Method for monitoring a cooling device for cooling a traction battery

Abstract

Method for monitoring a cooling device for cooling a traction battery, comprising the steps: Determining a reference value (VW) that is representative of the cooling power absorbed by the battery (P) K ) is, Determining a reference value (RW) that is representative of the cooling capacity (B) provided by the cooling device K ) is, Comparing the comparative value (VW) with the reference value (RW), Generating an error signal (FS) when there is a difference between the comparison value (VW) and the reference value (RW), and Sending an error message in response to the error signal (FS), where, to determine the reference value (VW), a battery temperature (BT) is used. n ) representative value and one for an ambient temperature (UT n ) representative value is recorded and evaluated, where, by evaluating the representative value for the battery temperature (BT) n ) and the representative value for the ambient temperature (UT n ) a temperature difference (ΔT) is determined, and the comparative value (VW) is determined using the temperature difference (ΔT), and where, by evaluating a battery constant (λs) for the battery and a representative value for a battery heat flux (ΔTλs) of the traction battery is determined from the temperature difference (ΔT), and the comparison value (VW) is determined using the representative value for the battery heat flux (ΔTλs).

Description

[0001] The invention relates to a method for monitoring a cooling device for cooling a traction battery.

[0002] A traction battery (also known as a traction accumulator, drive battery, or cycle battery) is an energy storage device used to power the drive system of an electric vehicle. They consist of several interconnected battery cells or cell blocks.

[0003] These types of traction batteries are cooled during operation by a cooling system to protect them from overheating due to heat generated during charging and discharging processes. The cooling system circulates a coolant in a coolant circuit. To verify the functionality of the cooling system, it is known to use flow sensors to detect whether sufficient coolant is circulating to adequately cool the traction battery. However, these flow sensors require limited installation space. Furthermore, the installation and connection of the flow sensors increase manufacturing complexity and thus production costs.

[0004] From DE 10 2012 201 609 A1 a control device for the control of a cooling circuit for temperature control of a battery system with more than one heating and / or cooling element is known.

[0005] From DE 11 2007 002 846 T5 a device and a method for electrical equipment are known.

[0006] The object of the invention is therefore to show ways in which monitoring of a cooling device for cooling a traction battery can be achieved with less manufacturing effort and reduced installation space requirements.

[0007] The object of the invention is achieved by a method for monitoring a cooling device for cooling a traction battery, comprising the steps of: Determining a reference value that is representative of the cooling power absorbed by the traction battery, Determining a reference value that is representative of the cooling capacity provided by the cooling device,

[0008] Comparing the comparison value with the reference value,

[0009] Generating an error signal when there is a difference between the comparison value and the reference value, and issuing an error message in response to the error signal. where, to determine the reference value, a value representative of a battery temperature and a value representative of an ambient temperature are recorded and evaluated, wherein a temperature difference is determined by evaluating the representative value for the battery temperature and the representative value for the ambient temperature, and the comparison value is determined using the temperature difference, and wherein, by evaluating a battery constant for the battery and the temperature difference, a representative value for a battery heat flux of the traction battery is determined, and the comparison value is determined using the representative value for the battery heat flux.

[0010] Thus, the invention departs from directly measuring coolant transport in a coolant circuit of the cooling device. Instead, it proposes to infer a fault in the coolant circuit by comparing the absorbed and supplied cooling power, or representative values ​​thereof, thereby generating an error signal. In other words, a model of the thermal behavior of the traction battery is used to determine the absorbed cooling power, or a representative value thereof, which is then compared with the supplied cooling power, which is easier to measure. The supplied cooling power can be determined, for example, by measuring the power consumption of a cooling compressor in the cooling device. This eliminates the need for the limited installation space of flow sensors and also avoids the need for their installation and connection.

[0011] By determining the reference value, a value representative of the battery temperature and a value representative of the ambient temperature are recorded and evaluated. This allows the battery temperature to be measured using temperature sensors already intended for battery temperature measurement, while the ambient temperature can be measured using a temperature sensor designed for measuring the outside or air temperature. Thus, existing temperature sensors are used, eliminating the need for additional components.

[0012] By determining a temperature difference from the representative value for the battery temperature and the representative value for the ambient temperature, and by determining the comparison value using the temperature difference, the battery temperature and the ambient temperature are linked in an easy-to-process way.

[0013] By determining a representative value for the traction battery's heat flow using a battery constant and the temperature difference, and by determining the comparison value using the representative value for the battery's heat flow, a heat flow resulting from the traction battery's design and the temperature difference is determined directly or indirectly, thus increasing the accuracy of the determination of the absorbed cooling power.

[0014] Preferably, the reference value is determined using a representative value for the thermal energy of the traction battery. This allows the energy state of the traction battery to be determined and taken into account. In this way, the accuracy of determining the absorbed cooling power can be further increased.

[0015] Preferably, the reference value is determined at intervals, using a representative value for the thermal energy of the traction battery in one interval and a second representative value for the thermal energy of the traction battery in a previous interval. The procedure is then repeated at a predetermined interval. The period of the interval can range from one second to five minutes to account for the thermal inertia of the traction battery. By using the representative value for the thermal energy in one interval, i.e., the energy state of the traction battery, and the representative value for the thermal energy in a previous interval, changes in the energy state of the traction battery can be easily detected and accounted for.The thermal energy of the traction battery can be determined by evaluating the battery temperature and the specific heat capacity of the traction battery.

[0016] Furthermore, the invention includes a computer program product comprising program modules configured to carry out such a method, a device for monitoring a cooling device for cooling a traction battery, and a motor vehicle with such a device for monitoring a cooling device for cooling a traction battery.

[0017] The invention will now be explained with reference to a drawing. The drawing shows: Fig. 1 in schematic representation an embodiment of a device for monitoring a cooling device for cooling a traction battery, and Fig. 2 in schematic representation a process of an embodiment of a method according to the invention.

[0018] It will initially be on Fig. 1 referenced.

[0019] The illustration shows a device 2 for monitoring a cooling device for cooling a traction battery, such as a high-voltage storage unit of an electric vehicle. This can be a fully electric vehicle or a hybrid vehicle.

[0020] In the present embodiment, the device 2 comprises a comparison value determination unit 4, a reference value determination unit 6, a comparison unit 8, and an output unit 10. The comparison value determination unit 4, the reference value determination unit 6, the comparison unit 8, and / or the output unit 10 may include hardware and / or software components for performing the tasks described below.

[0021] The comparative value determination device 4 is designed to determine a value for a battery temperature BT within a predetermined interval n with a period N. n representative value and one for an ambient temperature UT n to read and evaluate a representative value. The battery temperature BT n can be used with a battery temperature sensor (BT) n The intended temperature sensor will detect the ambient temperature (UT). n This can be detected using a temperature sensor to measure the outside or air temperature. The period N of the interval n can range from one second to five minutes to account for the thermal inertia of the traction battery. In the present embodiment, the period N is one minute.

[0022] The representative value for battery temperature BT nand the representative value for the ambient temperature UT n For example, data can be transmitted from the respective temperature sensors to the comparative value determination device 4 via a CAN bus.

[0023] In the present embodiment, the comparative value determination device 4 is designed to determine the representative value for the battery temperature BT. n and the representative value for the ambient temperature UT n to use in order to determine a temperature difference ΔT.

[0024] Furthermore, in the present embodiment, the comparative value determination device 4 is configured to determine a battery heat flux ΔTλs of the traction battery. For this purpose, the comparative value determination device 4 uses the determined temperature difference ΔT and a battery constant λs of the traction battery, which describes its thermal conductivity, and calculates the product of these two values.

[0025] Furthermore, as will be described in detail later, the comparative value determination device 4 is designed to determine the comparative value VW in the interval n. In addition, a representative value for the thermal energy E is determined in each interval n. Bat, n the traction battery is determined, i.e., a representative value for the thermal energy E is determined. Bat, n the traction battery for a current interval n and a second representative value for the thermal energy E Bat, n-1 the traction battery was used for a pre-interval n-1.

[0026] The thermal energy E Bat, n The traction battery for the current interval n is determined by evaluating the battery temperature BT. n for the current interval n and the specific heat capacity of the traction battery, while the thermal energy E Bat, n-1The traction battery for the pre-interval n-1 is determined by evaluating the battery temperature BT. n-1 for the pre-interval n-1 and also the specific heat capacity of the traction battery.

[0027] Finally, in the present embodiment, the comparative value determination device 4 is designed to determine a heat energy loss P V to take into account the traction battery that occurs in the interval n.

[0028] Thus, in the present embodiment, the comparative value determination device 4 evaluates the representative value for the battery temperature BT. n , the representative value for the ambient temperature UT n , the battery constant λs, the heat energy loss P V , a representative value for thermal energy E Bat, n the traction battery in the current interval n and a second representative value E Bat, n-1The thermal energy of the traction battery is used in a preliminary interval n-1 to determine the reference value VW. The reference value VW is representative of the absorbed cooling power P. k .

[0029] The absorbed cooling power P k The heat energy balance of the traction battery is determined in discrete-time form using the following equation: EBat,n=EBat,n−1+PVN+ΔTλsN−PKN

[0030] This stands for E Bat, n for a representative value of the thermal energy of the traction battery in the current interval n, E Bat, n-1 for a representative value of the thermal energy of the traction battery in the pre-interval n-1, P V N for the heat energy loss in the interval n and ΔTλsN battery heat flow in the interval n, each with period N.

[0031] Solved for P kühlThe equation for the heat energy balance in discrete-time form is: PK=1N(EBat,n−1−EBat,n+PV+ΔTλsN)

[0032] The reference value determination device 6 is designed to determine the reference value RW, which is representative of the cooling capacity B provided by the cooling device. K For example, the reference value RW can be determined by recording and determining the power consumption LA of a cooling compressor in the cooling device.

[0033] The comparator 8 is designed to compare the comparison value VW with the reference value RW and generates a control signal AS when the comparison value VW is too high, e.g. due to an excessively high battery temperature BT. n , greater than the reference value RW.

[0034] The output device 10 is designed to generate and output the error signal FS upon receipt of the control signal AS, e.g. to feed it into the CAN bus.

[0035] It will now be further referred to as Fig. 2 the operation of device 2 for monitoring a cooling device for cooling a traction battery is explained.

[0036] In one step, 100 are used to determine a representative value for the battery temperature BT. n and a representative value for the ambient temperature UT n The temperature difference ΔT was read in by the comparative value determination device 4 and determined.

[0037] In step 200, the battery constant λs is read from the comparison value determination device 4 and multiplied by the temperature difference ΔT to determine the battery heat flux ΔTλs.

[0038] In step 300, the comparative value determination device 4 determines a representative value for a thermal energy E. Bat, n the traction battery in the interval n and the second representative value E Bat, n-1for thermal energy of the traction battery in the pre-interval I n-1 as well as the heat energy loss P V The data was read in and the VW reference value was determined, which is representative of the cooling power P absorbed by the traction battery. K is

[0039] In step 400, the reference value determination device 6, for example, records a power consumption LA of a cooling compressor of the cooling device and determines the reference value RW by evaluating the power consumption.

[0040] In step 500, the comparator unit 8 compares the comparison value VE and the reference value RW. If the comparison value VW is greater than the reference value RW, the comparator unit 8 generates the control signal AS, whereupon the output unit 10 generates the error signal FS and feeds it, for example, into the CAN bus in the form of an error message.

[0041] Furthermore, the procedure is repeated in intervals n with a predetermined period N. In particular, the respective thermal energy of the traction battery E is measured in each interval n, n-1. Bat, n , E Bat, n-1 determined and the difference between these values ​​was calculated to take into account changes in the thermal energy balance of the traction battery.

[0042] In contrast to the present embodiment, the sequence of steps 100 to 500 can also be different, or steps 100 to 500 can be performed in parallel, i.e., simultaneously. For example, the method can begin with step 400, followed by steps 100 to 300, and then end with step 500, or steps 300 and 400 can be performed simultaneously.

[0043] This makes it possible to conclude that there is a fault in the coolant circuit by comparing the recorded and the provided cooling capacity, or representative values ​​thereof, without measuring the coolant flow using flow sensors. Reference symbol list 2 Device 4 Comparative value determination device 6 Reference value determination device 8 Comparative Institution 10 Output device 100 steps 200 steps 300 steps 400 steps 500 steps AS control signal B K provided cooling capacity BT n Battery temperature in interval n E Bat, n thermal energy of the battery in the interval n E Bat, n-1 thermal energy of the battery in the pre-interval n-1 FS error signal n interval n-1 preinterval N period LA power consumption P K absorbed cooling power P V Heat energy loss RW Reference Value UT n Ambient temperature in interval n VW comparative value ΔT temperature difference ΔTλs battery heat flow λs battery constant

Claims

[1] Method for monitoring a cooling device for cooling a traction battery, comprising the steps: Determining a reference value (VW) that is representative of the cooling power absorbed by the battery (P) K ) is, Determining a reference value (RW) that is representative of the cooling capacity (B) provided by the cooling device K ) is, Comparing the comparative value (VW) with the reference value (RW), Generating an error signal (FS) when there is a difference between the comparison value (VW) and the reference value (RW), and Sending an error message in response to the error signal (FS), where, to determine the reference value (VW), a battery temperature (BT) is used. n ) representative value and one for an ambient temperature (UT n ) representative value is recorded and evaluated, where, by evaluating the representative value for the battery temperature (BT) n ) and the representative value for the ambient temperature (UT n ) a temperature difference (ΔT) is determined, and the comparative value (VW) is determined using the temperature difference (ΔT), and where, by evaluating a battery constant (λs) for the battery and a representative value for a battery heat flux (ΔTλs) of the traction battery is determined from the temperature difference (ΔT), and the comparison value (VW) is determined using the representative value for the battery heat flux (ΔTλs). [2] Method according to claim 1, wherein the comparison value (VW) is determined using a representative value for thermal energy of the battery (E). Bat, n ) is determined. [3] Method according to claim 2, wherein the reference value (VW) is determined in intervals (n, n-1), and the reference value (VW) is determined using a representative value for a thermal energy (E). Bat, n ) of the traction battery in an interval (n) and from a second representative value for a thermal energy of the battery (E Bat, n-1 ) is determined in a preliminary interval (n-1). [4] Computer program product comprising program modules configured to perform a method according to any one of claims 1 to 3. [5] Device (2) for monitoring a cooling device for cooling a traction battery, with a comparative value determination device (4) for determining a comparative value (VW) that is representative of the cooling power absorbed by the battery (P) K ) is, a reference value determination device (6) for determining a reference value (RW) that is representative of the cooling capacity provided by the cooling device (B) K ) is, a comparison device (8) for comparing the comparison value (VW) with the reference value (RW), and an output device (10) for generating and outputting an error signal (FS) when there is a difference between the comparison value (VW) and the reference value (RW) and for issuing an error message in response to the error signal (FS), wherein the comparative value determination device (4) is configured to determine a battery temperature (BT n ) representative value and one for an ambient temperature (UT n ) to capture and evaluate representative values, wherein the comparison value determination device (4) is designed to evaluate the representative value for the battery temperature (BT) n) and the representative value for the ambient temperature (UT n ) to determine a temperature difference (ΔT), and to determine the reference value (VW) using the temperature difference (ΔT), and wherein the comparison value determination device (4) is configured to determine a representative value for a battery heat flux (ΔTλs) of the traction battery by evaluating a battery constant (λs) for the traction battery and the temperature difference (ΔT), and to determine the comparison value (VW) using the representative value for the battery heat flux (ΔTλs). [6] Device (2) according to claim 5, wherein the comparison value determination device (4) is configured to determine the comparison value (VW) using a representative value for thermal energy of the battery (E). Bat ) to determine. [7] Device (2) according to claim 6, wherein the comparison value determination device (4) is configured to determine the comparison value (VW) in intervals (n, n-11) and to determine the comparison value (VW) using a representative value for a thermal energy (E) Bat, n ) of the traction battery in an interval (n) and from a second representative value for a thermal energy (E Bat, n-1 ) of the traction battery in a pre-interval (n-1). [8] Motor vehicle with a device (2) according to any one of claims 5 to 7.

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