Dielectric detection for immersion cooled automotive battery systems

Abstract

The present disclosure provides a dielectric detection for an immersion cooled automotive battery system. An automotive battery system for an electrically powered vehicle is presented. The system includes: a traction battery having an array submerged in a cooling fluid; and a pump that circulates the fluid. The pump includes circuitry configured to detect a flow of current from the traction battery through the cooling fluid to the circuitry, indicating fluid contamination or an isolation fault. The circuitry may be coupled with a high pressure pump or a low pressure pump. The battery management system receives data from the circuitry, reports a level of contamination, and may trigger a response, including disabling the array or adjusting a charge rate.

Description

Technical Field

[0001] This disclosure relates to a battery cooling system for electric vehicles. Background Technology

[0002] Immersion cooling systems can control the temperature in high-voltage battery systems, including battery cells and exposed high-voltage components. Summary of the Invention

[0003] An automotive battery system includes a traction battery and a pump. The pump includes a circuit system that detects current flow from the traction battery through a cooling fluid to the circuit system. The pump can be a high-voltage pump powered by the traction battery or a low-voltage pump powered by an auxiliary battery. The circuit system can include a resistive shunt for measuring the current flow. The circuit system can include a current sensor with both low-accuracy and high-accuracy range capabilities. The circuit system can be coupled to a battery management system that receives data from the circuit system and reports fluid contamination based on the detected current flow. The battery management system can also classify the detected current flow into associated contamination levels of the cooling fluid.

[0004] A vehicle electrical system includes a traction battery having one or more arrays immersed in a cooling fluid. A pump uses power from the traction battery to circulate the cooling fluid through the one or more arrays and includes a circuit system that can be physically electrically connected to the one or more arrays via a switch and can detect the current flow through the cooling fluid. The pump can be a high-voltage pump powered by the traction battery. Each array of the traction battery may include a battery pack monitor module that measures the current flow through the cooling fluid locally within the array. The battery pack monitor module may include a resistor or shunt attached to a high-voltage positive terminal or a high-voltage negative terminal of the array to detect voltage changes associated with the current flow through the cooling fluid. The circuit system can measure the voltage from the high-voltage positive and negative terminals to chassis ground. In some configurations, the battery pack monitor module may be coupled to a battery management system that correlates the detected current flow with vehicle diagnostic data to determine the level of contamination in the cooling fluid. The battery management system may also determine, based on the correlation, whether an isolation fault is located within the traction battery or externally. The circuit system may include multiple electrodes positioned at different locations within the cooling fluid.

[0005] An automotive system includes a housing, a traction battery, a cooling fluid contained within the housing, and a pump. The pump is powered by the auxiliary battery to move the cooling fluid through the housing and includes a resistor having terminals electrically connected to the auxiliary battery and terminals in contact with the cooling fluid. The pump may be a low-pressure pump powered by the auxiliary battery. The pump may be coupled to a battery management system that receives data indicating current flow through the cooling fluid and disables the traction battery based on the current flow. In some configurations, the battery management system may be coupled to the auxiliary battery and adjust the charging rate of the traction battery based on detected contamination levels. The resistor may be part of circuitry that detects changes in the dielectric properties of the cooling fluid, including at least one of conductivity, dielectric constant, or impedance. Attached Figure Description

[0006] Figure 1 and Figure 2 This is a schematic diagram of an electric vehicle system;

[0007] Figure 3 It is a block diagram of an electrified vehicle system; and

[0008] Figure 4 and Figure 5 This is a schematic diagram of an immersion-cooled battery system. Detailed Implementation

[0009] Detailed embodiments are disclosed herein as needed; however, it should be understood that the disclosed embodiments are merely representative and may be embodied in various and alternative forms. The drawings are not necessarily drawn to scale; some features may be enlarged or minimized to show details of specific components. Therefore, the specific structural and functional details disclosed herein should not be construed as limiting, but merely as a representative basis for teaching those skilled in the art to employ embodiments of the claimed subject matter in different ways.

[0010] The introduction of immersion cooling technology in high-voltage (HV) battery systems for electric vehicles has enabled new forms of thermal management and performance optimization. This approach, involving immersing the battery cells and associated HV components in a specially formulated dielectric fluid, offers advantages over traditional air or liquid cooling methods. Benefits include increased heat transfer capacity, a more uniform temperature distribution across the battery pack, and the potential for increased energy density. However, maintaining the integrity of electrical isolation within the system can be challenging when using immersion cooling technology.

[0011] Dielectric fluids are an integral part of immersion cooling systems. Dielectric fluids are specially designed materials that balance a variety of properties. Example immersion coolants possess high dielectric strength for maintaining electrical isolation, low viscosity for efficient cycling, high thermal conductivity for efficient heat dissipation, and chemical stability to prevent degradation under varying conditions. Selection of immersion coolant fluids includes silicone oils, synthetic hydrocarbons, and specialized fluorinated liquids. Each type of fluid is provided with a property profile, and the selection process involves considering the specific requirements of the battery system, including operating temperature range, expected lifespan, and stability considerations.

[0012] The dielectric strength of the immersion coolant plays a role in the stability and functionality of HV battery systems. The dielectric strength of the immersion coolant allows the fluid to act as an effective insulator, preventing accidental electrical connections between HV components or between HV components and the vehicle chassis. However, the dielectric strength of the fluid can be compromised by various forms of contamination. Moisture ingress, even in trace amounts, can reduce the fluid's dielectric strength. Particulate matter that may enter the system from external sources or be generated internally through component wear can create conductive pathways within the fluid. Over time, the fluid itself may undergo chemical degradation due to thermal stress or reactions with battery materials. In the event of cell damage, leakage of battery electrolyte into the coolant tank can also affect its insulating properties.

[0013] Methods for detecting isolation faults in HV battery systems focus on monitoring the electrical isolation between the HV positive (HV+) or HV negative (HV-) terminal and chassis ground. These methods may not be sufficient to fully address the specific challenges posed by immersion cooling systems. A consideration in immersion cooling systems is the possibility of a dual-fault scenario, where contamination of the coolant can lead to connections between both HV+ and HV- terminals and chassis ground. This scenario needs to be considered due to its impact on the battery, necessitating the development of improved detection and monitoring systems.

[0014] This disclosure presents a method for detecting and monitoring dielectric breakdown in an immersion-cooled HV battery system. It utilizes a pump-based sensing system to detect the voltage drop or current flow between the chassis ground and the battery terminals, which can indicate the onset of fluid contamination or dielectric breakdown. This is achieved by integrating high-precision measurement capabilities within the cooling system pump, which is capable of detecting minute voltage or current changes. The pump-based sensor is configured to measure the electrical properties between the chassis ground and both the HV+ and HV- terminals, thereby providing an early indication of potential isolation problems or cooling fluid contamination.

[0015] Pump-based measurement systems can be integrated into battery management systems (BMS), allowing for increased diagnostic capabilities. The analysis correlates current measurements with a broad range of existing diagnostic data, including cell voltage variations, battery pack self-discharge rates, and abnormal temperature distributions. The algorithm processes this data to distinguish between normal operating currents and those indicating dielectric breakdown, enabling the system to identify potential problems with high accuracy and minimal false alarms.

[0016] In the proposed method, isolation monitoring is implemented at the pump level, thus providing comprehensive battery pack-level inspection. The pump-based sensing system is capable of performing isolation checks across the entire battery pack. This approach allows for effective fault detection, enabling the system to distinguish between internal battery pack issues and externally isolated faults. The centralized nature of this monitoring system enhances overall reliability and provides data for predictive maintenance and fault diagnosis.

[0017] Passive measurement technologies configured to operate with minimal power consumption can also be incorporated. This allows for continuous fault monitoring even when the vehicle is in sleep mode. The system can also perform rapid checks when the BMS or Battery Pack Sensing Module (BPSM) is awakened, allowing for the rapid detection of potential problems without significantly impacting the vehicle's energy efficiency.

[0018] A hierarchical response system can be used to manage responses to detected faults. The severity of the detected problem determines the appropriate action, ranging from initiating diagnostic fault codes or indicators for minor cases, to limiting charge / discharge rates or power output for more serious scenarios, and even to complete vehicle start suppression and immediate protocol activation for other events. This approach balances user convenience with operational reliability to maintain vehicle functionality where possible.

[0019] The pump itself serves as a primary monitoring point within the fluid circulation system, thereby enhancing the system's monitoring capabilities. By utilizing both the high-pressure and low-pressure sides of the pump / cooler system for redundant checks, the proposed method can provide a comprehensive view of the fluid health throughout the entire circulation path.

[0020] The implementation of this detection system can involve specially configured hardware and software components. The pump is equipped with high-precision voltage and / or current measurement capabilities, enabling it to detect even the slightest electrical anomalies between the chassis ground and the battery terminals. The BMS and BPSM software can also incorporate machine learning algorithms that analyze current data in real time, taking into account factors such as normal leakage current, temperature-dependent changes in fluid conductivity, and transient currents during vehicle operation or charging.

[0021] The pump-based sensing system is equipped with dedicated processing capabilities for performing isolation checks, contributing to a robust and fault-tolerant system architecture. Data from the pumps can be aggregated and analyzed by a central BMS, which can employ pattern recognition techniques to identify and differentiate between systemic problems and localized faults. This distributed yet integrated approach allows for comprehensive monitoring while enabling rapid and accurate fault diagnosis.

[0022] Passive measurement systems can also be combined with ultra-low-power components, allowing for periodic checks even during extended periods of vehicle inactivity. This enables the detection of slowly developing faults that might otherwise be overlooked between driving cycles, improving reliability and performance.

[0023] Figure 1 and Figure 2 This is a schematic diagram of the battery monitoring system 10 within an electrified vehicle system. The traction battery 12 has an HV positive terminal 14 and an HV negative terminal 16. The HV positive terminal 14 and HV negative terminal 16 serve as the main power conduits for the electric vehicle's powertrain. The battery 12 includes multiple array modules (not depicted separately in these figures) that are electrically interconnected to form a high-capacity energy storage system capable of powering the vehicle's electric motor and auxiliary systems.

[0024] The cooling fluid 18, which completely surrounds the battery components, has multiple functions. The cooling fluid 18 provides heat dissipation from individual battery cells, ensuring a uniform temperature distribution across the entire battery 12, and acts as a dielectric to maintain electrical isolation between high-voltage components. Under normal operating conditions, the cooling fluid 18 is configured to be non-conductive, thereby maintaining the electrical integrity of the battery system.

[0025] The battery monitoring system 10 includes a pump-based sensing system 20. The pump-based sensing system 20 includes integrated measurement capabilities. The pump-based sensing system 20 is positioned in direct contact with the cooling fluid 18. The function of the pump-based sensing system 20 is to measure minute current flows that may arise due to changes in the electrical properties of the cooling fluid 18. The pump-based sensing system 20 may be able to detect extremely small voltage drops on itself, which serve as a sensitive indicator of changes in the fluid's conductivity.

[0026] The battery monitoring system 10 incorporates positive contactor 22 and negative contactor 24. These are high-voltage switching devices that control the electrical connection between battery 12 and HV load 26. Contactors 22 and 24 serve as disconnectors, allowing for rapid electrical isolation of battery 12 from the rest of the vehicle's HV system in the event of a detected fault or during maintenance procedures.

[0027] The high-resistance component 28 represents the substantially electrical isolation maintained between the battery 12 and the chassis ground 30. The high-resistance component 28 maintains the electrical integrity of the vehicle, thereby effectively preventing unintended current paths between the battery 12 and the vehicle's conductive body structure.

[0028] HV load 26 represents various HV vehicle components that draw power from traction battery 12. This may include, but is not limited to, electric drive motors, power electronics for motor control, and HV heaters or air conditioning compressors. Chassis ground 30 provides a common reference point for all vehicle electrical systems and ensures that any stray currents have a predetermined path to ground.

[0029] The physical contact between the cooling fluid 18 and the HV positive terminal 14, HV negative terminal 16, and chassis ground 30 allows the cooling fluid 18 to normalize the temperature of these components. Under normal conditions, the dielectric properties of the cooling fluid 18 prevent any current flow between these points. However, if contaminants seep into the fluid and alter its electrical properties, potential current paths may form. A pump-based sensing system 20 is configured and positioned to detect these currents, which manifest as small but measurable voltage drops across the components.

[0030] Figure 1 and Figure 2 The arrangement of the battery monitoring system 10 shown allows for continuous, real-time monitoring of the condition of the cooling fluid 18. Any increase in the conductivity of the cooling fluid 18 (which may be due to the presence of conductive contaminants 32 or disruption of the molecular structure of the cooling fluid 18) may result in a detectable current flow through the pump-based sensing system 20. This current flow generates a voltage drop across the pump-based sensing system 20, which can be accurately measured and analyzed by the battery monitoring system 10. Figure 2 As shown, when the conductive contaminant 32 has reached the threshold level, the circuit 34 between the HV positive terminal 14 and the HV negative terminal 16 is effectively formed.

[0031] Figure 3 This is a block diagram of the entire electrified vehicle system 36, illustrating the relationship between major components and subsystems. The traction battery 12 serves as the primary energy storage unit for the electrified vehicle, providing the necessary power to drive the vehicle and operate its numerous electrical systems. The traction battery 12 includes... Figure 1 and Figure 2The array module and battery monitoring system 10 are described in the diagram. An on-board charger 40 is connected to the traction battery 12. The on-board charger 40 converts AC power from an external charging station into DC power required to charge the traction battery 12. The on-board charger 40 connected to the traction battery 12 represents a high-voltage DC charging circuit. This circuit can be designed to handle high power levels, typically in the range of 50kW to 350kW, depending on the vehicle's fast-charging capabilities.

[0032] Power electronic device 42 is also connected to traction battery 12. Power electronic device 42 serves as an interface between traction battery 12 and traction motor 44. Power electronic device 42 may include an inverter system that converts DC power from traction battery 12 into AC power required by traction motor 44. Additionally, power electronic device 42 can manage bidirectional power flow, thereby enabling regenerative braking by converting kinetic energy back into electrical energy to recharge traction battery 12. Power electronic device 42 may be connected to traction motor 44, which may include HV power circuitry. HV circuitry can be configured to handle high currents, typically exceeding 1000 amperes during peak loads or regenerative braking events.

[0033] The traction motor 44 is the vehicle's main propulsion unit, responsible for converting electrical energy from the traction battery 12 into mechanical energy. The traction motor 44 can be of various types, such as a permanent magnet synchronous motor or an induction motor. The power electronics 42 connected to the traction motor 44 represent a high-voltage AC power circuit that supplies controlled, variable-frequency, and variable-amplitude power required to effectively operate the traction motor 44 over a wide range of speeds and torques.

[0034] BMS 46 is the control unit of the electric powertrain system, which monitors and manages various aspects of the operation of the traction motor 44 and the traction battery 12. BMS 46 is connected to the traction battery 12, power electronics 42, and traction motor 44. These connections represent control and communication circuitry that allows the battery management system to monitor and control these components. This circuitry carries various signals, including battery cell voltage and temperature data, state of charge and state of health estimates, coolant contamination sensor data, power demand signals to the motor controller, charging current and voltage control signals, and fault detection and mitigation commands.

[0035] The thermal management system 48 includes the traction battery 12, power electronics 42, and traction motor 44. This system is responsible for maintaining the optimal operating temperature of these components. It includes a battery monitoring system 10 for the traction battery 12 and may also include liquid or air cooling systems for the power electronics 42 and traction motor 44. The thermal management system 48 may incorporate advanced features such as heat pumps for cabin climate control and battery pre-conditioning.

[0036] The electrical connections 50 between HV components carry the main power flow within the system, such as from the traction battery 12 to the traction motor 44 during high-load events, or from the on-board charger 40 to the traction battery 12 during charging. These circuits are designed to handle voltages typically ranging from 400 volts to 800 volts in modern electric vehicles, with some systems pushing up to 1000 volts for improved efficiency.

[0037] Control and communication connections 52 allow the BMS 46 to monitor and control various aspects of the powertrain operation. For example, the control and communication connection 52 to the traction motor 44 carries speed and torque control signals, while the control and communication connection 52 to the traction battery 12 includes data from the thermal management system 48, individual cell voltages, temperatures, and other battery monitoring sensors. These communication lines can utilize automotive-grade protocols, such as Controller Area Network (CAN), or other protocols, such as automotive Ethernet.

[0038] Figure 4 This is a schematic diagram of a battery monitoring system 54 with an HV pump configuration. The system includes a traction battery 12 within the battery monitoring system 54, the traction battery having an HV positive terminal 14 and an HV negative terminal 16, with one or more arrays immersed in a cooling fluid 18. The battery monitoring system 54 includes an auxiliary battery 56 for powering auxiliary electronics such as the battery monitoring system 54. An HV pump 58 with associated circuitry 60 is powered by the traction battery 12, which is one of the HV loads 26, via a positive contactor switch 22 and a negative contactor switch 24 in a closed position. The HV pump 58 is configured to circulate the cooling fluid 18 over the array of traction batteries 12. The circuitry 60 is physically electrically connected to the array via the positive contactor switch 22 and the negative contactor switch 24. The circuitry 60 may include a shunt, which may be a resistor in physical contact with the cooling fluid 18, configured to detect current flow from the traction battery 12 through the cooling fluid 18 to the circuitry 60. Each array may include its own corresponding battery pack regulator module to measure the current flow through the cooling fluid 18 local to the array.

[0039] The circuit system 60 is configured to measure the voltage from the HV positive terminal 14 and the HV negative terminal 16 to chassis ground 30. The circuit system 60 may also include multiple electrodes positioned at different locations within the coolant 18 for comprehensive monitoring. The BMS 46 is coupled to the battery pack monitor module. The BMS 46 receives data from the circuit system 60 and can report contamination of the coolant 18 sufficient to form a closed loop 34. The BMS 46 correlates the detected current flow with vehicle diagnostic data to determine the level of contamination in the coolant 18. The BMS 46 can also determine, based on this correlation, whether an isolation fault is located inside or outside the traction battery 12. The BMS 46 is connected to the pump control unit via a communication connection 52.

[0040] Figure 5 This is a schematic diagram of a battery monitoring system 62 with an LV pump configuration. In the battery monitoring system 62, an LV pump 64 with associated circuitry 66 is configured to be powered by an auxiliary battery 56 via a power connection 50 to move cooling fluid 18 through the battery monitoring system 62. Circuitry 66 may include a shunt with a resistor having one terminal electrically connected to the auxiliary battery 56 and another terminal in contact with the cooling fluid 18. Circuitry 66 is configured to detect changes in the dielectric properties of the cooling fluid 18, including conductivity, dielectric constant, or impedance.

[0041] The BMS 46 is connected to the LV pump 64 and its circuitry 66. It receives data indicating the current flow through the cooling fluid 18 and can disable one or more arrays of the traction battery 12 if the detected contaminant level reaches a threshold. The BMS 46 can also adjust the charging rate of the traction battery 12 based on the detected contaminant level. As in the HV configuration, the BMS 46 is connected to the pump control unit via a communication connection 52. All components are referenced to chassis ground 30. This LV pump configuration allows for monitoring and management of the cooling fluid 18 when utilizing the vehicle's LV electrical system.

[0042] While representative embodiments have been described above, these embodiments are not intended to describe all possible forms of the invention. The wording used in this specification is descriptive rather than limiting, and it should be understood that various changes may be made without departing from the claimed subject matter. Furthermore, features of various embodiments may be combined to form other embodiments not explicitly described or shown, but within the scope of the claimed subject matter.

[0043] According to the present invention, an automotive battery system is provided, comprising: a traction battery; and a pump configured to circulate cooling fluid through the traction battery, the pump including a circuit system configured to detect current flow from the traction battery through the cooling fluid to the circuit system.

[0044] According to an embodiment, the pump is configured to be a high-pressure pump powered by the traction battery.

[0045] According to an embodiment, the invention is further characterized by an auxiliary battery, wherein the pump is a low-pressure pump configured to be powered by the auxiliary battery.

[0046] According to an embodiment, the circuit system includes a resistive shunt for measuring the current flow.

[0047] According to an embodiment, the circuit system includes a current sensor having both low-precision range capability and high-precision range capability.

[0048] According to an embodiment, the invention is further characterized by a battery management system configured to receive data from the circuit system and report fluid contamination based on the current flow.

[0049] According to an embodiment, the battery management system is also configured to classify the current flow as an associated contamination level of the cooling fluid.

[0050] According to the present invention, a vehicle electrical system is provided, comprising: a traction battery including one or more arrays immersed in a cooling fluid; and a pump configured to use power from the traction battery to circulate the cooling fluid through the one or more arrays, the pump including a circuit system configured to be physically electrically connected to the one or more arrays via a switch and to detect the current flow through the cooling fluid.

[0051] According to an embodiment, each of the arrays includes a battery pack monitor module configured to measure the current flow through the cooling fluid local to the array.

[0052] According to an embodiment, each of the battery pack monitor modules includes a shunt attached to an array of high-voltage terminals to detect voltage changes associated with the current flow through the cooling fluid.

[0053] According to an embodiment, the circuit system is also configured to measure the voltage from the positive and negative terminals to the chassis ground.

[0054] According to an embodiment, the invention is further characterized by a battery pack monitor module and a battery management system, the battery management system being connected to the battery pack monitor module and configured to correlate the current flow with diagnostic data.

[0055] According to an embodiment, the circuit system includes multiple electrodes positioned at different locations within the cooling fluid.

[0056] According to the present invention, an automotive system is provided, comprising: a housing; a traction battery and a cooling fluid contained within the housing; an auxiliary battery; and a pump configured to be powered by the auxiliary battery to move the cooling fluid through the housing, the pump including a resistor having a terminal electrically connected to the auxiliary battery and a terminal in contact with the cooling fluid.

[0057] According to an embodiment, the invention is further characterized by a battery management system configured to receive data indicating the current flow through the cooling fluid and to disable the traction battery based on the data.

[0058] According to an embodiment, the invention is further characterized by a battery management system configured to adjust the charging rate of the traction battery based on the data.

[0059] According to an embodiment, the invention is further characterized by a circuit that includes the resistor and is configured to detect changes in the dielectric properties of the cooling fluid, the dielectric properties including at least one of conductivity, dielectric constant, or impedance.

Claims

1. An automotive battery system, comprising: Traction battery; as well as A pump configured to circulate cooling fluid through the traction battery, the pump including a circuit system configured to detect current flow from the traction battery through the cooling fluid to the circuit system.

2. The automotive battery system of claim 1, wherein the pump is a high-voltage pump configured to be powered by the traction battery.

3. The automotive battery system of claim 1, further comprising an auxiliary battery, wherein the pump is a low-pressure pump configured to be powered by the auxiliary battery.

4. The automotive battery system of claim 1, wherein the circuit system includes a resistive shunt for measuring the current flow.

5. The automotive battery system of claim 1, further comprising a battery management system configured to receive data from the circuitry and report fluid contamination based on the current flow.

6. The automotive battery system of claim 5, wherein the battery management system is further configured to classify the current flow as an associated contamination level of the cooling fluid.

7. A vehicle electrical system comprising: A traction battery, the traction battery comprising one or more arrays immersed in a cooling fluid; as well as A pump configured to circulate cooling fluid through one or more arrays using power from the traction battery, the pump including a circuit system configured to be physically electrically connected to the one or more arrays via a switch and to detect the current flow through the cooling fluid.

8. The vehicle electrical system of claim 7, wherein each of the arrays includes a battery pack monitor module configured to measure the current flow through the cooling fluid local to the array.

9. The vehicle electrical system of claim 8, wherein each of the battery pack monitoring modules includes a shunt attached to an array of high-voltage terminals to detect voltage changes associated with the current flow through the cooling fluid.

10. The vehicle electrical system of claim 7, further comprising a battery pack monitor module and a battery management system, the battery management system being coupled to the battery pack monitor module and configured to correlate the current flow with diagnostic data.

11. The vehicle electrical system of claim 7, wherein the circuitry includes a plurality of electrodes located at different positions within the cooling fluid.

12. A vehicle system comprising: case; Traction battery and cooling fluid contained within the housing; Auxiliary battery; as well as A pump configured to be powered by the auxiliary battery to move the cooling fluid through the housing, the pump including a resistor having terminals electrically connected to the auxiliary battery and terminals in contact with the cooling fluid.

13. The vehicle system of claim 12, further comprising a battery management system configured to receive data indicating current flow through the cooling fluid and to disable the traction battery based on the data.

14. The vehicle system of claim 13, further comprising a battery management system configured to adjust the charging rate of the traction battery based on the data.

15. The automotive system of claim 12, further comprising a circuit including the resistor and configured to detect changes in the dielectric properties of the cooling fluid, the dielectric properties including at least one of conductivity, dielectric constant, or impedance.

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