Improved cooling of battery systems

Abstract

The invention relates to a battery system (10) comprising a battery housing (12) in which a battery module (14) having a plurality of interconnected battery cells (16) is arranged, wherein the battery system (10) further comprises a cooling system (18) such that the battery cells (16) are at least partially surrounded by an electrically insulating cooling housing (20), the cooling housing being designed to conduct a cooling fluid (22) that contacts the battery cells (16), and wherein a measuring circuit (24) is also provided for measuring the electrical insulation resistance of the cooling fluid (22), wherein the measuring circuit (24) is part of a sensor circuit (26) for monitoring insulation, which is designed to measure the electrical insulation resistance between the battery housing (12) and a voltage-carrying part of the battery module (14).

Description

Technical Field

[0001] The present invention relates to a battery system with improved cooling of battery modules. In particular, the present invention relates to a battery system in which the functional state of a cooling fluid can be effectively checked. The present invention also relates to the use of an insulation monitor for checking the functional state of a cooling fluid in a battery module. Background Art

[0002] To cool batteries during operation, they may be exposed to a cooling fluid. To avoid negative effects, cooling fluids are often electrically insulating. If the electrical conductivity of the cooling fluid increases, this can negatively impact the performance and safety of the cooling fluid or the battery system.

[0003] US Pat. No. 9,880,226 B2 describes a system and method for monitoring the conductivity of a cooling fluid flowing in a fuel cell system in a vehicle having a chassis. The fuel cell system includes a fuel cell stack and a battery, the fuel cell stack being electrically coupled to a stack bus, and the battery being electrically coupled to a drive bus. The method includes: operating the fuel cell system; measuring a first insulation resistance at a first power level; measuring a first stack voltage; and measuring a first battery voltage. The method also includes: operating the fuel cell system at a second power level; measuring a second insulation resistance; measuring a second stack voltage; and measuring a second battery voltage. The method calculates an average stack cooling resistance from the first and second insulation resistances, the first and second stack voltages, and the first and second battery voltages, and then calculates the coolant conductivity from the average stack cooling resistance.

[0004] US Pat. No. 7,654,248 B2 describes a method and apparatus for monitoring coolant conductivity in a fuel cell that supplies current via positive and negative buses. The method includes: measuring a first voltage on the positive bus; measuring a second voltage on the negative bus; applying a resistor between the positive bus and a reference potential; measuring a third voltage on the positive bus after applying the resistor for a period of time; and determining insulation resistance based on the measured voltages. The insulation resistance is a function of coolant conductivity. Summary of the Invention

[0005] The present invention relates to a battery system comprising a battery housing in which a battery module comprising a plurality of interconnected battery cells is arranged, wherein the battery system further comprises a cooling system such that the battery cells are at least partially surrounded by an electrically insulating cooling housing, the cooling housing being constructed for conducting a cooling fluid that contacts the battery cells, and wherein a measuring circuit for measuring the electrical insulation resistance of the cooling fluid is further provided, wherein the measuring circuit is part of a sensor circuit for monitoring insulation, the sensor circuit being designed for measuring the electrical insulation resistance between the battery housing and a voltage-conducting part of the battery module.

[0006] Such a battery system can provide reliable and stable cooling for battery modules or battery cells and can thereby realize a peripheral device with few components. In other words, such a battery system can realize reliable operation of the battery cells in a cost-effective manner.

[0007] A battery system is thus described. This battery system includes a battery housing in which a battery module with a plurality of interconnected battery cells is arranged. The battery housing can be made of metal, for example, and serves to protect the components located in the battery housing from mechanical and other loads. The battery cells located in the battery housing can be interconnected in a known and optional manner. Within the meaning of the present invention, the battery cells can be connected in series or in parallel.

[0008] Furthermore, the battery cell can in particular be a storage battery cell. As a non-limiting example, the storage battery cell can be a lithium cell or a lithium-ion cell.

[0009] It is further provided that the battery system has a cooling system, wherein the cooling system serves to cool the battery cells.

[0010] This is advantageous in particular because cooling the batteries or battery cells during operation increases the maximum available power and also increases the service life of the installed battery cells. Significant safety gains can also be achieved in this way.

[0011] The cooling system is designed such that the battery cells are at least partially surrounded by an electrically insulating cooling housing, which is configured to conduct a cooling fluid that contacts the battery cells. In other words, the cooling fluid flows directly through or around the battery cells or their cell housings. This can be easily achieved by designing the cooling housing accordingly, such that it at least partially surrounds the battery cells and seals them from the battery cells or their cell housings. The cooling fluid can particularly preferably be a cooling liquid.

[0012] This design allows for particularly effective cooling, since the coolant or cooling fluid used is in direct contact with the battery cells. However, it should be noted that the cell housings of many cell types are under voltage. To avoid undesirable effects such as electrolysis of the cooling fluid, in particular a cooling liquid, or self-discharge between cells with different electrical potentials, it is preferred to use a non-conductive or only slightly conductive cooling fluid.

[0013] The properties of the cooling fluid can change over time due to moisture absorption, aging effects, contamination, or incorrect filling of the cooling circuit. This can lead to an insignificant increase in electrical conductivity, which can result in safety problems, such as electrolysis, or usability problems due to increased spontaneous discharge.

[0014] In order to reliably detect such changes in the cooling fluid quality and, if necessary, react accordingly, a measuring circuit for measuring the electrical insulation resistance of the cooling fluid is provided for the battery system described herein. This allows for direct and real-time detection of adverse changes in insulation resistance or electrical conductivity, potentially resulting in a reduction in safety. This allows for reliable reaction to such hazards, making it virtually possible to avoid negative effects due to a reduction in cooling fluid quality.

[0015] The measuring circuit is defined as part of an insulation monitoring sensor circuit designed to measure the electrical insulation resistance between the battery housing and the voltage-carrying part of the battery module. For this purpose, the housing and the corresponding voltage-carrying part can be contacted, for example, by a voltmeter. This sensor circuit, also known as an insulation monitor, is used to monitor the insulation resistance of the cooling fluid in the battery system described herein.

[0016] By using such a sensor circuit or insulation monitor to monitor the electrical insulation quality of the cooling fluid, safety problems such as electrolysis and increased self-discharge of directly cooled battery cells can be reliably avoided, with only limited or reduced peripheral equipment being required.

[0017] Thus, for example, there is no need to use additional conductivity sensors or ultrasonic sensors for ascertaining the insulation quality of the cooling fluid, since these sensors in part entail considerable additional costs.

[0018] In contrast, the battery system described here provides for monitoring the electrical conductivity or insulation quality of the cooling fluid using already standardized sensor circuits for monitoring insulation, particularly in high-voltage batteries, or using insulation monitors. This allows for significant reliability and safety gains without requiring any or at least minimal additional costs or without requiring significant expansion of peripheral equipment.

[0019] The insulation monitor used here is characterized, for example, by having an electrical connection to one or more battery cells and to ground. The insulation monitor is preferably designed to output a signal, such as a fault signal, to the battery management system via this connection as soon as the resistance between the high-voltage source and ground falls below a threshold value or significantly deviates from a predetermined value. The insulation monitor is thus designed to detect contact between the battery housing and the live part of the battery.

[0020] If the insulation monitor now detects an insulation fault in the battery housing, for example, it reports the fault to a higher-level system such as a vehicle system or a vehicle control system (e.g., a vehicle), and opens a switching mechanism that is closed in normal operation depending on the current operating state, thereby isolating the battery from the higher-level system.

[0021] This creates significant synergistic effects in the battery system described here, as even with reduced insulation quality of the cooling fluid, a fault in the battery management system can be detected and appropriate measures can be taken. These measures can include displaying the fault or even disconnecting the battery. The measures taken can be dependent, in particular, on the magnitude of the detected insulation resistance or on the magnitude of the electrical conductivity measured by the insulation monitor.

[0022] The battery system described can be used in PHEV or EV modules, in which the cylindrical cells are directly cooled using a non-conductive coolant. Exemplary applications can be found in automotive batteries for at least partially electrically driven vehicles, although the battery system is not limited to this application.

[0023] It may be preferred that the voltage-carrying component of the battery be at least one of the positive electrode, the negative electrode, and the cell housing of the battery module. This design allows for the use of conventional sensor assemblies or conventional insulation monitors, as this design is equivalent to arranging conventional insulation monitors, particularly in high-voltage batteries. As a result, the aforementioned advantages of synergy and reduced peripheral equipment can be particularly effectively utilized in this design.

[0024] Furthermore, it may be preferred if the voltage-carrying part is insulated from the housing by the cooling fluid. This design allows for a particularly simple and efficient implementation of the battery system. This is because the insulation monitor or sensor assembly can be designed in this way so that it can also measure the insulation resistance of the coolant or cooling fluid. This design thus allows for the aforementioned advantages, particularly regarding synergy effects and reduced peripheral equipment, in a particularly efficient manner.

[0025] Furthermore, it may be preferred that the sensor circuit for monitoring the insulation is part of a battery management system, which is designed to transfer the battery to a safe state or output a warning message if the electrical insulation resistance of the cooling fluid falls below a predeterminable value. In this embodiment, not only can the insulation quality or electrical conductivity of the cooling fluid be determined, but the battery management system, i.e., the control unit of the battery system, can also react directly if the insulation quality is not within a predeterminable range. This can, for example, prevent the occurrence of undesirable effects such as electrolysis of the cooling fluid, particularly cooling liquid, or automatic discharge between cells with different electrical potentials. This can be achieved, for example, by transferring the battery to a safe state, for example by disconnecting the battery, or by outputting a warning message, for example to the vehicle driver.

[0026] It may also be preferred that the cooling fluid be guided via an electrically conductive coolant connection connected to the cooling housing, and that the coolant connection also be electrically conductively connected to the battery housing. In this design, an electrical connection between the cooling fluid and the housing can be easily established, which effectively allows for determining the insulation quality of the cooling fluid, since the performance of the insulation monitor can be easily utilized based on its measurement assembly, as described above. The electrically conductive coolant connection can be designed, for example, as a pipe or a similar element, and / or made of metal or electrically conductive plastic. Other options for designing the coolant connection include, for example, metal-coated plastic. Furthermore, a coolant connection is particularly a component or region that is connected to the cooling housing or is part of the cooling housing, and the cooling housing is electrically conductively connected to the battery housing.

[0027] It is also preferred to provide an electrode that projects into the cooling fluid, wherein the electrode is part of a sensor circuit that monitors the insulation. This feature allows the cooling fluid to be electrically connected to the sensor circuit that monitors the insulation or to the insulation monitor without requiring significant structural measures. In other words, this feature allows the battery system to be easily integrated into existing designs. The electrode can be designed, for example, as a small plate that is connected, for example, to a cable harness of the insulation monitor and projects into the cooling fluid and, for example, is surrounded by the cooling fluid.

[0028] Furthermore, it may be preferred to provide electrically conductive tubes, such as metal tubes, between the battery cells and through which the cooling fluid passes, which serve as electrodes of the sensor circuit that monitors the insulation. This design also allows for simple implementation in existing battery systems with insulation monitors.

[0029] It may also be preferred if the cooling housing is designed to cool all battery cells located in the battery housing. In this design, the cooling fluid can flow into an inlet extending into the cooling housing and, after circulating through all battery cells, out of the cooling housing or the outlet. This feature allows for a particularly simple design of the cooling system, and thus of the battery system.

[0030] Furthermore, it may be preferred that the battery system is a high-voltage battery system. In this embodiment, it can be particularly advantageous if, in particular with high-voltage batteries, insulation monitoring is specified in accordance with standards, such as in EU Directive ECE-R 100. Within the meaning of the present invention, a high-voltage battery is a system in which the maximum system voltage is greater than 60V, typically between 200V and 800V.

[0031] According to the foregoing, the battery system allows efficient measurement of the electrical insulation resistance of the cooling fluid without the need for cumbersome peripheral equipment, since a standard-compliant insulation monitor is used.

[0032] The subject matter of the present invention is also the use of a sensor circuit for a battery system as described above, wherein the sensor circuit is designed to measure the electrical insulation resistance between the battery housing and the voltage-carrying part of the battery module for determining the electrical insulation resistance of the cooling fluid of the cooling system of the battery system.

[0033] Further advantages and advantageous embodiments of the subject matter of the invention are illustrated by the drawings and will be described in the subsequent description, wherein the features described may be the subject matter of the invention individually or in any combination, unless the text clearly indicates otherwise. It should be noted that the drawings have only the described characteristics and are not to be considered as limiting the invention in any way. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a schematic diagram of a battery system according to the present invention. DETAILED DESCRIPTION

[0035] exist Figure 1 , a battery system 10 is shown having a battery housing 12, in which a battery module 14 with a plurality of interconnected battery cells 16 is arranged. The battery system 10 also has a cooling system 18, such that the battery cells 16 are at least partially surrounded by an electrically insulating, or in other words, non-conductive, cooling housing 20, which is designed to conduct a cooling fluid 22 that contacts the battery cells 16. The cooling fluid 22 thus flows directly through or around the battery cells 16.

[0036] The cooling housing 20 is connected to coolant connections 28, 30, through which the cooling fluid 22 can flow into or out of the cooling housing 20 and which are connected to an external cooling circuit. The coolant connections 28, 30, which are designed as pipes, are electrically connected to the battery housing 12.

[0037] Furthermore, a measuring circuit 24 is provided for measuring the electrical insulation resistance of the cooling fluid 22. It is provided that the measuring circuit 24 is part of an insulation-monitoring sensor circuit 26, which is designed to measure the electrical insulation resistance between the battery housing 12 and the voltage-carrying parts of the battery module 14, in particular at least one of the positive pole 34, the negative pole 36, and the cell housing 38. The positive pole 34 and the negative pole 36 of the battery module 14, as well as all the cell housings 38 of the battery cells 16, are electrically isolated from the battery housing 12 and the coolant connections 28, 30 by the non-conductive cooling fluid 22 flowing through the insulation paths 40, 42, which can also be referred to as an IT system.

[0038] It is also provided here that the insulation monitoring sensor circuit 26, also called the insulation monitor, is part of a battery management system 32, which is designed to transfer the battery system 10 to a safe state or output a warning message when the electrical insulation resistance of the cooling fluid 22 is below a predefined value.

[0039] In other words, the insulation monitor in the battery management system 32 continuously monitors whether the insulation resistance between the battery housing 12, which serves as ground (GND), and the positive terminal (34, HV+) or the negative terminal (36, HV-) is sufficient, also known as high-voltage safety. For this purpose, the measuring circuit 24 is designed as follows.

[0040] An electrical connection 44 is provided between the coolant connection 28, which is grounded via an electrical connection to the battery housing 12, and the battery management system 32, and an electrical connection 46 is provided between the positive pole 34 and the battery management system 32, to enable voltage measurement. Furthermore, an electrical connection 48 is provided between the coolant connection 30, which is grounded via an electrical connection to the battery housing 12, and the battery management system 32, and an electrical connection 50 is provided between the negative pole 36 and the battery management system 32, to enable voltage measurement.

[0041] If the cooling fluid 22 is contaminated with conductive additives such as water, or if the cooling circuit is incorrectly filled with a conductive fluid, the resistance of the cooling fluid 22 decreases significantly. In this case, current flows between the coolant connection 28 and the cell housing 38. An insulation fault occurs between the positive terminal HV+ or the negative terminal HV- and ground GND. This fault is reliably detected by the sensor circuit 26 or the measuring circuit 24 of the battery management system 32, and the battery module and / or the vehicle equipped with this battery system 10 can be disconnected and / or a warning message can be output.

[0042] For this battery system 10, it is therefore possible to only run standard lines to the positive terminal HV+, the negative terminal HV-, and the ground GND in the circuit of the insulation monitoring system on the battery management system 32, and not to use other sensor elements. Nevertheless, the battery system 10 can still disconnect the battery module 14 or issue a fault message in the event of a filling error.

Claims

1. A battery system comprising a battery housing (12) in which a battery module (14) having a plurality of interconnected battery cells (16) is arranged, wherein: The battery system (10) further comprises a cooling system (18), such that the battery cells (16) are at least partially surrounded by an electrically insulating cooling housing (20), the cooling housing being designed to conduct a cooling fluid (22) in contact with the battery cells (16), and wherein a measuring circuit (24) is also provided for measuring the electrical insulation resistance of the cooling fluid (22), characterized in that the measuring circuit (24) is part of a sensor circuit (26) for monitoring insulation, which is designed to measure the electrical insulation resistance between the battery housing (12) and a voltage-carrying part of the battery module (14), wherein the sensor circuit is a standard circuit for insulation monitoring in a battery management system (32) of a high-voltage battery.

2. The battery system according to claim 1, characterized in that The voltage-carrying portion of the battery module (14) is at least one of the positive electrode (34), the negative electrode (36) and the cell housing (38) of the battery module (14).

3. The battery system according to claim 1 or 2, characterized in that The voltage-carrying portion is insulated from the battery housing (12) by the cooling fluid (22).

4. The battery system according to claim 1 or 2, characterized in that The sensor circuit (26) for monitoring the insulation is part of a battery management system (32) which is designed to transfer the battery system (10) to a safe state or to output a warning message if the electrical insulation resistance of the cooling fluid (22) falls below a predeterminable value.

5. The battery system according to claim 1 or 2, characterized in that The cooling fluid (22) can be guided via electrically conductive coolant connections (28, 30) connected to the cooling housing (20), and the coolant connections (28, 30) are also electrically conductively connected to the battery housing (12).

6. The battery system according to claim 1 or 2, characterized in that An electrode is provided which projects into the cooling fluid (22), wherein the electrode is a component of a sensor circuit (26) for monitoring the insulation.

7. The battery system according to claim 1 or 2, characterized in that An electrically conductive tube is provided between the battery cells (16) and through which the cooling fluid (22) passes, and which serves as an electrode of a sensor circuit (26) that monitors the insulation.

8. The battery system according to claim 1 or 2, characterized in that The cooling housing (20) is designed to cool all battery cells (16) located in the battery housing (12).

9. The battery system according to claim 1 or 2, characterized in that The battery system (10) is a high-voltage battery system.

10. Use of a sensor circuit (26) in a battery system (10) according to any one of claims 1 to 9, wherein: The sensor circuit (26) is designed to measure the electrical insulation resistance between the battery housing (12) and a voltage-carrying part of the battery module (14) for determining the electrical insulation resistance of a cooling fluid (22) of a cooling system of the battery system (10).

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