Device for charging a storage battery and method for regulating a charging current

Abstract

The invention relates to a charging device (10) for a storage battery (50), adapted to be connected to a current source (200). According to the invention, the charging device comprises: - a charging relay (12) adapted to be controlled to open or close the power supply to the storage battery by the current source, - an interconnection bar (14) directly connected to the charging relay and which is connected between the current source and the storage battery, - a first thermal sensor (16) adapted to measure a first temperature value at at least one point of the interconnection bar, and - a computer (18) adapted to acquire said first temperature value, to develop a charging setpoint signal as a function of said acquired first temperature value, and to send said charging setpoint signal to said current source (200).

Description

Title of the invention: Device for charging an accumulator battery and method for regulating a charging current Technical field

[0001] The present invention relates generally to accumulator batteries.

[0002] It relates more particularly to a device for charging a storage battery and a method for regulating the intensity of the charging current of this storage battery. Technological background

[0003] Electric or hybrid vehicles are generally equipped with a storage battery comprising a housing which houses several electrochemical cells connected together and providing a high voltage at the terminals of the battery, typically a voltage of several hundred volts.

[0004] It is then necessary to equip the battery with a charging device comprising electrical safety components (relay, fuse) in order to cut the current if necessary. These components are connected by means of rigid electrical conductors called interconnection bars ("busbar", according to the Anglo-Saxon term) in which the input or output current of the battery circulates.

[0005] In certain situations, the battery receives a high electrical power. This is the case, for example, during so-called rapid recharges of the vehicle battery. In these situations, the circulation of a high intensity current generates a strong increase in the temperature of the battery, in particular at the battery terminals, the charging relays and the interconnection bars.

[0006] Certain areas of the charging device are likely to experience particularly significant temperature increases; these areas are conventionally referred to as “hot spots”. The components of the charging device located at the hot spots present an increased risk of degradation.

[0007] In order to preserve these components, it is possible to modulate the intensity of the charging current. Thus, it is possible to charge the battery at a first intensity level and then, beyond a predetermined duration, to reduce this intensity in order to limit the rise in temperature within these components. This solution is however based on the determination of a thermal scenario that is as pessimistic as possible and results in an extension of the recharging time beyond what would be necessary to maintain the temperature at the hot spots below a threshold temperature allowing the integrity of the components to be preserved.

[0008] There is therefore a need for a device for charging a storage battery. making it possible to limit the temperature rise within said device while not presenting the disadvantages of existing welds. Summary of the invention

[0009] In order to overcome the aforementioned drawbacks of the prior art, the present invention proposes to limit the charging intensity of a storage battery as a function of a temperature value measured near the hot spots of the storage battery. In the charging devices of the prior art, the "hot spot" is located within the charging relay. Since measuring a temperature value within the charging relay itself is difficult, it is proposed to measure a temperature value at an accessible point as close as possible to the charging relay. Thus, according to the invention, there is proposed a device for charging an accumulator battery adapted to be connected to a current source and comprising: - a charging relay adapted to be controlled to open or close the power supply to the storage battery by the current source, - an interconnection bar directly connected to the charging relay and which is connected between the current source and the storage battery, - a first thermal sensor adapted to measure a first temperature value at at least one point on the interconnection bar, and - a computer adapted to acquire said first temperature value, to develop a charging setpoint signal as a function of said first acquired temperature value, and to send said charging setpoint signal to said current source.

[0010] The measurement of the first temperature value at at least one point of the interconnection bar makes it possible to regulate the charging intensity, via the computer, so that the temperature within the interconnection bar and the temperature within the relay is lower than a temperature threshold value making it possible to preserve the integrity of the components of the charging device, and more particularly of the interconnection bar and the charging relay. This regulation of the charging intensity as a function of the first measured temperature value advantageously makes it possible to adapt the charging intensity not as a function of the most pessimistic thermal scenario but as a function of the actual thermal charging conditions of the storage battery.The charging intensity regulation by the charging device allows the accumulator battery to be charged at an intensity higher than that determined according to the most pessimistic thermal scenario and consequently to reduce the charging time. In addition, the addition of a temperature sensor makes it possible to address the technical problem with a limited number of components.

[0011] Preferably, a second thermal sensor is provided, adapted to measure a second temperature value relative to an ambient temperature outside the charging device, and in which the computer is adapted to acquire said second temperature value and to develop the charging setpoint signal as a function of said second temperature value.

[0012] Preferably, said at least one point is located in one half of the interconnection bar which is closest to the charging relay.

[0013] Preferably, said at least one point is located less than 5 mm from an electrical contact zone between the interconnection bar and the charging relay.

[0014] The invention also relates to an electric vehicle comprising a storage battery and a charging device as mentioned above.

[0015] It also relates to a method for regulating the intensity of a charging current flowing in a charging device such as aforementioned, comprising steps of Eli) charge of the accumulator battery at a first intensity, E21) determination of a first temperature value at at least one point of the interconnection bar using a first thermal sensor, and E31) if the first temperature value determined in step E21) reaches a temperature threshold value, reduction of the intensity of the charging current of the storage battery to a second intensity.

[0016] Preferably, the method further comprises the following steps: El2) determination of a second temperature value relative to the ambient temperature, E22) determination of a maximum duration as a function of said second temperature value, E32) if a charging duration at the first intensity is greater than said maximum duration, reduction of the intensity of the charging current of the storage battery at the second intensity.

[0017] Preferably, the method further comprises the following steps: E23) determination of a charging curve representing a variation in the maximum intensity of the charging current as a function of the charging duration, E33) if, for the charging duration, the first intensity exceeds the charging curve determined in step E23), reduction of the intensity of the charging current of the storage battery, preferably to the second intensity.

[0018] Advantageously, the temperature threshold value is greater than or equal to 140°C and less than or equal to 180°C.

[0019] Advantageously also, the difference in intensity between the first intensity and the second intensity is greater than or equal to 50A and less than or equal to 150A.

[0020] Of course, the various characteristics, variants and embodiments of the invention may be combined with each other in various combinations provided that they are not incompatible or mutually exclusive. Brief description of the figures

[0021] The description which follows with reference to the appended drawings, given as non-limiting examples, will make it clear what the invention consists of and how it can be implemented.

[0022] In the attached drawings:

[0023] [Fig-1] is a schematic view of a motor vehicle according to the invention, provided of a storage battery equipped with an electric charging device;

[0024] [Fig.2] is a functional diagram of the charging device of [Fig.l];

[0025] [Fig.3] is a summary diagram of a method implemented by the device of load of [Fig.l], and on which the steps shown in dotted lines are optional;

[0026] [Fig.4] is a graph illustrating a variation of an intensity of a current of charge passing through the charging device of [Fig.l] and a measured temperature.

[0027] In [Fig.l], a motor vehicle V is shown. This could be any type of vehicle (truck, bus, car, plane, boat, etc.). This is a land vehicle, and more preferably a car.

[0028] This motor vehicle V is preferably electric or hybrid, in the sense that it comprises an electric motor 100 for its traction, supplied with electric current by a storage battery 50.

[0029] The motor vehicle V further comprises a charging device 10 used for connecting the storage battery 50 to a current source 200 external to the motor vehicle V.

[0030] This current source 200 is typically in the form of a charging terminal present on the side of a road. Such a terminal is connected to an electrical supply network and is adapted to vary the intensity of the electric current that it delivers. Here, the electric current delivered is of the direct type (as opposed to alternating).

[0031] The charging device 10 then comprises a 10A socket by which it can connect to this current source 200. This may be a physical socket or, in the case of wireless charging, an electric coil.

[0032] The motor vehicle V also includes other components which will not be detailed here, including for example a battery control system (or BMS according to the commonly used English acronym for “Battery Management System”).

[0033] The charging device 10 further comprises, to summarize: - a charging relay 12 adapted to be controlled to open or close the current supply to the storage battery 50 by the current source 200, - an interconnection bar 14 directly connected to the charging relay 12 and which is connected between the current source 200 and the accumulator battery 50, - a first thermal sensor 16 adapted to measure a first temperature value T at at least one point of the interconnection bar 14, and - a computer 18 adapted to acquire said first temperature value, to develop a charging setpoint signal as a function of said first acquired temperature value T and to send said charging setpoint signal to said current source 200.

[0034] The charging relay 12 is connected to the socket 10A. It is bistable in the sense that it is adapted to be electrically controlled between two positions, to open or close the direct current supply of the storage battery 50 by the current source 200. The charging relay 12 is, for example, configured to, before the start of charging and at the end of charging, cut the electrical connection between the storage battery 50 and the current source 200. The opening and closing of the charging relay 12 can be controlled by the computer 18 or by another computer of the vehicle (typically by the BMS). The charging relay 12 is, for example, an electromechanical relay.

[0035] The interconnection bar 14 is directly connected to the charging relay 12 in the sense that it is electrically and mechanically connected, without an intermediate element, to the charging relay 12. In the embodiment considered, the interconnection bar 14 comprises a first connection terminal connected to the charging relay 12 and a second connection terminal connected to the storage battery 50.

[0036] This interconnection bar 14 comprises, for example, a single metal bar or several bars connected in series (electrical components such as fuses being interposed between these different bars).

[0037] It has, at a first end, an opening through which it is connected to the charging relay 12. It has, at its opposite end, another opening through which it is connected to one of the terminals of the accumulator battery 50.

[0038] Alternatively, the interconnection bar could be connected, not between the charging relay 12 and the storage battery 50, but between the relay 12 and the 10A socket. In this alternative, the interconnection bar would have a first connection terminal connected to the charging relay and a second connection terminal connected to the 10A socket.

[0039] The first thermal sensor 16 is adapted to measure a first temperature value T at at least one point of the interconnection bar 14. The first thermal sensor 16 is for example a thermocouple sensor, a resistance sensor, an infrared temperature measuring device, a temperature measuring device bimetallic...

[0040] One of the hottest points of the charging device 10 is located within the charging relay 12. Since measuring a temperature value is difficult within the charging relay 12, the first thermal sensor 16 is positioned and configured so that it can measure the first temperature value on the interconnection bar 14. Here, it will be considered that the first measured temperature value is close to that of the charging relay 12, so that no difference will be made in the remainder of this description. Of course, as a variant, it would be possible to determine by calculation the temperature value within the charging relay 12 from the first temperature value T measured on the interconnection bar 14.

[0041] In the embodiment considered, and in order to be able to measure a temperature value which is as close as possible to the actual temperature within the charging relay 12, the temperature measurement point within the interconnection bar 14 is located in a half of the interconnection bar 14 which is closest to the charging relay 12. Preferably, this measurement point is located as close as possible to the contact zone between the interconnection bar 14 and the charging relay 12, for example at a distance less than or equal to 5 mm from the electrical contact zone between the interconnection bar 14 and the charging relay 12.

[0042] The computer 18 comprises a processor and a memory (or a programmable logic circuit), as well as different input and output interfaces.

[0043] Thanks to its input interfaces, the calculator is adapted to receive measured data, including the first temperature value T.

[0044] Thanks to its output interfaces, the computer is adapted to send signals to the current source 200.

[0045] Thanks to its memory, the computer stores a computer application, consisting of computer programs comprising instructions whose execution by the processor allows the computer to implement the method described below. In the variant where it includes programmable logic, its logic gates are programmed to implement this method.

[0046] This calculator 18 is thus adapted to acquire the first temperature value T and to develop a load setpoint signal as a function of this first temperature value T.

[0047] Here, it is directly this measurement on the interconnection bar 14 which will be used to develop the setpoint signal before sending it to the current source 200 so that the latter delivers a suitable intensity I. As explained above, one could alternatively start by determining by calculation the temperature value within the charging relay 12 and then develop the charging setpoint signal as a function of this temperature value within the charging relay 12.

[0048] The setpoint signal emitted by the computer 18 can be directly transmitted to the current source 200, or pass through a CAN BUS type network of the vehicle (and be stored in a memory if necessary).

[0049] The charging setpoint signal is developed so as to prevent the temperature within the charging relay 12 from exceeding a value beyond which this relay, or another component of the vehicle, would risk degradation.

[0050] This charge setpoint signal is therefore produced here as a function of the first temperature value T measured on the interconnection bar 14.

[0051] This makes it possible to recharge the storage battery 50 at a speed higher than that which would be used if, as in the prior art, only the most pessimistic thermal scenario possible were considered. Consequently, the invention makes it possible to approach the maximum charging potential permitted by the chemistry of the storage battery 50 while preserving the integrity of the charging device 10.

[0052] In the embodiment considered, the charging device 10 comprises a second thermal sensor 20 measuring a second temperature value relative to the ambient temperature outside the charging device 10. The computer 18 is then adapted to acquire this second ambient temperature value and to develop the charging setpoint signal also as a function of this second temperature value.

[0053] Thus, the regulation of the charging intensity of the accumulator battery 50 as a function of the ambient temperature can adapt to the temperature conditions in which the motor vehicle V is located.

[0054] Preferably, the computer 18 is adapted to generate the charging setpoint signal also as a function of a temperature threshold value TUm within the interconnection bar 14 that it is not desired to exceed. This threshold value is for example between 140 and 180°C. Here it is equal to 160°C.

[0055] The invention also provides a non-transitory information storage medium, in which it stores one or more sequences of instructions accessible to a processor and which, when executed by said processor, cause said processor to implement a method as described below.

[0056] The invention also relates to a method for regulating the intensity of a charging current flowing in the charging device 10, comprising at least the following three steps: Eli) charging the accumulator battery to a first intensity (I2), E21) determining the first temperature value T, and E31) if this first temperature value T reaches the threshold value Tiim, reduction of the intensity of the charging current of the storage battery to a second intensity F.

[0057] The regulation method is illustrated in detail in [Fig.3].

[0058] In practice, before starting this method, the computer 18 executes a connection protocol with the current source 200.

[0059] When this protocol results in authorization to charge the accumulator battery 50, charging begins.

[0060] As will be explained below, this charging is carried out in stages. It is therefore not intended to reduce the intensity of the charging current continuously, since this would require the use of more expensive components. On the contrary, it is intended to choose at each instant a charging current intensity from several values. Here, the choice is made from three values ​​(Ib I2 and I3). Alternatively, the choice could be made from a larger number of values.

[0061] Preliminarily, charging begins by supplying the storage battery 50 with a preliminary current I3 (see [Fig.4]).

[0062] In practice, the preliminary intensity I3 is predetermined, and the duration ti of this preliminary step is also predetermined.

[0063] The preliminary intensity I3 is equal to the maximum intensity that the storage battery 50 can receive without significantly degrading. Here it is equal to 400 A.

[0064] The duration ti is equal to the maximum duration during which the accumulator battery 50 can receive this preliminary intensity I3 without heating up too much. Here it is equal to 120 seconds.

[0065] After this time (at time ti), the intensity decreases to a first intensity I2.

[0066] The value of this first intensity is predetermined. It is for example 30 to 100 A lower than the preliminary intensity. Here it is equal to 350 A.

[0067] Step El 1 of charging the battery 50 to the first intensity I2 can then begin.

[0068] Step E21 is implemented simultaneously, so as to record the change in the first temperature value T (on the interconnection bar 14).

[0069] This first value forms a first parameter to be monitored in order to reduce the intensity of the charging current if necessary, if this value increases too much.

[0070] The objective is then to determine additional parameters to monitor, beyond which the risk of overheating would be too great, so as to determine when to reduce the intensity of the charging current to guarantee the reliability of the critical component.

[0071] Thus, still simultaneously, the computer 18 records the second ambient temperature value Tamb (step E12), via the second thermal sensor 20.

[0072] Then, during a step E22, the calculator determines a maximum duration tmax not to be exceeded, beyond which the intensity must be reduced. This maximum duration tmax is here determined as a function of the second ambient temperature value Tamb. The higher this second value, the lower the duration will be. The mapping linking these two parameters can be obtained using tests. This second parameter to be monitored thus makes it possible to predict the moment at which it will be appropriate in any case to reduce the intensity of the charging current.

[0073] Furthermore, during a step E23, the computer 18 determines a charging curve Cmax representing the maximum value of the charging current as a function of the state of the battery (temperature and charge level). In other words, this curve illustrates the maximum potential of the battery chemistry, independently of the strategies necessary for the protection of the associated electrical components. The charging current can therefore never exceed this curve. This charging curve Cmax is obtained using tests. This curve therefore forms the third parameter to be monitored.

[0074] All of these steps E1 1 to E23 are implemented in a loop, at regular time steps.

[0075] At this stage, taking into account the first temperature value T, the maximum duration tmax, and the charging curve Cmax, the computer 18 develops the charging setpoint signal corresponding to the best charging strategy for the storage battery 50. Here, this charging setpoint signal is determined at each loop, using three tests (steps E31, E32, E33) carried out on the three parameters to be monitored. Alternatively, only the first of these tests could be executed. However, the use of more tests will make it possible to regulate the intensity in a more reliable and secure manner.

[0076] Thus, during step E31, the first measured temperature value T is compared to the temperature threshold value TUm. If this first temperature value T is greater than or equal to the threshold value TUm, the intensity of the charging current of the storage battery 50 is reduced to a second intensity Ib. Otherwise, it is kept constant.

[0077] The second intensity is less than the first intensity by at least 50 A. Here it is equal to 250 A.

[0078] In [Fig.4], an example of variation of the intensity (noted Ir) of the charging current and of the first temperature value T is shown. It can be seen that in this example, the first temperature value T always remains lower than the threshold value Tiim. In this configuration, this first test does not result in a reduction in the intensity of the charging current.

[0079] During step E32, the computer 18 compares the charging duration t (at the intensity I2) with the maximum duration tmax. As soon as this maximum duration is exceeded, the intensity of the charging current of the storage battery 50 is reduced to the second intensity L. This is what is shown in [Fig.4], at the instant ti+tmax.

[0080] During step E33, if, during time t, the first intensity I2 reaches the load curve Cmax, the intensity is reduced so as to never exceed the load curve Cmax

[0081] In any case, once the intensity of the charging current has decreased to the second intensity Ib it is maintained at this value. It will decrease in accordance with the Cmax curve and when the battery is charged or when the user wishes to stop charging.

[0082] Of course, the various features, variants and embodiments of the invention may be combined with each other in various combinations to the extent that they are not incompatible or mutually exclusive.

[0083] The present invention is in no way limited to the embodiment described and shown, but those skilled in the art will be able to provide any variant in accordance with the invention.

[0084] In a variant of the invention, the charging device comprises a third thermal sensor adapted to measure a third temperature value at a point on the interconnection bar different from the point on the interconnection bar within which the first temperature value is measured, and the computer is adapted to acquire said third temperature value and to emit a charging setpoint signal as a function of said first and third acquired temperature values. This would allow a better estimation of the temperature at the charging relay.

[0085] In another variant of the invention, the charging device also comprises a humidity sensor adapted to measure a humidity level in the environment of the charging device and the computer is adapted to acquire said humidity level and to emit a charging setpoint signal as a function of said acquired humidity level. This would make it possible to reduce the charging current when the humidity is high, for safety reasons.

Claims

Claims

1. Charging device (10) for a storage battery (50), adapted to be connected to a current source (200) and comprising: - a charging relay (12) adapted to be controlled to open or close the power supply of the storage battery (50) by the current source (200), - an interconnection bar (14) directly connected to the charging relay (12) and which is connected between the current source (200) and the storage battery (50), - a first thermal sensor (16) adapted to measure a first temperature value (T) at at least one point of the interconnection bar (14), and - a computer (18) adapted to acquire said first temperature value (T), to develop a charging setpoint signal as a function of said acquired first temperature value (T), and to send said charging setpoint signal to said current source (200).

2. Charging device (10) according to claim 1, in which a second thermal sensor (20) is provided, adapted to measure a second temperature value relative to an ambient temperature outside the charging device (10), and in which the computer (18) is adapted to generate the charging setpoint signal as a function of said second temperature value.

3. A charging device (10) according to claim 1 or 2, wherein said at least one point is located in a half of the interconnection bar (14) which is closest to the charging relay (12).

4. Charging device (10) according to claim 3, wherein said at least one point is located less than 5mm from an electrical contact area between the interconnection bar (14) and the charging relay (12).

5. Electric vehicle (V) comprising an accumulator battery (50) and a charging device (10) according to one of claims 1 to 4.

6. Method for regulating the intensity (I) of a charging current flowing in a charging device (10) according to one of claims 1 to 4, comprising steps of: E11) charging the accumulator battery (50) to a first intensity (I2), E12) determining a first temperature value (T) at at least one point of the interconnection bar (14) using a first thermal sensor (16), and E31) if the first temperature value (T) determined in step E21) reaches a temperature threshold value (TUm), reduction of the intensity (I) of the charging current of the storage battery to a second intensity (Ii).

7. A regulation method according to claim 6, further comprising the following steps: E12) determining a second temperature value relative to the ambient temperature, E22) determining a maximum duration (tmax) as a function of said second temperature value (Tamb), E32) if a charging duration (t) at the first intensity (I2) is greater than said maximum duration (tmax), reducing the intensity (I) of the charging current of the storage battery (50) to the second intensity (IJ.

8. Regulation method according to claim 6 or 7, further comprising the following steps: E23) determining a charging curve (Cmax) representing the maximum value of the charging current as a function of the state of the battery (temperature and charge level), E33) if, for the charging duration (t), the first intensity (I2) exceeds the charging curve (Cmax) determined in step E23), reducing the intensity of the charging current of the storage battery (50), in accordance with the charging curve Cmax.

9. Control method according to one of claims 6 to 8, in which the temperature threshold value (TUm) is greater than or equal to 140°C and less than or equal to 180°C.

10. Regulation method according to one of claims 6 to 9, in which the difference in intensity between the first intensity (I2) and the second intensity (IJ is greater than or equal to 50A and less than or equal to 150A.

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