LU500544B1 - Motor vehicle battery system - Google Patents

Abstract

The present invention relates to a battery system (3) for a motor vehicle comprising: - a battery assembly (11), comprising an airtight casing (13), the casing (13) containing: a first battery (15) comprising a plurality of battery cells (17), a direct current - direct current converter (19), means for measuring the temperature of the battery cells (17), and means for thermal regulation of the converter (19) and of the cells battery (17), the battery system (3) further comprising: - a second battery (25) arranged outside the housing (13). The invention also relates to a method for operating such a battery system (3), as well as a method for pre-starting a motor vehicle comprising such a battery system (3).

Description

Description

Title of the invention: Automotive vehicle battery system

The invention relates to a battery system for a motor vehicle, a method for operating a battery system for a motor vehicle, and a method for pre-starting a motor vehicle comprising a battery system.

There is already known in the state of the art, a battery system for a motor vehicle comprising a battery assembly provided with a casing containing a first battery comprising a plurality of battery cells, and a second battery arranged outside the housing. In order to allow the transfer of electrical energy between the first battery and the second battery, the battery system comprises a direct current—direct current converter. Such a system is particularly useful in the case of light electric hybridization vehicles comprising a heat engine and an electric element such as for example an alternator-starter, also known in English as a “Mild Hybrid Electric Vehicle” or MHEV. This type of vehicle must be able to operate at temperatures between -40°C and +60°C. However, the first battery can only be charged from a minimum temperature threshold. When the temperature of the first battery is below this threshold, it must be reheated in order to allow it to be charged. For this, it is usually provided to have a heating element in the housing, for example an electrical resistor.

Nevertheless, such a heating element does not allow the first battery to be charged after a very short time interval after a cold start. Thus, the storage of regenerative electrical energy, for example following a deceleration of the motor vehicle, is not possible before a relatively long time interval after a cold start of the motor vehicle. In addition, such a heating element consumes a lot of energy, clutters the internal space of the casing and weighs down the motor vehicle for a potentially rare use, namely only when the temperature of the first battery is too low, because lower than the aforementioned minimum temperature threshold. More generally, in order to allow optimal operation, battery cells must be thermally regulated.

The object of the invention is in particular to provide a battery system and a method of operating such a battery system making it possible to make a battery comprising a plurality of battery cells available for charging quickly when the initial temperature of the battery is too low.

To this end, the subject of the invention is a battery system for a motor vehicle comprising: - a battery assembly, comprising a closed casing, the casing containing: a first battery comprising a plurality of battery cells, a direct current-direct current converter , means for measuring the temperature of the battery cells, and means for thermal regulation of the converter and of the battery cells, the battery system comprising: - a second battery disposed outside the casing, the converter being configured to operate in a first normal discharge operating mode in which the converter discharges the first battery to the second battery, a second normal charging operating mode in which the converter charges the first battery from the second battery, and a third operating mode discharge gradient in which the converter discharges the first battery ver s the second battery, and wherein the efficiency of the converter is lower than that of the first normal operating mode.

According to other optional characteristics of the battery system taken alone or in combination: - The case is sealed against humidity and dust, for example airtight. - The efficiency of the converter in the third degraded operating mode is lower by at least 10%, preferably by at least 15%, than that of the first normal operating mode. - The thermal regulation means comprise a closed circuit of thermal regulation fluid, preferably air, which comprises a ventilation unit generating a circulation of thermal regulation fluid in the housing, a heat exchanger for the thermal regulation fluid connected by thermal conduction to the converter, and thermal regulation fluid passage channels between the battery cells. Thus, it is ensured that the thermal regulation of the battery cells is carried out in a homogeneous manner. - The ventilation unit comprises at least one fan, preferably a plurality of fans, for example six fans.

- The converter comprises a heat dissipation plate, preferably metallic, more preferably aluminum, the heat exchanger comprising fins connected by thermal conduction to the heat dissipation plate. Thus, there is a simple way to transfer the heat emitted by the converter to the heat exchanger. - The heat dissipation plate is coated with a thermally conductive paste, the fins being placed in contact with the paste and/or with the heat dissipation plate. Thus, the heat conduction between the fins and the heat dissipation plate is optimally achieved. - The heat exchanger is a liquid heat exchanger - thermal control fluid, and comprises a pipe for the liquid, the pipe for the liquid forming an open loop configured to be in fluidic connection with a liquid circuit external to the housing , and the fins extending from the liquid tubing.

Thus, the temperature regulation is optimized, because the liquid can be used, depending on its temperature, to regulate the temperature not only of the battery cells but also of the converter. - The liquid is a mixture of glycol and water. Thus, it is possible to use a cooling circuit of the motor vehicle already usually used for other purposes, in order to cool the converter and the battery cells. - The thermal regulation fluid is air. Thus, because the specific heat capacity of the air is low, the latter heats up very quickly, especially in contact with the fins of the heat exchanger. Due to this, the heat emitted by the converter can be quickly transmitted to the battery cells. - The first battery is configured to deliver a first output voltage, the second battery being configured to deliver a second output voltage lower than the first output voltage. - The first battery is configured to deliver a first output voltage of 48V, and the second battery is configured to deliver a second output voltage of 12V. - The first battery has twelve battery cells.

The invention also relates to a method of operating a battery system for a motor vehicle as defined above, comprising the following steps: a) detection of the temperature of the battery cells, b) when the temperature detected at the step a) is below a predetermined temperature threshold, charging the second battery from the first battery via the converter, the converter operating in the third degraded operating mode, and heat transfer between the converter and the battery cells by means of thermal regulation.

As the energy used by the converter comes from the battery cells of the first battery, the process of charging the second battery by discharging the first battery actually increases the internal temperature of the battery cells. Thus the combination, on the one hand of the heat generated by this process of discharging the second battery, and on the other hand of the heat generated by the converter in an operating mode with degraded efficiency then transmitted to the battery cells by means of thermal regulation, makes it possible to generate a greater quantity of heat and thus to heat up the battery cells more quickly.

According to other optional characteristics of the operating method taken alone or in combination: - The predetermined temperature threshold is between 0°C and 10°C, preferably equal to 0°C. - Step b) is stopped when the second battery reaches a maximum state of charge.

This prevents damage to the second battery. - Step b) is stopped when the first battery reaches a minimum state of charge.

Thus, damage to the first battery is avoided. - The operating method comprises the following steps: c) when step b) is running, detecting the temperature of the battery cells, d) when the temperature detected in step c) is greater than or equal to at the predetermined threshold, step b) is stopped. Thus, the quantity of energy used is optimized to allow the first battery to reach the predetermined temperature threshold, allowing it for example to be charged. As a result, the storage of recuperated electrical energy, for example following a deceleration of the motor vehicle, is quickly made possible. - The method of operation comprises the following step: e) after step d), charging the first battery from the second battery via the converter, the converter operating in the second normal operating mode, and thermal regulation of the converter and of the battery cells by the thermal regulation means. Thus, it is ensured to charge the first battery optimally as soon as it is at the predetermined temperature threshold, allowing it for example to be charged.

- Step e) is stopped when the second battery reaches a minimum state of charge.

This prevents damage to the second battery. - Step e) is stopped when the first battery reaches a predetermined state of charge. Thus, it is ensured to charge the first battery only to the predetermined state of charge, which allows it, for example, to supply a highly power-consuming element, such as a catalyst. In this way, the electrical energy stored in the motor vehicle is optimized.

Another subject of the invention is a method for pre-starting a motor vehicle comprising a battery system as defined previously, which comprises the following steps: - detection of a probable start event of the motor vehicle, - when the start event probability of the motor vehicle is detected, execution of the operating method as defined above.

Thus, the operating method is executed in advance before starting the motor vehicle, which makes it possible to make the first battery available for charging all the earlier.

According to other optional characteristics of the pre-starting method taken alone or in combination: the probable start event of the motor vehicle is chosen from the group comprising an opening of a door of the motor vehicle, preferably of the driver's door, a proximity detection of a passive key of the motor vehicle, remote unlocking of the motor vehicle, preferably by a radio key forming a remote control.

Thus, an event already existing on a motor vehicle is advantageously used as a probable starting event. The driver of the motor vehicle does not have to perform a specific action, distinct from the actions that he usually performs before starting the vehicle, in order to cause the execution of the operating method.

Brief description of figures

The invention will be better understood on reading the following description, given solely by way of example and made with reference to the appended drawings in which: [Fig. 1] Figure 1 is a schematic view of a motor vehicle comprising a battery system according to one embodiment; [Fig. 2] Figure 2 is a schematic view of the battery system according to the embodiment shown in Figure 1;

[Fig. 3] Figure 3 is a schematic view of a detail of the battery system according to the embodiment shown in Figure 2; [Fig. 4] FIG. 4 is a diagram illustrating an exemplary method of pre-starting a motor vehicle comprising a battery system and an exemplary method of operating a battery system.

detailed description

In all the figures, the same references relate to the same elements.

In this detailed description, the following embodiments are examples. Although the description refers to one or more embodiments, this does not mean that the characteristics apply only to a single embodiment. Simple features of different embodiments may also be combined and/or interchanged to provide other embodiments.

FIG. 1 schematically represents a motor vehicle 1, in this example with light hybridization, comprising a battery system 3 according to one embodiment, a heat engine M comprising a catalyst C for exhaust gases and an alternator-starter A. In In this example, the motor vehicle 1 also includes an electronic control unit 5, which includes means for detecting the proximity of a passive key 7 of the motor vehicle 1. Alternatively or additionally, the electronic control unit 5 includes a radio receiver controlling the locking, respectively the unlocking, of the doors of the motor vehicle 1, on the basis of a command transmitted remotely by a radio key forming a remote control. Alternatively or additionally, the electronic control unit 5 comprises a detector of the opening of a door of the motor vehicle, preferably the driver's door. In this example, the motor vehicle 1 further comprises a cooling circuit 9 of the combustion engine M, in which a liquid circulates, for example a mixture of glycol and water.

Figure 2 schematically shows a battery system 3 according to the embodiment shown in figure 1. In this example, the battery system 3 comprises a battery assembly 11.

The battery assembly 11 comprises a closed casing 13, which in this example is impervious to humidity and dust. The housing 13 is for example made of a thermoplastic material. The casing 13 contains a first battery 15 comprising a plurality of battery cells 17. The casing 13 also contains a direct current-direct current converter 19, means 21 for measuring the temperature of the battery cells 17, and means for regulating thermal converter 19 and battery cells 17.

The battery system 3 also includes a second battery 25 arranged outside the casing. The first battery 15 is configured to deliver a first output voltage, the second battery 25 being configured to deliver a second output voltage lower than the first output voltage. The first battery 15 is configured to deliver a first output voltage of 48V, and the second battery 25 is configured to deliver a second output voltage of 12V. In this example, the first battery 15 comprises twelve battery cells 17. However, this number is variable depending on the arrangement of the battery cells and their electrical configuration in series and/or in parallel.

Converter 19 is electrically connected to first battery 15 and to second battery 25. Converter 19 is configured to operate according to a first normal discharge operating mode in which converter 19 discharges first battery 15 to second battery 25, a second normal charging operating mode in which the converter 19 charges the first battery 15 from the second battery 25, and a third degraded discharge operating mode in which the converter 19 discharges the first battery 15 to the second battery 25, and wherein the efficiency of the converter 19 is lower than that of the first normal mode of operation. In this example, the efficiency of converter 19 in the third degraded operating mode is lower by at least 10%, preferably by at least 15%, than that of the first normal operating mode. For example, the efficiency of converter 19 in the first normal operating mode is between 95% and 98%, and the efficiency of converter 19 in the third degraded operating mode is 80%.

The converter 19 includes a heat dissipation plate 27, preferably metallic, more preferably aluminum. In this example, the heat dissipation plate is coated with a thermally conductive paste 29.

The thermal regulation means comprise a closed circuit 30 of thermal regulation fluid F. In this example, the thermal regulation fluid F is air.

The closed circuit 30 of thermal regulation fluid F comprises at least one ventilation unit 31, comprising in this example six fans, i.e. half the number of battery cells 17. The closed circuit 30 of thermal regulation fluid F also comprises a heat exchanger 33 for thermal control fluid

F connected by thermal conduction to the converter 19, and passage channels 35 of thermal regulation fluid F between the battery cells 17.

The heat exchanger 33 is a liquid L-thermal control fluid F heat exchanger, and comprises a tube 37 for the liquid L and fins 39, only one of which is visible in FIG. 2. The thermal control fluid F , circulated by the ventilation unit 31, flows between the fins 39.

As shown in Figure 3, the tubing 37 for the liquid L forms an open loop configured to be in fluidic connection with a liquid circuit outside the housing 13, in this example the cooling liquid circuit 9, in which the liquid L is a mixture of glycol and water.

The fins 39 extend from the tubing 37 for the liquid L. The fins 39 are connected by thermal conduction to the heat dissipation plate 27 of the converter 19. More precisely, in this example, the fins 39 are arranged in contact with the paste 29 and/or with the heat dissipation plate 27.

Thus, the thermal regulation means make it possible to regulate the temperature, in the casing 13, of the converter 19 and of the battery cells 17, by means of the liquid L circulating in the pipe 37, which comes from the cooling liquid circuit 9.

An example of a method for pre-starting a motor vehicle 1 comprising a battery system 3 will now be described.

The pre-starting method illustrated in FIG. 3 comprises the following steps: - step 100: detection of a probable start event of the motor vehicle 1, - when the probable start event of the motor vehicle 1 is detected at step 100 , execution of an operating method as described below.

The probable start event of the motor vehicle 1 is chosen from the group comprising an opening of a door of the motor vehicle 1, preferably of the driver's door, a proximity detection of a passive key 7 of the motor vehicle 1, a remote unlocking of the motor vehicle, preferably by a radio key forming a remote control. In this example, the probable start event of the motor vehicle 1 is a proximity detection of a passive key 7 of the motor vehicle 1 or an opening of the driver's door of the motor vehicle 1. The detection is carried out by the control unit electronic 5, in particular because it comprises proximity detection means of a passive key 7 of the motor vehicle 1.

In this example of a pre-starting process, the coolant circuit 9 does not cause the liquid L to circulate in the pipe 37. Thus, the coolant circuit 9 makes it possible to regulate the temperature within the casing 13, of the cells of battery 17 and converter 19 after starting the motor vehicle

1, the liquid L circulating in the cooling circuit 9 once the thermal engine

M started.

An example of a method of operating a battery system 3 for a motor vehicle 1 will now be described.

The operating method illustrated in FIG. 4 comprises the following steps: a) detection of the temperature of the battery cells 17, b) when the temperature detected in step a) is lower than a predetermined temperature threshold, charging of the second battery 25 from the first battery 15 via the converter 19, the converter 19 operating in the third degraded operating mode, and thermal transfer between the converter 19 and the battery cells 17 by the thermal regulation means.

The predetermined temperature threshold is between 0° C. and 10° C., and is equal to 0° C. in this example. Step a) is performed by the means 21 for measuring the temperature of the battery cells 17. Step b) is for example controlled by the converter 19, which incorporates an integrated control unit. Alternatively, step b) is controlled by the electronic control unit 5.

The operating method illustrated in FIG. 4 also includes the following step 212: Step b) is stopped when the second battery 25 reaches a maximum state of charge.

The operating method illustrated in FIG. 4 also includes the following step 214: Step b) is stopped when the first battery 15 reaches a minimum state of charge.

The state of charge of the first battery 15 and the state of charge of the second battery 25 are known for example from the converter 19, which incorporates an integrated control unit. Alternatively, they are known from the electronic control unit 5.

The method of operation illustrated in FIG. 4 also comprises the following steps: c) when step b) is being executed, detection of the temperature of the battery cells 17, d) when the temperature detected in step c) is greater than or equal to the predetermined threshold, step b) is stopped. Thus, the quantity of energy used is optimized to allow the first battery to reach the predetermined temperature threshold, allowing it for example to be charged by the alternator-starter A.

The operating method illustrated in Figure 4 also includes the following step:

e) after step d), charging the first battery 15 from the second battery 25 via the converter 19, the converter 19 operating in the second normal operating mode, and thermal regulation of the converter 19 and of the cells of battery 17 by the thermal regulation means. Thus, it is ensured to charge the first battery 15 in an optimal manner as soon as the latter reaches or exceeds the predetermined temperature threshold.

The operating method illustrated in FIG. 4 also includes the following step 222: step e) is stopped when the second battery 25 reaches a minimum state of charge.

The operating method illustrated in FIG. 4 also includes the following step 224: step e) is stopped when the first battery 15 reaches a predetermined state of charge. Thus, it is ensured that the first battery 15 is charged only to the predetermined state of charge, which allows it, for example, to supply a highly power-consuming element, for example the catalyst C when starting the heat engine M of the motor vehicle 1. Thus, it is ensured that the exhaust gases from the motor vehicle 1 are treated as soon as the heat engine M is started, which reduces polluting emissions.

The operating method illustrated in FIG. 4 further comprises the following step 300: when the temperature detected in step a) is greater than or equal to a predetermined temperature threshold, charging the first battery 15 from the second battery 25 via the converter 19, the converter 19 operating in the second normal operating mode, and thermal regulation of the converter 19 and of the battery cells 17 by the thermal regulation means.

The operating method illustrated in FIG. 4 also includes the following step 322: step 300 is stopped when the second battery 25 reaches a minimum state of charge.

The operating method illustrated in FIG. 4 also includes the following step 324: step 300 is stopped when the first battery 15 reaches a predetermined state of charge. Thus, it is ensured that the first battery 15 is charged only to the predetermined state of charge, which allows it, for example, to supply a highly power-consuming element, for example the catalyst C when starting the heat engine M of the motor vehicle 1. Thus, it is ensured that the exhaust gases from the motor vehicle 1 are treated as soon as the heat engine M is started, which reduces polluting emissions.

The invention is not limited to the embodiments shown and other embodiments will be apparent to those skilled in the art. It is in particular possible to produce the liquid heat exchanger—thermal regulation fluid in a different way.

List of references 1: motor vehicle 3: battery system 5: electronic control unit 7: passive key 9: cooling circuit 11: battery assembly 13: housing: first battery 17: battery cell 19: converter 15 21: Means of temperature measurement 25: second battery 27: heat dissipation plate 29: paste 30: closed circuit 31: ventilation unit 33: heat exchanger 35: passage channel 37: tubing 39: fin

A: alternator-starter

C: catalyst

F: thermal regulation fluid

L: liquid

M: heat engine

Claims (1)

Claims [Claim 1] Battery system (3) for a motor vehicle (1) comprising: - a battery assembly (11), comprising a closed casing (13), the casing (13) containing: a first battery (15) comprising a plurality of battery cells (17), a direct current to direct current converter (19), means for measuring the temperature of the battery cells (17), and means for thermal regulation of the converter (19) and of the battery cells (17), the battery system (3) further comprising: - a second battery (25) arranged outside the housing (13), the battery system (3) being characterized in that the converter (19) is configured to operate according to a first normal mode of discharge operation in which the converter (19) discharges the first battery (15) towards the second battery (25 ), a second normal charging mode of operation in which the converter (19) charges the first battery (15) from the second battery (25), and a third degraded discharge mode of operation in which the converter (19) discharges the first battery (15) to the second battery (25), and wherein the efficiency of the converter (19) is lower than that of the first normal mode of operation. [Claim 2] Battery system (3) according to the preceding claim, in which the thermal regulation means comprise a closed circuit (30) of thermal regulation fluid F, preferably air, which comprises a ventilation unit (31 ) generating a circulation of thermal regulation fluid F in the housing (13), a heat exchanger (33) for the thermal regulation fluid F connected by thermal conduction to the converter (19), and passage channels (35) of thermal regulation fluid F between the battery cells (17). [Claim 3] Battery system (3) according to the preceding claim, in which the converter (19) comprises a heat dissipation plate (27), preferably metallic, more preferably aluminum, the heat exchanger (33) comprising fins (39) connected by thermal conduction to the heat dissipation plate (27). [Claim 4] A battery system (3) according to claim 2 or 3, wherein the heat exchanger (33) is a liquid L - thermal control fluid F heat exchanger, and comprises a pipe (37) for the L-liquid, the L-liquid tubing (37) forming an open loop configured to be in fluid connection with a liquid circuit external to the housing (13), and the fins (39) extending from the tubing (37) for liquid L. [Claim 5] A method of operating a battery system (3) for a motor vehicle (1) according to any one of the preceding claims, comprising the following steps: a) detecting the temperature of the battery cells (17), b) when the temperature detected in step a) is below a predetermined temperature threshold, charging the second battery (25) from the first battery (15) via the converter (19), the converter (19 ) operating in the third degraded operating mode, and thermal transfer between the converter (19) and the battery cells (17) by the thermal regulation means. [Claim 6] Operating method according to the preceding claim, comprising the following step: c) when step b) is in progress, detecting the temperature of the battery cells (17), d) when the temperature detected in step c) is greater than or equal to the predetermined threshold, step b) is stopped. [Claim 7] Operating method according to the preceding claim, comprising the following step: e) after step d), charging the first battery (15) from the second battery (25) via the converter (19), the converter (19) operating in the second normal operating mode, and regulating temperature of the converter (19) and of the battery cells (17) by the thermal regulation means. [Claim 8] Method of operation according to the preceding claim, in which step e) is stopped when the first battery (15) reaches a predetermined state of charge. [Claim 9] Method for pre-starting a motor vehicle (1) comprising a battery system (3) according to any one of Claims 1 to 4, which comprises the following steps: - detection of a probable start event of the motor vehicle (1), - when the probable start event of the motor vehicle (1) is detected, execution of the method of operation according to any one of claims 5 to 8. [Claim 10] Pre-starting method according to the preceding claim, in which the probable start event of the motor vehicle (1) is chosen from the group comprising an opening of a door of the motor vehicle (1), preferably of the door driver, proximity detection of a passive key (7) of the motor vehicle (1), remote unlocking of the motor vehicle (1), preferably by a radio key forming a remote control.