PROCEDURE FOR MANAGING AN ELECTRIC VEHICLE BATTERY CHARGING

Abstract

The invention relates to a method for managing a charging sequence of a battery pack in an electric vehicle, comprising an on-board computer connected to an external temperature sensor and a battery management computer, characterized in that the method comprises: - a step of measuring an external temperature and making the external temperature information available via the on-board computer, - a step of determining a limit charge level threshold (SLIM) based on the external temperature information, by the battery management computer, - a step of evaluating a current charge level (SOCC) of the battery pack by the battery management computer, - a step of interrupting an ongoing charging sequence if the current charge level exceeds the limit charge level threshold. Figure 2

Description

Title of the invention: METHOD FOR MANAGING THE RECHARGE OF AN ELECTRIC VEHICLE BATTERY

[0001] The invention relates to a method for managing a recharging sequence of a battery of an electric vehicle. Particular attention is paid to circumstances of high external temperature, for example when the vehicle is used in tropical or equatorial or similar geographical areas, or even in temperate zones during periods of heatwave.

[0002] The battery of an electric vehicle comprises electrochemical cells grouped in a unit called in the trade 'battery pack'.

[0003] An electric vehicle includes a cooling system configured to cool the battery pack so that said battery pack remains within an optimal temperature range for its efficient use and for optimizing its lifespan.

[0004] When the vehicle is in use or being recharged, the cooling system is in operation as needed. However, in certain configurations where the vehicle is parked, the cooling system is not in operation, it is in fact not powered and cannot operate.

[0005] Too high a temperature or too low a temperature are sources of premature aging of the electrochemical cells of the battery pack.

[0006] The present invention relates to circumstances where the vehicle is parked in a non-use configuration. More specifically, the focus is on managing the end of a charging sequence in conditions of high ambient temperature currently in progress or expected in the short term.

[0007] Several charging modes can be used depending on the capacity of the charging terminal to deliver electrical power and the capacity of the vehicle's electrical system to admit a certain charging current to recharge the battery pack.

[0008] Charging can be carried out in a domestic context using a standard power outlet. It is also possible to use a more powerful specific outlet, often called in practice a 'wallbox'. In addition, it is possible to use public or semi-public charging stations for fast charging, in which the flow of electrical energy is several tens of kilowatts.

[0009] The inventors were interested in the question of preventing premature aging of the battery pack when the vehicle is used in tropical or equatorial or similar geographical areas, or even in temperate zones during periods of heatwave.

[0010] The inventors noticed that the phenomenon of aging of electrochemical cells not electrically stressed was proportional not only to a high surrounding temperature, but also to the level of electrical energy charge that they contain.

[0011] To this end, the present invention proposes a method for managing a recharging sequence of a battery pack of an electric vehicle, in a vehicle comprising said battery pack, at least one on-board computer connected to an outside temperature sensor and a battery management computer (this computer is called in the jargon of the trade BMS from the English Battery Management System), characterized in that the method comprises: - a step of measuring an outside temperature, and making the outside temperature information available via the on-board computer, - a step of determining a limit charge level threshold based at least on the outside temperature information, by the battery management computer, - a step of evaluating a current charge level of the battery pack by the battery management computer, - a step of interrupting a current charging sequence if the current charge level exceeds the limit charge level threshold.

[0012] Thanks to the provisions promoted above, if the outside temperature is too high, recharging is interrupted before the charge level has reached the total capacity of the battery pack.

[0013] This avoids having a fully charged battery exposed for a long time to temperatures beyond the temperatures normally permissible for an optimal lifespan. In other words, the recharge is capped at a level lower than that which could be achieved at a lower surrounding temperature. This makes it possible to increase the healthy lifespan of the battery pack, and / or to reduce the effects of aging linked to exposure to high temperatures.

[0014] It is noted that the above logic is independent of the temperature measured at the electrochemical cells of the battery pack during recharging. It is indeed the temperature of the external environment which is the decision criterion. However, the anti-runaway cell monitoring safety devices remain active and recharging can be interrupted on a criterion other than the external temperature criterion in the case where one of the temperature sensors arranged in the battery pack reveals a temperature which is too high.

[0015] According to one embodiment, the limit charge level threshold is expressed as a percentage of a total capacity usable by the user. Thus, in cir constants where the total user capacity decreases according to the aging of the battery pack, the threshold in question can change in value (in KWh) while it remains constant in percentage.

[0016] It is noted that if the limit charge level threshold is at 100%, then there is no charge interruption action and charging continues until the battery is fully recharged as in the nominal case at moderate temperature.

[0017] According to one embodiment, the limit charge level threshold is between 60% and 85% of a total useful capacity if the outside temperature information is higher than a temperature switching threshold between 35°C and 45°C. The values ​​in question can be adjusted after tests and can differ from one type of vehicle to another, or from one technical platform to another.

[0018] According to one embodiment, the limit charge level threshold is established as a function of the outside temperature, according to a map resulting from validation tests. It is thus possible to adjust the charging capping strategy as necessary, while protecting the battery pack from aging while limiting the adverse impact on the use of the vehicle.

[0019] According to one embodiment, the temperature information is supplemented by auxiliary local temperature information available through an internet connection, via a connected telematics system of the vehicle or via a multifunction mobile telephone of the user coupled locally to an electronic system of the vehicle.

[0020] The auxiliary temperature information supplements the information delivered by the sensor present on the vehicle, or replaces the information delivered by the sensor present on the vehicle if this information is not available or clearly erroneous.

[0021] According to a particular example, the battery management calculator can take the maximum value of the two aforementioned temperature values.

[0022] According to one embodiment, the limit charge level threshold can be further adjusted as a function of short-term local temperature forecasts. It is thus possible to take the decision to limit the charging cap, not only as a function of the temperature recorded at time t, but also thanks to the temperature forecast in the hours following time t.

[0023] According to one embodiment, the current charge level is evaluated during recharging at least by integrating over time a value of electric current which enters the battery pack and with reference to voltage measurements made at rest.

[0024] The current charge level can thus be calculated precisely, for example using a current sensor, so that the estimated value is as faithful as possible to reality and so that the interruption of the recharge sequence occurs at the expected charge level.

[0025] According to one embodiment, a step of providing information to the user is also provided. Whereby, if the user realizes that the autonomy or the relative level of recharge is lower than that which was expected, he can know the reason and avoid interpreting this as an anomaly.

[0026] The invention further relates to a vehicle comprising a battery pack, at least one on-board computer connected to an outside temperature sensor and a battery management computer, characterized in that the on-board computer and the battery management computer are configured to implement the method as described previously.

[0027] The invention further relates to a system comprising a vehicle as described previously implementing the method as described previously, and a remote server configured to deliver geolocated weather information as well as short-term weather forecasts.

[0028] The invention will be further detailed by the description of non-limiting embodiments, and on the basis of the appended figures illustrating variants of the invention, in which: [Fig.l] is a schematic representation of an exemplary electric vehicle with an electrical energy storage system, in which the present invention is implemented; [Fig.2] schematically shows a diagram of the battery pack charge levels and an example of a timing diagram; [Fig.3] illustrates a simple example of relationships between outside temperature and a limit load level threshold.

[0029] In the various figures, the same references designate identical or similar elements. For reasons of clarity of the description, certain elements are not necessarily represented to scale.

[0030] A general diagram of an electric traction battery system in an electric vehicle 7 is now described with reference to [Fig.l].

[0031] The battery assembly, also called battery pack, referenced 2, comprises a plurality of battery modules, each module comprising electrochemical cells as known per se.

[0032] Regarding the quantity of energy stored in the battery pack, in practice we are talking about several tens of kWh. A 100% electric vehicle battery has an energy storage capacity typically between 40 kWh and 100 kWh, depending on the target autonomy, the weight and the consumption of said vehicle.

[0033] The most common traction batteries on electric vehicles are batteries based on Lithium-Ion type electrochemistry. According to one configuration, a battery pack is generally made up of several modules connected together in a series configuration, each module itself comprising a plurality of unit electrochemical cells, arranged in series and / or in parallel. According to another configuration, a battery pack consists of a plurality of unit electrochemical cells, all arranged at the same hierarchical level of integration, without grouping into sub-assemblies or modules.

[0034] The vehicle comprises, in addition to the battery pack 2, at least one on-board computer 4, for example a supervisor computer or a passenger compartment multifunction computer, and a battery management computer 1 (this computer is called in the jargon of the BMS profession, from the English Battery Management System).

[0035] The on-board computer 4 is connected to an outside temperature sensor 74. For example, the outside temperature sensor 74 is arranged in an exterior rearview mirror 75. Other locations are also possible for housing the outside temperature sensor.

[0036] To recharge electric vehicles, it is necessary to use an electric charging cable 32 intended to connect on the one hand a charging base 72 on the vehicle side and on the other hand a power supply socket 62 on the opposite side, namely the station side or the residential electrical socket, generically referenced 6.

[0037] The charging station can deliver electrical energy in alternating current or direct current.

[0038] The vehicle 7 comprises a cooling system configured to cool the battery pack so that said battery pack remains within an optimal temperature range for its efficient use and for optimizing its lifespan. This cooling system comprises, in the illustrated example, a calorie collection plate 76 located under the battery pack 2.

[0039] This cooling system maintains the electrochemical cells of the battery in an optimal temperature range, say between 15°C and 45°C without these values ​​being limiting.

[0040] The system implementing the invention also comprises an on-board charger 3, often called in practice 'OBC' from its Anglo-Saxon name On Board Charger. The on-board charger 3 communicates with the charging station 6 to jointly define the most appropriate charging mode with regard to the resources on each side in terms of electrical power, capacity to be delivered and capacity to be admitted.

[0041] As known per se, several charging modes are defined in the IEC 62196 and ISO 15-118 standards, for example type 2 mode, type 3 mode, and type 4 mode known per se and therefore not detailed here.

[0042] The on-board charger 3 comprises an alternating current to direct current (AC / DC) converter and a direct current DC / DC voltage converter. The output of the voltage converter AC / DC is connected to the positive and negative terminals of the battery pack 1.

[0043] The method promoted according to the present invention comprises a step of acquiring the outside temperature prevailing in the environment around the vehicle.

[0044] An outside temperature TPEXT is measured by means of a temperature sensor, which may be, for example, a negative coefficient resistance probe (NCT), connected to the on-board computer. Alternatively, a mechatronic unit may be used which contains the sensor and an electronic circuit which can transmit digital information presenting the measured temperature on a multiplexed bus 14 to other on-board computers.

[0045] The outside temperature information is made available from the on-board computer 4. One of the calculations using this information is, in the context of the present invention, the battery management computer 1 (BMS).

[0046] The on-board computer 4 may be an electromotive group supervisor, or may be a passenger compartment multifunction computer, an instrument cluster or another on-board computer depending on the electrical and electronic architecture of the vehicle of interest.

[0047] The method comprises a step of determining a SLIM limit charge level threshold as a function of the outside temperature information, by the battery management computer.

[0048] Here it should be noted that we can define the total theoretical capacity of the battery pack, i.e. corresponding to 100% of the electrical energy which can be contained therein.

[0049] In practice, the concept of total capacity usable by the user is also used.

[0050] As illustrated in [Fig.2], the total usable capacity is somewhat smaller than the theoretical total capacity because the lower fringe 52 is never consumed in practice to avoid damaging the electrodes and the electrolyte. Similarly, the upper fringe 51 is also not used in practice because recharging the last percent or the last 2 percent may require applying an excess voltage which can be harmful and unfavorable if we consider the life of the battery pack.

[0051] In practice, the SLIM limit charge level threshold is expressed as a percentage of the total capacity usable by the user.

[0052] According to an exemplary embodiment, the SLIM limit charge level threshold is between 60% and 85% of a total useful capacity if the outside temperature information is greater than a temperature switching threshold between 35°C and 45°C.

[0053] The load limit and temperature switching thresholds can of course take other values.

[0054] According to a particular embodiment, the SLIM limit load level threshold is established as a function of the outside temperature, according to a map resulting from tests validation, illustrated in solid line in [Fig.3]. Thus, curve 56 shows that SLIM decreases from 100% at TPEXT 35°C to 60% at TPEXT 45°C.

[0055] According to another embodiment, the SLIM limit charge level threshold switches abruptly from 100% to 60% at TPEXT = 40°C. This is illustrated by the dotted line curve 55 in [Fig.3].

[0056] Of course, the values ​​used as well as the shape of the mapping curve may depend on the type of battery pack, the nuance of the electrochemical configuration of the cells.

[0057] The method also comprises a step of evaluating a current charge level SOCC of the battery pack by the battery management computer 1.

[0058] The calculation of the current charge level SOCC can be done in different ways, known per se. For example, the current charge level SOCC can be calculated according to the teachings of document US 11662387.

[0059] According to one example, during recharging, the current charge level SOCC is evaluated by integrating over time the electric current entering the battery pack and with reference to previous voltage measurements made at rest.

[0060] The method comprises a step of interrupting a current recharging sequence if the current charge level exceeds the limit charge level threshold.

[0061] When the vehicle is being recharged, the battery management computer compares the current charge level SOCC with the limit charge level SLIM which gradually increases as shown in curve 53.

[0062] With reference to [Fig.2], at the instant denoted ts, the current charge level SOCC reaches the limit charge level SLIM, and consequently, the battery management computer gives the order to the on-board charger to stop the charging sequence. The state of the charging sequence changes from ON to OFF at the instant ts.

[0063] The current charge level SOCC is capped at the SLIM value as shown by the horizontal flat line 54.

[0064] If the SLIM limit charge level is equal to 100%, the recharging sequence is not interrupted by the method promoted here, but the recharging sequence is interrupted under nominal conditions, i.e. when the total useful load is reached.

[0065] According to an optional feature, an information step is also provided for the user. The user can thus be informed that it is normal for the charge level visible on the on-board instruments to indicate a value less than 100%.

[0066] According to an optional feature, the temperature information is supplemented by auxiliary local temperature information available through an internet connection, via a connected system of the vehicle or via a multifunction mobile telephone of the user connected locally to an electronic system of the vehicle.

[0067] The internet connection also allows you to benefit from local weather forecasts, including short-term, geolocated temperature forecasts. The value of the load limitation threshold can therefore depend on forecasts of rising or falling temperatures over the following hours.

[0068] For this purpose, as illustrated in [Fig. 1], the vehicle 7 can communicate with a remote server 82. More specifically, the vehicle can comprise a telematics system connected to the internet and which can access at least one weather forecast server. According to an alternative solution, the user of the vehicle can have a multifunction smartphone 81 connected to a cellular network as known per se, and furthermore coupled by means of a Bluetooth™ type coupler to one of the on-board computers of the vehicle.

Claims

Claims

1. Method for managing a recharging sequence of a battery pack (2) of an electric vehicle (7), in a vehicle comprising said battery pack, at least one on-board computer (4) connected to an outside temperature sensor (74) and a battery management computer (1), characterized in that the method comprises: - a step of measuring an outside temperature, and making available via the on-board computer (4) the outside temperature information, - a step of determining a limit charge level threshold (SLIM) as a function at least of the outside temperature information, by the battery management computer, - a step of evaluating a current charge level (SOCC) of the battery pack by the battery management computer (1), - a step of interrupting a recharging sequence in progress if the current charge level exceeds the limit charge level threshold.

2. Method according to claim 1, characterized in that the limit charge level threshold is expressed as a percentage of a total capacity usable by the user.

3. Method according to any one of claims 1 to 2, characterized in that the limit charge level threshold is between 60% and 85% of a total useful capacity if the outside temperature information is greater than a temperature switching threshold between 35°C and 45°C.

4. Method according to any one of claims 1 to 3, characterized in that the limit load level threshold is established as a function of the outside temperature, according to a map resulting from validation tests.

5. Method according to any one of claims 1 to 4, characterized in that the temperature information is supplemented by auxiliary local temperature information available through an internet connection, via a connected telematics system of the vehicle or via a multifunction mobile telephone of the user coupled locally to an electronic system of the vehicle.

6. Method according to any one of claims 1 to 5, characterized in that the current charge level (SOCC) is evaluated during the recharge at least by integrating over time a value of electric current which enters the battery pack and in reference to voltage measurements made at rest.

7. Method according to any one of claims 1 to 6, characterized in that a step of providing information to the user is also provided.

8. Vehicle comprising a battery pack, at least one on-board computer (4) connected to an outside temperature sensor (74) and a battery management computer (1), characterized in that the on-board computer and the battery management computer are configured to implement the method according to one of claims 1 to 7.

9. System comprising a vehicle according to claim 8 implementing the method according to claim 5, and a remote server (82) configured to deliver geolocated weather information as well as short-term weather forecasts.

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