Vehicle comprising a rechargeable battery and means for determining the maximum permissible power for the battery during a charging phase

Abstract

This power supply system for a rechargeable electric storage battery for an electric or hybrid motor vehicle includes means for determining the maximum permissible power for the battery (BATPIN(t)) as a function of a first maximum power (BATPINPOWERMAP(t)) corresponding to a regeneration phase and a second maximum power (BATPCHGPOWERMAP(t)) corresponding to a battery charging phase. Figure for the abstract: Fig 3A

Description

Title of the invention: Vehicle comprising a rechargeable battery and means for determining the maximum permissible power for the battery during a charging phase technical field

[0001] The invention relates to electric battery management systems, and in particular to on-board electric battery management systems intended to power an electric or hybrid motor vehicle. Previous techniques

[0002] Motor vehicle batteries can either be recharged at electrical charging stations when the vehicle is stationary, or recharged by recovering, through the electric motor, some of the vehicle's kinetic energy when it decelerates. Such energy recovery is commonly called regenerative braking.

[0003] Batteries can deteriorate or age and thus reduce their capacity to store energy. This aging depends on the conditions under which the batteries are used when a vehicle is in operation.

[0004] In order to preserve the integrity of the battery, it is proposed to limit the power of its charge.

[0005] This limitation is all the more important when the state of charge of the battery is high.

[0006] The charging capacity gradually drops towards zero as it approaches full battery charge.

[0007] Similarly, when the battery temperature is typically below 0°C.

[0008] Moreover, when the charging power exceeds a predetermined threshold depending at least on the chemical nature and dimensions of the battery cells, the latter loses its integrity.

[0009] Furthermore, when the battery is lithium-ion, a deposit of lithium layers has been observed on its electrodes during excessively high charging power. The battery's charging capacity is significantly reduced to limit this phenomenon.

[0010] Consequently, manufacturers of such batteries provide a map indicating the maximum permissible power for the battery as a function of its temperature and state of charge during a charging phase using a power supply terminal.

[0011] The battery is also rechargeable during a driving phase, during a braking phase or when lifting off the foot, known as the regeneration phase.

[0012] The maximum permissible power is higher here but can only be applied for a shorter period of time, on the order of ten seconds, in order not to damage the battery.

[0013] The manufacturers then developed a second map of the maximum permissible power for the battery as a function of its temperature and state of charge during a regeneration phase.

[0014] However, if the regeneration phase proves to be longer than the duration defined by said second mapping, the battery is likely to be damaged.

[0015] A so-called modulation strategy, described in patent bearing the reference FR2994027, is then implemented by a battery management system BMS (for "Battery Management System" in English) in order to progressively limit the amount of power supplied to the battery.

[0016] Such a strategy consists of a limitation of the maximum permissible power, at each instant of the regeneration phase, which depends both on a value read in the first map of maximum permissible power values ​​during the charging phase and on a value read in the second map of maximum permissible power values ​​during the regeneration phase.

[0017] In other words, it involves gradually switching from a limitation of the maximum permissible power value from the second map to a limitation of the maximum permissible power value read in the first map.

[0018] However, this strategy is only used during the regeneration phase but in no case during the charging phase.

[0019] The battery is then deprived of a high charging power, which, when permitted for a predefined period of time, does not damage the battery. The battery's charging potential during the charging phase is therefore only partially utilized.

[0020] The aim of the invention is therefore to improve the electrical power supply systems of the motor vehicle battery during the charging phases. Description of the invention

[0021] In view of the foregoing, the invention relates to a power supply system for a rechargeable electric storage battery for an electric or hybrid motor vehicle, the battery being rechargeable during regeneration phases and during charging phases, the system comprising means for determining a maximum permissible power for the battery.

[0022] The means for determining the maximum permissible power for the battery include a first map enabling the reading of a first maximum power from the temperature and state of charge of the battery, a second map enabling the reading of a second maximum power from the temperature and state of charge of the battery, the first map including values ​​of first maximum power corresponding to a regeneration phase and the second map including values ​​of second maximum power corresponding to a charging phase of the battery, and means for calculating said maximum permissible power for the battery during the charging phase as a function of the first maximum power and the second maximum power.

[0023] In other words, the computing means are configured to exploit the first mapping and the second mapping to implement the modulation strategy during the battery charging phase.

[0024] The modulation strategy then makes it possible to gradually increase the charging power until reaching a first maximum permissible charging power value from the first mapping and corresponding to the state of charge and the temperature of the battery at time t.

[0025] Thus, at equivalent temperature and state of charge, the first maximum permissible charging power value is greater than a second corresponding maximum charging power value which comes from the second mapping.

[0026] The evolution of the maximum permissible charging power will then substantially follow the values ​​from the first mapping for a predetermined period before gradually decreasing to reach a second maximum power value from the second mapping.

[0027] Finally, as soon as the maximum permissible power has reached the second value, the maximum permissible power will substantially follow the maximum power values ​​indicated in the second map as the load increases.

[0028] Advantageously, the calculation means are configured to calculate the sum of the first power with a first coefficient a(t) between 0 and 1 and the second power with a second coefficient equal to 1- a(t).

[0029] The first coefficient a(t) is chosen so as to obtain a chosen limitation between the first maximum power (if it is equal to one), the second maximum power (if it is equal to 0) and a weighting of these two powers if it is between 0 and 1.

[0030] Preferably, the calculation means are configured to adjust the value of the first power so as to be less than or equal to a predetermined threshold value when the first coefficient a(t) is equal to 1.

[0031] Battery durability is affected when there is a significant difference between the first charging power and the second charging power at equivalent temperature and state of charge.

[0032] It is then proposed to maintain the value of the maximum permissible load power less than or equal to said predetermined threshold value.

[0033] Preferably, the computing means are configured to maintain the first coefficient a(t) at 1 for a predetermined duration.

[0034] In other words, it is a matter of calculating said maximum permissible power for the battery only as a function of the first maximum power during said predetermined duration.

[0035] Advantageously, the battery is composed of one or more cells, the system comprising means for measuring the voltage across the terminals of a cell and means for limiting the maximum permissible power for the battery providing a third maximum power value calculated as a function of a maximum voltage value and the measured cell voltage.

[0036] Calculating a third maximum power value based on these two parameters helps to protect the battery.

[0037] The invention further relates to an electric or hybrid motor vehicle comprising a rechargeable electric storage battery, a braking system enabling energy recovery, the battery being rechargeable during regeneration phases and during charging phases, and a power supply system for said battery as defined above.

[0038] The invention also relates to a method for regulating the charge of a rechargeable electric storage battery of an electric or hybrid motor vehicle comprising a braking system allowing energy recovery, the battery being rechargeable during regeneration phases and during charging phases.

[0039] The method includes a step of determining a first maximum power corresponding to a regeneration phase, a step of determining a second maximum power corresponding to a battery charging phase, and a step of calculating the maximum permissible power for the battery during the charging phase as a function of the first maximum power and the second maximum power.

[0040] Advantageously, the calculation of said maximum permissible power includes a summation of the first power affected by a first coefficient a(t) between 0 and 1 and of the second power affected by a second coefficient equal to 1 -a(t).

[0041] Preferably, the first power value is adjusted so as to be less than or equal to a predetermined threshold value when the first coefficient a(t) is equal to 1.

[0042] Preferably, the first coefficient a(t) is maintained at 1 for a predetermined duration.

[0043] Advantageously, when the battery is composed of one or more cells, the voltage across the terminals of a cell is measured and the maximum permissible power for the battery is limited from a third maximum power value calculated as a function of a maximum voltage value and the measured cell voltage. Brief description of the drawings

[0044] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example, and made with reference to the indexed drawings in which:

[0045] [Fig. 1] illustrates a first map and a second map including maximum power values ​​respectively during a regeneration phase and during a charging phase of a battery of a motor vehicle according to the prior art.

[0046] [Fig.2] schematically represents a battery power supply system 2 according to an embodiment of the invention and,

[0047] [Fig.3A] and

[0048] [Fig.3B] represent a first graph and a second graph of the evolution of the maximum permissible power for the battery during the charging phase according to two modes of implementation of the invention.

[0049] Detailed description of the embodiments of Fin vention

[0050] For a motor vehicle battery comprising one or more individual cells, the development of maps of maximum permissible power can be implemented by means of maps of the internal resistance of a battery cell for example.

[0051] These maps can be obtained by prior calibration steps and allow this resistance to be read as a function of the battery's state of charge and its temperature.

[0052] The state of charge of the battery depends directly on the open circuit voltages of OCV cells (for "Open Circuit Voltage" in English) and can therefore be measured by means of voltage sensors.

[0053] The maximum permissible voltage VLimitepiN for a cell carrying a current during a regeneration phase can also be obtained by calibration with

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[0071] energy recovery, and the maximum voltage allowed vLimitepeuG by a cell through which a current flows during a charging phase. All of this data allows us to determine the maximum permissible power for the battery during the charging phase and during the regeneration phase using equation 1: TfMAXPIN _ VLhnitePiN-ocv BAT DCReli LimitePIN EQ. 1 ■pMAXPCHG _ V LinMePCHG-°CV *BAT ~ DCRceI] v UmitePCHG With : pMAXPIN ■ First maximum power allowed during the regeneration phase, and : Second maximum power allowed during the charging phase. We can then form, as illustrated in Figure 1, a first Cl map including initial maximum power values ​​as a function of The state of charge of the battery (SOC) expressed as a percentage. Figure 1 further illustrates a second C2 map including second maximum power values ​​pMAXPCHG as a function of the state of charge of the SOC battery. Thus, at each instant (denoted t), we obtain a maximum permissible power for the battery with equation 2: BAT P IM ( t) = (x( t ) * BAT PIM pç)wermap^ O + ( l-ot(t ) )* BATPCH Growermap ( t ) EQ.2 With : BATPIN(t): Maximum permissible power for the battery at time t, BATPINpowERMAp(t): First maximum permissible power in regeneration phase at time t obtained on the first map Cl; BATPCHGpowERMAp(t): Second maximum permissible power in charging phase at time t obtained on the second map C2; a(t): First coefficient between zero and one. Thus, if the first coefficient a(t) is equal to 1, the maximum permissible power BATPIN(t) for the battery is the first maximum permissible power in the regeneration phase BATPINpowermap(I), which is a high value. Conversely, if the first coefficient a(t) is equal to zero, the maximum permissible power BATPIN(t) for the battery is the second maximum permissible power during charging phase BATPCHGp0wermap(1), which is a low value and can be applied for a long time without damaging the battery.

[0072] In [Fig.2], a power supply system 2 is shown comprising means for determining the maximum permissible power BATPIN(t) during the battery charging phase.

[0073] Such means for determining the maximum permissible power BATPIN(t) are configured to implement the calculation of equation 2.

[0074] By using on the one hand the first map Cl comprising the first maximum permissible power values ​​BATPINp0WERMAp(t) corresponding to the regeneration phases and on the other hand the second map C2 comprising the second maximum permissible power values ​​BATPCHGp0wermap(1) corresponding to the charging phases, calculation or modulation means 5 can be used to provide the value of the maximum permissible charging power BATPIN(t) for the battery.

[0075] Thus, as illustrated in [Fig.3A], the first curve VI in solid line represents the evolution of the maximum permissible charging power BATPIN(t), expressed in Watts, as a function of the state of charge SOC of the battery or the voltage for a given temperature.

[0076] The modulation strategy here allows the maximum permissible charging power BATPIN(t) to be increased progressively until a first charging power value PI is reached from the first mapping Cl and corresponding to the state of charge SOC at time t.

[0077] Thus, at equivalent temperature and state of charge, the first maximum permissible charging power value PI is greater than a corresponding second maximum permissible charging power value P2 from the second map C2.

[0078] The evolution of the maximum permissible charging power BATPIN(t) will then substantially follow the values ​​BATPINP0WERMAP(t) from the first mapping Cl for a first predetermined duration DI before gradually decreasing to reach a third maximum power value P3 from the second mapping C2.

[0079] By way of example, the first predetermined duration DI is between 10 seconds and a few minutes.

[0080] Finally, as soon as the maximum permissible power BATPIN(t) has reached the third value P3, this will substantially follow the second maximum power values ​​BATPCHGP0WERMap(t) indicated in the second map C2 as the battery is charged.

[0081] Furthermore, it should be noted that the battery's durability can be impaired when there is a significant difference between the first charging power BATPINpowermap(I) and the second charging power BATPCHGp0WERMap(t) at equivalent temperature and state of charge SOC.

[0082] By way of example, the difference may be on the order of several tens of kilowatts (kW).

[0083] The computing means 5 can then be configured to adjust the value of the first maximum power BATPINp0WERMap(t) so as to be less than or equal to a predetermined threshold value P4 when the coefficient a(t) is equal to 1.

[0084] In this case, it is a second curve V2 in solid line which represents the evolution of the maximum permissible charging power BATPIN(t) as a function of the state of charge SOC of the battery.

[0085] It should be noted that the modulation strategy can be applied to all temperature values.

[0086] Alternatively, as illustrated in [Fig.3B], the computing means 5 are configured to maintain the coefficient a(t) at 1 for a second predetermined duration D2, between a few seconds and a few minutes, to protect the battery against a high variability of the charging power BATPIN(t) during the charging phase.

[0087] Moreover, the invention is not limited to these embodiments and implementations but encompasses all variants thereof.

[0088] The invention relates for example to applications equipped with batteries whose ratio between current and charge capacity ("C-rate") is greater than 1.

Claims

Demands

1. Power supply system (2) for a rechargeable electric storage battery for an electric or hybrid motor vehicle, the battery being rechargeable during regeneration phases and during charging phases, the system comprising means for determining a maximum permissible power for the battery (BATPIN(t)), the means for determining the maximum permissible power for the battery comprising a first map (C1) for reading a first maximum power (BATPINpowERMAp(t)) from the temperature and state of charge of the battery (SOC), a second map (C2) for reading a second maximum power (BATPCHGPowermap(1)) from the temperature and state of charge of the battery (SOC),the first map (C1) comprising first maximum power values ​​(BATPINpowermap(I)) corresponding to a regeneration phase and the second map (C2) comprising second maximum power values ​​(BATPCHGpowermap(I)) corresponding to a battery charging phase, and means for calculating said maximum permissible power (BATPIN(t)) for the battery during the charging phase as a function of the first maximum power (BATPINpowermap(I)) and the second maximum power (BATPCHGpowermap(I)), at equivalent temperature and state of charge, the first maximum permissible charging power value (BATPINpowermap(I)) being greater than the second maximum permissible charging power value (BATPCHGpowermap(t)),in which the computing means (5) are configured to calculate the sum of the first power (BATPINpowERMAp(t)) with a first coefficient a(t) between 0 and 1 and the second power (BATPCHGPowermap(1)) with a second coefficient equal to 1- a(t), characterized in that the computing means (5) are configured to maintain the first coefficient a(t) at 1 for a predetermined duration (D2).

2. Power supply system (2) according to claim 1, wherein the computing means (5) are configured to adjust the value of the first power (BATPINPowermap(1)) so as to be less than or equal to a predetermined threshold value (P4) when the first coefficient a(t) is equal to 1.

3. Power supply system (2) according to claim 1 or 2, wherein the battery is composed of one or more cells, the system (2) comprising means for measuring the voltage across a cell and means for limiting the maximum permissible power for the battery providing a third maximum power value calculated as a function of a maximum voltage value and the measured cell voltage.

4. Electric or hybrid powered motor vehicle comprising a rechargeable electric storage battery, a braking system enabling energy recovery, the battery being rechargeable during regeneration phases and during charging phases, and a power supply system (2) for said battery according to any one of claims 1 to 3.

5. A method for regulating the charge of a rechargeable electric storage battery of an electric or hybrid motor vehicle comprising a braking system enabling energy recovery, the battery being rechargeable during regeneration phases and during charging phases, the method comprising: - a step of determining a first maximum power (BATPINpowERMAp(t)) corresponding to a regeneration phase read in a first map (Cl) allowing the reading of a first maximum power (BATPINp0WERMAp(t)) from the temperature and state of charge of the battery (SOC) and comprising first maximum power values ​​(BATPINpowermap(I)) corresponding to a regeneration phase,- a step of determining a second maximum power (BATPCHGpowermap^)) corresponding to a battery charging phase read in a second map (C2) allowing the reading of a second maximum power (BATPCHGpowermap(I)) from the temperature and state of charge of the battery (SOC) and including values ​​of second maximum power (BATPCHGpowermapW) corresponding to a battery charging phase, and - a step of calculating the maximum permissible power (BATPIN(t)) for the battery during the charging phase as a function of the first maximum power (BATPINpowermap(I)) and the second maximum power (BATPCHGpowermap^)), in which, at equivalent temperature and state of charge, the first maximum permissible charging power value (BATPINpowERMAp(t)) is greater than the second maximum permissible charging power value (BATPCHGp0WERMAp(t)), in which the calculation of said maximum permissible power (BATPIN(t)) comprises a sum of the first power (BATPINpowERMAp(t)) affected by a first coefficient a(t) between 0 and 1 and the second power (BATPCHGp0WERMAp(t)) affected by a second coefficient equal to 1 - a(t), characterized in that the first coefficient a(t) is maintained at 1 for a predetermined duration (D2).

6. A method according to claim 5, wherein the first power value (BATPINp0WERMAp(t)) is adjusted so as to be less than or equal to a predetermined threshold value (P4) when the first coefficient a(t) is equal to 1.

7. Method according to claim 5 or 6, wherein, when the battery is composed of one or more cells, the voltage across the terminals of a cell is measured and the maximum permissible power for the battery is limited from a third maximum power value calculated as a function of a maximum voltage value and the measured cell voltage.

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