out to measure the resistance: For example, a constant current pulse 1 is applied at 50% state of charge at 25°C for a duration of 10s or 30s and with the measurements of cell voltage variations “i” noted AV_i, the current resistance DCR_i is quantified with the following equation: DCR_i = ^

[0050] Subsequently, it is sufficient to bring this back to a state of health in resistance on the scale of the SOHR_i cell, by dividing by the nine reference resistance DCRb (generally available on the battery instructions): SOHR_i = ^

[0051] The choice of the state of charge, temperature, current and target duration could precisely be guided by the availability of the reference resistance information at new.

[0052] If only one health state in resistance at the pack scale needs to be entered, it can be estimated by the maximum of the health states in resistance at the cell scale.

[0053] A second alternative in the event of unavailability of charging / discharging means is to use a chart of the evolution of the state of health in resistance as a function of the state of health in capacity which will be guided by thermal information. The temperature is still important here to adapt the law of variation of the state of health in resistance with aging.

[0054] For the record, at a minimum the average living temperature could be adapted according to climate information and meteorological data from the location of the car's circulation.

[0055] Note that the effect of driving, including charge / discharge currents, can influence the increase in resistance from one user to another. Thus, it is preferable to consider an average user for the abacus, and an additional safety margin on the value of the state of health in resistance ranging from 10% to 15% depending on the continuation of the use of the battery (15% for a recovery of a battery or 10% for a reuse of a battery with less power required).

[0056] Health status information in capacity or resistance, which does not deviate too much from reality, may be necessary to avoid security risks by adjusting cor rectly power limitations and overcurrent diagnostic limits which are dependent on battery age.

[0057] Regarding the vehicle usage history, the battery management system provides information on the usage history of the battery life. In the event of a loss of non-volatile memory, this information will no longer be available.

[0058] The battery usage history contains matrices divided into charge states and temperatures for a number of times spent at such or such operating point; as well as the charged and discharged energies in kilowatt hours.

[0059] We distinguish between matrices for the calendar requirement called parking matrix, and matrices for the cycling requirement called “cycling”.

[0060] For the parking and driving matrices, the invention proposes a filling with an offline available durability model considering an average user aiming for the same capacity health target.

[0061] The sustainability model is accessible to sustainability teams of automotive manufacturers and battery chemistry suppliers.

[0062] For discharged and charged energies, mileage and consumption information will be recommended. The energy discharged from new can be determined by multiplying the energy consumption per distance (for example in kWh / km), by the distance traveled (for example in km).

[0063] The energy charged from new can be determined by dividing the discharged energy by the energy efficiency of the battery (for example an efficiency of 0.99 for lithium batteries).

[0064] The invention further relates to the corresponding backup and restoration program.

[0065] The invention makes it possible to avoid replacing a battery of an electric vehicle due to a hardware defect in the battery management system and to discard other functional hardware.

[0066] The invention makes it possible to prepare the ground for recycling even for a case of recovery of the battery with another battery management system hardware. For example, the methodology could be very useful for the classification of batteries.

Claims

Claims

1. Method for backing up and restoring a battery management system of a battery which comprises a non-volatile memory, the method comprising the following steps: - a determination step (El) in which at least one electrical test is carried out on the battery and / or at least one model is used, to determine driving data; - a backup step (E2) in which vehicle usage data, as well as the driving data, are saved in a backup memory; - in the event of a fault or recycling of the non-volatile memory (H), a restoration step (E3) in which the vehicle usage data, as well as the driving data, are restored from the backup memory to the non-volatile memory.

2. Backup and restore method according to claim 1, wherein the battery has a state of charge, a capacity health state, a resistance health state, and the battery management system comprises values ​​of states of charge and temperature, characterized in that the driving data comprises at least one of the state of charge, the capacity health state, the resistance health state, and the usage data comprises charged energies and discharged energies and / or matrices of states of charge and temperatures at different operating points.

3. Backup and restoration method according to claim 2, in which the battery management system comprises values ​​of energy consumption per distance, distances traveled, and energy efficiency of the battery, characterized in that the discharged energies are determined from the energy consumption per distance and the distances traveled; and the charged energies are determined from the discharged energies and the energy efficiency of the battery.

4. A backup and restore method according to any one of claims 1 to 3, wherein the battery has a state of charge, characterized in that the driving data comprises the state of charge, and said electrical test comprises a relaxation and a restart of the battery, then an estimation of the state of charge from voltage measurements; or a complete charge or discharge and a check the charge status.

5. A backup and restore method according to any one of claims 1 to 4, wherein the battery has a capacity health status at ambient temperature, characterized in that the driving data comprises the capacity health status, and said electrical test comprises a partial charge or discharge preceded and followed by a relaxation to determine the capacity and the capacity health status; or a discharge followed by a full charge to determine the charged energy and deduce the capacity health status therefrom.

6. Backup and restore method according to any one of claims 1 to 5, characterized in that the driving data comprises the capacity health status and said model comprises a capacity health status model as a function of chemical parameters of the battery and the ambient temperature.

7. A backup and restore method according to any one of claims 1 to 6, wherein the battery has a resistance health status, characterized in that the driving data comprises the resistance health status, and said electrical test comprises an application of current pulsation and a measurement of battery cell voltage variation to determine the current resistance, and the resistance health status.

8. Backup and restoration method according to any one of claims 1 to 7, characterized in that the model comprises an equivalence curve of the state of health in resistance compared to the state of health in capacity and temperature.

9. A computer program comprising program code instructions for performing the steps of the backup and restore method according to any one of claims 1 to 8, when said program is running on a computer.

10. A motor vehicle comprising a battery and a battery management system of the battery, which comprises a non-volatile memory, characterized in that it further comprises a control unit implementing a backup and restoration method according to any one of claims 1 to 8.

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