Method for controlling a temperature in a thermal management system

Abstract

Method for controlling a temperature in a thermal management system (24) of a battery system (12) of a vehicle (10), wherein the temperature of at least one unit (14) of the battery system (12) is controlled to a first temperature setpoint when the battery system (12) is in a charging operation, and the temperature of the at least one unit (14) of the battery system (12) is controlled to a second temperature setpoint when the battery system (12) is in a driving operation, wherein the first temperature setpoint differs from the second temperature setpoint, wherein the first and / or the second temperature setpoint are adjusted depending on at least one state parameter, characterized in that one state parameter is an aging state parameter.

Description

State of the art

[0001] The invention relates to a method for regulating a temperature in a thermal management system of a battery system. The invention also relates to a battery system configured to implement the method and to an electrically powered vehicle having a corresponding battery system.

[0002] In the development of highly efficient drive concepts for low-emission vehicles, the concept of powertrain electrification in the form of various hybrid variants or purely electric drives is being pursued in particular. In purely electric vehicles (EVs), hybrid electric vehicles (HEVs), or externally chargeable hybrid vehicles (plug-in hybrid electric vehicles, PHIVs), electrical energy storage devices are key components for achieving the desired ranges. Electrical energy storage devices typically consist of battery systems with battery cells, also known as accumulator cells or galvanic cells.

[0003] Such battery systems are subject to stringent requirements in terms of energy density, charge / discharge efficiency, functional reliability, and service life. One factor that significantly influences the service life of such battery systems is the temperature at which the battery system is operated. For example, battery systems based on lithium-ion cells age significantly faster at temperatures above 40°C than at temperatures between 5 and 40°C. Therefore, it is common practice to equip battery systems with a thermal management system that maintains the temperature of the battery system within an optimal temperature range by heating or cooling, and keeps the temperature profile as constant as possible across multiple battery cells.

[0004] DE 10 2010 031 414 A1 describes a demand-based battery cooling system for electric or hybrid vehicles that takes dynamic influences and / or disturbances into account. This system uses an adjustable battery cooling system that includes cooling channels through which a coolant flows. A temperature setpoint in a single-loop control loop with characteristic-based setpoint generation serves as the actuator for the flow. The characteristic-based setpoint generation takes the ambient temperature or the respective driving mode into account.

[0005] DE 10 2012 208 980 A1 discloses a system for adjusting the battery temperature. This system, in particular, enables rapid charging by regulating the battery temperature accordingly. This allows warm air to be supplied to the battery in low-temperature conditions, for example, when the ambient temperature is below freezing, and cold air to be supplied in high-temperature conditions.

[0006] DE 10 2011 015 557 A1 describes a thermal management system for dissipating thermal energy from the secondary battery during operation.

[0007] DE 10 2011 108 646 A1 discloses a method for commissioning a cooling system for a motor vehicle battery. The cooling system can be operated both during charging and during driving. In both operating modes, the temperature in the battery pack is recorded and used to operate the cooling system.

[0008] From the document US 2013 / 0 166 119 A1, a temperature regulation system for a battery is known in which different temperatures of the battery are provided for the charging process and driving operation.

[0009] To increase the lifetime of a battery system, there is ongoing interest in improving the thermal management system of battery systems. Disclosure of the invention

[0010] According to the invention, the thermal management of battery systems is improved by the features of claims 1 and 8. For this purpose, a method for regulating a temperature in a thermal management system of a battery system of a vehicle and a corresponding battery system are proposed, wherein the temperature of at least one unit of the battery system is regulated to a first temperature setpoint when the battery system is in charging mode, and the temperature of the at least one unit of the battery system is regulated to a second temperature setpoint when the battery system is in driving mode, wherein the first temperature setpoint differs from the second temperature setpoint.

[0011] Charging mode refers to an operating state in which the battery is being charged, meaning the vehicle's battery is connected to an external power source and is supplied with electrical energy for charging. Driving mode refers to an operating state in which electrical energy from the battery is used to power the vehicle, particularly to drive the vehicle's electric motor. During driving, the battery is therefore discharged. This can also be referred to as discharging mode.

[0012] Furthermore, it is provided that the first and / or second temperature setpoint is adjusted depending on at least one state parameter. An aging state parameter is used as a state parameter. Furthermore, the first and / or second temperature setpoint can be adjusted depending on a state of health (SOH), which is provided, for example, by the battery management system. For example, the first and / or second temperature setpoint can be reduced when the SOH is low or increased when the SOH is high. The SOH is low or high if, in a current state of the battery, the target service life is exceeded or not met. The aging state of the battery can be determined, for example, based on the capacity of the battery and / or the battery cells.

[0013] The battery system is preferably part of a vehicle's electric drive system. A battery system refers to a system that comprises a battery with one or more battery cells that are monitored and controlled by a battery management system. Various functions can be implemented in the battery management system to monitor and control status parameters such as currents, voltages, or temperatures of the battery system to ensure the reliability, service life, and safety of the battery.

[0014] One function implemented in the battery management system concerns thermal management or temperature control within the battery system. In particular, the temperature of individual units of the battery system, such as the battery and its battery cells or battery modules in which several battery cells are combined, is controlled. Preferably, the temperature of the individual units of the battery system is controlled such that the temperature profile is essentially constant across multiple units of the battery system. Essentially constant here includes temperature deviations between individual units of + / - 10°C, preferably + / - 5°C.

[0015] In one implementation, it is detected whether the battery is in charging mode or driving mode. For example, a connection to an external power source can be detected while the battery is in charging mode. Alternatively, the ignition can be detected while the battery is in driving mode.

[0016] In a further implementation, the first and / or second temperature setpoints are provided as predefined values. Thus, a predefined value can be stored in memory for each of the first and / or second temperature setpoints, which can be assigned to a battery management system or another unit in the vehicle, such as a higher-level control unit.

[0017] Additionally or alternatively, the first and / or the second temperature setpoint can be adjusted depending on the ambient temperature as a further state parameter, which is provided, for example, by the battery management system or by another measuring device for the ambient temperature present in the vehicle.

[0018] In a further implementation, the first temperature setpoint, i.e. the temperature setpoint during charging, is lower than the second temperature setpoint, i.e. the temperature setpoint during driving. In a further implementation, the first temperature setpoint is at least 5°C, preferably at least 10°C, and particularly preferably at least 15°C lower than the second temperature setpoint. For lithium-ion battery cells, the first temperature setpoint can be in the range from 10 to 27°C, preferably in the range from 15 to 25°C. For example, the first temperature setpoint can be 20°C. It should be noted that the temperature setpoint is merely a specification and the temperature of the battery system unit can be within a range of + / - 5°C around the temperature setpoint. For lithium-ion battery cells, the second temperature setpoint can be in the range from 28 to 45°C, preferably in the range from 30 to 40°C.For example, the second temperature setpoint can be 35°C.

[0019] In another implementation, a control loop comprises recording a currently measured temperature of the battery system unit and regulating the temperature to a first or second temperature setpoint. The temperature of the battery system unit can be recorded using temperature sensors that measure the temperature of individual units, such as the battery cells or battery modules. In the control loop, the currently measured temperature represents the controlled variable. If the currently measured temperature deviates from the first or second temperature setpoint depending on the operating state, a control difference results, which leads to a change in a manipulated variable. A suitable manipulated variable, for example, is the cooling capacity or the heating capacity of a thermal unit.

[0020] In a further implementation, in order to control the currently measured temperature, the cooling capacity or the heating capacity of the thermal unit is adapted to a difference between the currently measured temperature and, depending on the operating state, the first or the second temperature setpoint.

[0021] In the battery system, the thermal unit is typically part of a battery cooling system that includes a temperature control fluid circuit with a pump and a battery cooling unit, in particular a cooling plate. The thermal unit can additionally be connected to another temperature control fluid circuit and act as a heat exchanger or as a heat transfer device between the two temperature control fluid circuits. For example, a cooling plate can be assigned to the battery module with multiple battery cells, which thermally connects the battery module to the battery cooling system via a heat conduction path from the cell base. The temperature control fluid circuit thus contains, in particular, the battery cooling unit, a pump, and a heat transfer device or a heat exchanger for providing the cooling capacity. A heating device can also be incorporated into the temperature control fluid circuit to provide appropriate heat output.A glycol-water mixture, for example, is suitable as a tempering fluid.

[0022] The method can be carried out as part of a computer program on a programmable computer device. The computer device can be, for example, a unit for implementing a battery management system, in particular a thermal management system, in a battery system of a vehicle. The computer program can be stored on a machine-readable storage medium, for example on a permanent or rewritable storage medium or in association with a computer device, or on a removable CD-ROM, DVD, Blu-ray disk, or USB stick. Additionally or alternatively, the computer program can be made available for download on a computer device, such as a server or a cloud server, for example via a data network such as the Internet or a communications connection, such as a telephone line or a wireless connection.

[0023] According to the invention, a battery system for regulating a temperature of a unit of the battery system is further proposed, which comprises the following components: a) at least one component for detecting charging or driving operation of the battery system, b) at least one component for providing a first temperature setpoint for charging operation and a second temperature setpoint for driving operation, wherein the first temperature setpoint differs from the second temperature setpoint, and c) at least one component for controlling the temperature of at least one unit of the battery system to the first temperature setpoint when the battery system is in charging mode and to the second temperature setpoint when the battery system is in cooling mode.

[0024] The battery system according to the invention is preferably designed and / or configured to carry out the methods described above. In the battery system, the functional components can be implemented in hardware or software on a programmable computer device, such as a control unit of the battery management system.

[0025] For example, the component for detecting charging or driving operation of the battery system can be designed as a sensor that detects a connection to a charging station or the switching on of an ignition.

[0026] The component for providing the first and / or second temperature setpoint may, for example, comprise a memory associated with the battery management system or another unit in the vehicle. If the first and / or second temperature setpoints are adjusted, the component for providing the temperature setpoints may be configured as a functional component or routine within a computer program executed on a programmable computer device.

[0027] The component for regulating the temperature of at least one unit of the battery system preferably comprises a control loop in which the currently measured temperature of the unit of the battery system is detected by temperature sensors and acts as a controlled variable in the control loop. Furthermore, the control loop comprises a component for determining the control deviation and a component for generating a control signal to adjust the manipulated variable, such as the cooling capacity or the heating capacity, of the thermal unit.

[0028] The invention also relates to an electrically powered vehicle with such a battery system. The battery system is preferably connected to a drive train of the electrically powered vehicle. Advantages of the invention

[0029] The invention enables the thermal management of battery systems to be optimally adapted to the requirements of charging and driving. Different temperature targets are selected for the two operating states, thereby reducing battery aging while simultaneously increasing the range.

[0030] In particular, the first temperature setpoint during charging can be selected to be lower than the second temperature setpoint during driving. This does mean that increased cooling capacity is required during charging because more electrical energy from the battery must be used for cooling. However, charging usually lasts longer than driving and therefore has a greater impact on the aging state of the battery cells and thus the battery system. The negative effects of high cell temperatures on the aging of the battery cells and thus the battery system can thus be drastically minimized by the low first temperature setpoint during charging. In addition, the higher temperature setpoint during driving compared to charging reduces the cooling capacity during driving, which simultaneously increases the vehicle's range because more electrical energy is available for the electric drive.

[0031] The two-part temperature setpoint for charging and driving thus works synergistically in such a way that not only the temperature-related aging of the battery cells or the battery system is reduced, but also the range of the vehicle is increased.

[0032] Additionally, the operating strategy can be adjusted with different temperature setpoints to take external influences into account. For example, a driver's driving behavior can be taken into account in such a way that the temperature setpoints are adjusted depending on the load. For example, the temperature setpoints can be raised during gentle use to reduce charging costs. This corresponds to a bonus for the driver for gentle driving. Conversely, the temperature setpoints can be lowered during heavy use to achieve the target service life.

[0033] Ambient conditions can also be incorporated into the operating strategy. For example, the temperature setpoint originally configured for the condition can be reduced in high ambient temperatures, resulting in a lower battery temperature after the charging process is complete. This, in turn, increases the battery's service life. Short description of the drawings

[0034] Further aspects and advantages of the invention will now be described in more detail with reference to the accompanying drawings.

[0035] They show: Fig. 1 a vehicle with a battery system in which thermal management is implemented, Fig. 2 in the form of a flow chart the operation of the battery system of the Fig. 1, and Fig. 3 schematically shows a control circuit for controlling the temperature in the battery system of the Fig. 1.

[0036] In the following description of the exemplary embodiments of the invention, identical or similar components and elements are designated by identical or similar reference numerals; in individual cases, a repeated description of these components or elements is omitted. The figures only schematically illustrate the subject matter of the invention. Embodiments of the invention

[0037] Fig. 1 shows a vehicle 10 with a battery system 12 in which thermal management is implemented.

[0038] The vehicle 10 can be a purely electric vehicle powered solely by an electric motor, or it can have an internal combustion engine in addition to the electric motor and be designed as a hybrid vehicle or a plug-in hybrid vehicle. To provide the electrical energy for the drive, the vehicle 10 is equipped with a battery system 12. The battery system 12 comprises a unit 14 with several battery cells. The battery cells can be connected in series or in parallel to form battery modules.

[0039] To control the temperature of the unit 14, for example, to control the temperature of battery cells or battery modules, the unit 14 is equipped with a battery cooling system 16. The battery cooling system 16 comprises at least one cooling plate 18, which is thermally connected to the battery cells or battery modules to be cooled. Furthermore, the battery cooling system 16 comprises a control circuit in which a temperature control fluid is conducted, for example, a water-glycol mixture. An additional part of the control circuit is a thermal unit 20, which serves as a heat exchanger for providing cooling power. In addition to the components for cooling the unit 14, the battery cooling system 16 can also comprise a heating device (not shown), which enables heating operation in addition to cooling operation.

[0040] To control and monitor the unit 14, the battery system 12 further comprises a battery management system 22, in which various functions for monitoring and controlling the status parameters of the unit 14 are implemented. One implementation concerns thermal management, which monitors and regulates the temperature of the unit 14 and, in particular, the battery cells.

[0041] For this purpose, the battery management system 22 is, along with other Fig. 1, functional units not shown are equipped with a thermal management system 24. To regulate the temperature, various communication connections are provided between the battery management system 22 or the thermal management system 24 and other components. Thus, the battery management system 22 or the thermal management system 24 has an interface 30 for exchanging data via a first communication channel 26 with an interface 28 of the unit 14. In particular, status parameters, such as temperatures, voltages, or currents, of the battery cells are transmitted to the battery management system 22 or the thermal management system 24 via the communication channel 26. In addition, the battery management system 22 or the thermal management system 24 comprises an interface 36, and the thermal unit 20 comprises an interface 38, between which data can be exchanged via a second communication channel 34.The first and second communication channels 26, 34 can be configured as a data bus, for example, as a serial data bus (Serial Peripheral Interface, SPI) or as a CAN bus (Control Area Network Bus). Furthermore, an outside temperature sensor 58 can be connected to the battery management system 22 or the thermal management system 24 to provide an ambient temperature.

[0042] In order to detect whether the battery system 12 is in charging mode or driving mode, the battery management system 22 or the thermal management system 24 is connected to a sensor 40, which detects, for example, the switching on of an ignition and transmits this information to the battery management system 22 or the thermal management system 24 via a communication channel 42. In order to detect whether the battery system 12 is in charging mode, the battery management system 22 or the thermal management system 24 is further connected to a charging element 44, which detects a connection to an external power source 48 and transmits this information to the battery management system 22 or the thermal management system 24 via a communication channel 46. If the battery system 12 is in charging mode, electrical energy is transmitted from the external power source 48 to the vehicle 10, and in particular to the unit 14, via an electrical line 50.The charging process is controlled by the battery management system 22, which activates an electrical connection 52 between the external power source 48 and the unit 14. Additionally, a communication channel 45 for data transmission can be established between the battery management system 22 and the external power source 48.

[0043] In Fig. 2 is a flow chart showing the operation of the battery system 12 from Fig. 1 shown.

[0044] In a first step 100, the thermal management system 24 is initialized by detecting the connection to the external power source 48 or switching on of an ignition via the sensor 40.

[0045] In a second step 102, the acquired data is transmitted to the battery management system 22 or the thermal management system 24, and the operating state of the battery system 12 is determined. If a connection to the external power source 48 was detected in the second step 102, the battery system 12 is in charging mode. If the ignition switch-on was detected in the second step 102, the battery system 12 is in driving mode.

[0046] Depending on the determined operating state, the temperature setpoint is determined in a third step 104. If charging mode was determined in the second step 102, a first temperature setpoint is determined in a fourth step 106. If it was determined in the second step 102 that the battery system 12 is in driving mode, a second temperature setpoint is determined in a fifth step 108. The first and second temperature setpoints can be stored as predefined values ​​in a memory associated with the battery management system 22 or the thermal management system 24.

[0047] Alternatively, as in Fig. 2, the first and second temperature setpoints are adjusted. For this purpose, state parameters can be provided in a sixth and seventh step 110, 112, which are taken into account in the fourth or fifth steps 106, 108 when determining the first and / or second temperature setpoint.

[0048] In particular, the aging state of the unit 14 based on the SOH parameter as well as the ambient temperature are taken into account. If the SOH is low, for example, this indicates high stress on the unit 14. This can be at least partially compensated for by reducing the first and / or the second temperature setpoint compared to the setpoints for a normal aging state. Conversely, the first and / or the second temperature setpoint can be increased if the SOH parameter is high, thus indicating gentle stress on the unit 14. If the ambient temperature is low, for example less than 10°C, the first and / or the second temperature setpoint can be reduced by approximately 20°C compared to the setpoints for a normal ambient temperature.

[0049] After setting the first and / or second temperature setpoints in the fourth or fifth steps 106, 108, the temperature of the battery, or of a unit 14, such as one or more battery cells or battery modules, is controlled in the eighth step 114. In charging mode, the temperature of the unit 14 is controlled to the first temperature setpoint in a ninth step 116. In driving mode, the temperature of the unit 14 is controlled to a second temperature setpoint in a tenth step 118. For this purpose, a control circuit 200 is implemented, which Fig. 3 is shown in more detail.

[0050] Fig. 3 shows a control circuit 200 for controlling a temperature in a battery system 12.

[0051] Depending on the operating state, the first or second temperature setpoint represents a setpoint 202 of the control loop 200. To control a currently measured temperature 204 of the unit 14, a difference 206 is first calculated between the currently measured temperature 204 and the first or second temperature setpoint. This results in a control deviation 208, which is counteracted by a controller 210. For this purpose, the controller 210 changes a manipulated variable 212, which in the battery cooling system 16 can be, for example, the cooling output. Thus, depending on the control deviation 208, the cooling output can be increased or decreased. If disturbances 214, such as heat generation in the unit 14, cause changes in the currently measured temperature as controlled variable 204, which in turn triggers a deviation from the first or second temperature setpoint, the control loop 200 is run through again.

[0052] The invention is not limited to the embodiments described here and the aspects highlighted therein. Rather, numerous modifications are possible within the scope of the claims, which are within the scope of one skilled in the art.

Claims

[1] Method for regulating a temperature in a thermal management system (24) of a battery system (12) of a vehicle (10), wherein the temperature of at least one unit (14) of the battery system (12) is regulated to a first temperature setpoint when the battery system (12) is in charging mode, and the temperature of the at least one unit (14) of the battery system (12) is regulated to a second temperature setpoint when the battery system (12) is in driving mode, wherein the first temperature setpoint differs from the second temperature setpoint, wherein the first and / or the second temperature setpoint are adapted as a function of at least one state parameter, characterized by that a state parameter is an aging state parameter. [2] The method of claim 1, wherein the unit (14) is in charging mode when a connection to an external power source (48) is detected or wherein the unit (14) is in driving mode when switching on an ignition is detected. [3] The method of claim 2, wherein an additional condition parameter is a health condition or an ambient temperature. [4] Method according to one of claims 1 to 3, wherein the first temperature setpoint is smaller than the second temperature setpoint. [5] Method according to one of claims 1 to 4, wherein the first temperature setpoint is at least 5°C lower than the second temperature setpoint. [6] Method according to one of claims 1 to 5, wherein a control circuit (200) comprises detecting a currently measured temperature (204) of the unit (14) of the battery system (12) and controlling the currently measured temperature (204) to the first or second temperature setpoint. [7] Method according to claim 6, wherein, in order to control the currently measured temperature (204), a cooling capacity or a heating capacity of a thermal unit (20) is adapted to a control deviation (208) between the currently measured temperature (204) and the first or the second temperature setpoint. [8] Battery system (12) for controlling a temperature of a unit (14) of the battery system (12) according to one of the methods 1 to 7, comprising the following components: a) at least one component for detecting a charging operation or driving operation of the battery system (12), b) at least one component for providing a first temperature setpoint for charging operation and a second temperature setpoint for driving operation, wherein the first temperature setpoint and the second temperature setpoint differ, and c) at least one component for regulating the temperature of at least one unit (14) of the battery system (12) to the first temperature setpoint when the battery system (12) is in charging mode and to the second temperature setpoint when the battery system (12) is in driving mode, characterized by that the at least one component for providing a first and / or second temperature setpoint adapts the first and / or second temperature setpoint depending on at least one state parameter, wherein a state parameter is an aging state parameter. [9] Electrically powered vehicle (10) with a battery system (12) according to claim 8.

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