Cooling device for a high-voltage battery and method for detecting the ingress of water

Abstract

The invention relates to a cooling device for a high-voltage battery comprising an external cooling circuit (7) operated with cooling water. The cooling device according to the invention is characterized in that the cooling circuit (7) is coupled via a heat exchanger (6) to a battery-internal cooling circuit (1) operated with a dielectric, wherein a hydrogen sensor (8) is provided in the high-voltage battery. The ingress of water is inferred starting from a critical hydrogen concentration at the hydrogen sensor (8).

Description

[0001] Mercedes-Benz Group AG

[0002] Cooling device for a high-voltage battery and

[0003] Method for detecting water ingress

[0004] The invention relates to a cooling device for a high-voltage battery with a cooling circuit operated with cooling water. The invention also relates to a method for detecting water ingress into a high-voltage battery with such a cooling device.

[0005] High-voltage (HV) batteries are a well-established technology. They are commonly manufactured using lithium-ion technology, for example, with a liquid or solid electrolyte. The term "high voltage" refers to a direct current (DC) voltage exceeding 60V, as defined in ECE 100R. These batteries are typically designed to operate optimally within a temperature range of +10°C to approximately 40°C. Operating within this temperature range ensures high performance and a long service life. This requires, on the one hand, increasing the operating temperature at very low ambient temperatures and, on the other hand, dissipating heat generated during battery operation.

[0006] Cooling circuits are therefore used to regulate the temperature of the batteries. In a vehicle application, for example, a water-based liquid coolant is circulated within these circuits. This is typically a mixture of water and antifreeze, as is common practice for cooling vehicle components in vehicles that are not, or not fully, electrically powered. DE 102022000887 A1, for example, describes a high-voltage battery with at least one battery module and internal lines for such a liquid coolant supplied by an external cooling circuit. A valve device is provided in the area of ​​at least one of the interfaces with the external cooling circuit. This allows the cooling circuits to be separated. Furthermore, DE 102018007665 A1 describes a monitoring device for a battery cooling circuit with a sensor for detecting an insulation fault in the battery.The battery cooling circuit is fluidically coupled to the vehicle's drive cooling circuit. A level sensor is provided to determine the level of a coolant within an expansion tank of the drive cooling circuit. An evaluation unit detects a leak in the battery cooling circuit when a predefined level is undershot, and the detection of the leak is validated by signals from the sensor that detect insulation faults.

[0007] The object of the present invention is to provide an improved cooling device and a method for detecting any possible water ingress.

[0008] According to the invention, this problem is solved by a cooling device having the features of claim 1, and in particular the features of the characterizing part of claim 1. Advantageous embodiments and further developments are described in the dependent claims. Furthermore, a method according to claim 7 solves the problem. An advantageous embodiment of the method is described in the dependent claims.

[0009] The cooling system comprises, on the one hand, a cooling circuit operated with cooling water, which is hereinafter also referred to as the external cooling circuit. On the other hand, the cooling system includes an internal battery cooling circuit coupled to this external cooling circuit via a heat exchanger. This internal cooling circuit directly cools the battery and uses a dielectric fluid as the cooling medium. This allows the heat from the individual battery cells to be collected very efficiently and transferred to the external cooling circuit via the heat exchanger. In the occasional case where the battery needs to be heated, this can also be achieved in reverse by heating the cooling water, for example, via a heating element or other components requiring cooling, and then transferring the heat via the heat exchanger to the dielectric fluid of the internal battery cooling circuit.

[0010] The battery's internal cooling circuit is designed, in principle, to be robust against water ingress into the battery housing and to prevent high-voltage flashovers caused by such water ingress. In practice, however, there is always a risk that water from the external cooling circuit could enter the battery's internal cooling circuit through a leak in the heat exchanger. In this case, it is impossible to prevent electrolysis of this water within the battery, producing hydrogen and oxygen. Therefore, the cooling device according to the invention incorporates a hydrogen sensor in the high-voltage battery. Such a hydrogen sensor, as an addition to the described setup with the internal and external cooling circuits coupled via a heat exchanger, makes it extremely easy to detect any water ingress.While liquid sensors that respond to water are theoretically possible, they are complex, expensive, and must be distributed across various parts of the assembly. Since electrolysis always occurs when water enters the system, hydrogen is also produced. This hydrogen is highly volatile and, as a very light gas, typically rises towards the top of the battery casing due to gravity. A hydrogen sensor can then be used to indirectly detect water ingress.

[0011] The inventive method described in claim 7 accordingly provides that the hydrogen concentration in the high-voltage battery is monitored via the hydrogen sensor, whereby a critical hydrogen concentration is detected at the hydrogen sensor, indicating water ingress and the associated electrolysis. At this point, a corresponding alarm can be triggered and countermeasures can be initiated, such as an emergency shutdown of the battery or the affected part of the battery, or the like.

[0012] According to a highly advantageous embodiment of the cooling device according to the invention, the hydrogen sensor can be arranged in a battery housing of the high-voltage battery. A particularly advantageous embodiment provides that, in its intended use, it is arranged at the top of the battery housing, so that the hydrogen sensor is potentially positioned in the area where hydrogen is highly likely to accumulate when produced by electrolysis.

[0013] According to a further highly advantageous embodiment, the hydrogen sensor can alternatively or additionally be positioned in the vicinity of potential ignition sources to further increase safety. In particular, it can also be positioned at a potential weak point in the battery's internal cooling circuit for degassing. For example, according to a highly advantageous further development, it can be installed in an expansion tank and / or a degassing device for the dielectric cooling medium of the battery's internal cooling circuit in order to monitor the hydrogen concentration in the area where substances are outgassing from the dielectric cooling medium.

[0014] Further advantageous embodiments of the cooling device according to the invention also result from the two exemplary embodiments, which are described in more detail below with reference to the figures.

[0015] This shows:

[0016] Fig. 1 shows a schematically indicated cooling device according to the invention in a battery of a vehicle that is at least partially electrically powered, according to a first embodiment of the invention; and

[0017] Fig. 2 shows a schematically indicated cooling device according to the invention in a battery of a vehicle that is at least partially electrically powered, according to a second embodiment according to the invention.

[0018] Figure 1 schematically depicts an internal cooling circuit 1 of a cooling device. It comprises a coolant delivery system 2 and an expansion tank labeled 3. A plurality of parallel cooling lines 4 are shown between them, only some of which are marked with a reference numeral. These cooling lines 4 are part of individual battery cells within a battery (not shown here), the battery housing 5 of which is schematically indicated by the dashed line. This internal cooling circuit 1 serves for direct cooling of the battery, for which a dielectric cooling medium is used, which is therefore not electrically conductive and does not conduct electrical charge.This allows the battery to be cooled directly within its internal structure, which would not be possible with a conventional water-based cooling medium, which is always ionically conductive to a certain degree.

[0019] To dissipate heat under normal circumstances, or to absorb heat when necessary to regulate the temperature of the individual battery cells, a heat exchanger 6 is provided, which is located in a vehicle cooling circuit 7 (only partially indicated here). This vehicle cooling circuit, which is known per se, is operated in a known manner using a water-based cooling medium, for example, a mixture of water and glycol. The two cooling circuits are thermally, but not fluidically, coupled via the heat exchanger 6.

[0020] If water leaks out, for example due to an unavoidable leak in the area of ​​this heat exchanger 6, or if water otherwise enters the battery's internal cooling circuit 1, then electrolysis of this water in the individual battery cells cannot be prevented by design. This electrolysis produces hydrogen and oxygen. To detect such electrolysis and thus indirectly infer the associated ingress of water into the battery's internal cooling circuit 1, a hydrogen sensor, designated 8, is provided inside the battery housing 5. This hydrogen sensor 8 can, for example, be positioned at the top of the battery housing 5 during normal use to reliably detect the very volatile hydrogen that rises upwards.Once a certain predetermined critical hydrogen concentration is reached, water ingress into the internal cooling circuit 1 is assumed, and appropriate countermeasures can be taken.

[0021] Figure 2 shows an alternative embodiment of the cooling device. The only difference is that, in the embodiment shown in Figure 2, the hydrogen sensor 8 is located in an area that is a weak point with regard to degassing. In this case, this is the schematically indicated expansion tank 3. However, it could also be a venting device or an expansion tank with a venting device.

Claims

Mercedes-Benz Group AG Patent claims 1. Cooling device for an HV battery with an external cooling circuit (7) operated with cooling water, characterized in that the cooling circuit (7) is coupled via a heat exchanger (6) to a battery-internal cooling circuit (1) operated with a dielectric, wherein a hydrogen sensor (8) is provided in the HV battery.

2. Cooling device according to claim 1, characterized in that the hydrogen sensor (8) is arranged in a battery housing (5) of the HV battery.

3. Cooling device according to claim 2, characterized in that the hydrogen sensor (8) is arranged in a region of the battery housing (5) that is located at the top during intended use.

4. Cooling device according to claim 1, 2 or 3, characterized in that the hydrogen sensor (8) is arranged in the vicinity of a potential ignition source.

5. Cooling device according to one of claims 1 to 4, characterized in that the hydrogen sensor (8) is arranged at a potential weak point of the battery internal cooling circuit (1) for degassing.

6. Cooling device according to claim 5, characterized in that the potential weak point is an expansion tank (3) and / or a venting device.

7. Method for detecting water ingress into the internal cooling circuit (1) of an HV battery with a cooling device according to one of claims 1 to 6, characterized in that, from a critical hydrogen concentration at the hydrogen sensor (8), a conclusion is drawn about water ingress into the internal cooling circuit (1) by the electrolysis of the water that inevitably accompanies it.

8. Method according to claim 7, characterized in that an alarm is triggered and / or safety measures are initiated after reaching the critical hydrogen concentration.

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