DE102016215425A1 - Method for monitoring a cooling device for cooling a traction battery - Google Patents

Abstract

The invention relates to a method for monitoring a cooling device for cooling a traction battery, comprising the steps of: determining a comparison value (VW) that is representative of the cooling power (P) received by the battery, determining a reference value (RW) that is representative of the cooling power (B) provided by the cooling device is, comparing the comparison 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 canceling an error message to the error signal (FS).

Description

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

A traction battery (also referred to as traction battery, traction battery or cycle battery) is an energy storage that is used to power a drive of an electric vehicle. They consist of several accumulator cells or cell blocks connected together.

Such traction batteries are cooled in operation by means of a cooling device to protect them from overheating by heat generated due to conversion processes in the traction battery during charging or discharging. During operation, the cooling device circulates a coolant in a coolant circuit. In order to check the functionality of the cooling device, it is known to detect by means of flow sensors whether sufficient coolant is circulated in order to cool the traction battery sufficiently. However, the flow sensors take up scarce space. Furthermore, the assembly and the connection of the flow sensors increases the production costs and thus the production costs.

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

• Bestimmen eines Vergleichswertes, der repräsentativ für die von der Traktionsbatterie aufgenommene Kühlleistung ist,
• Bestimmen eines Referenzwertes, der repräsentativ für die von der Kühlvorrichtung bereitgestellte Kühlleistung ist,
• Vergleichen des Vergleichswertes mit dem Referenzwert,
• Erzeugen eines Fehlersignals, wenn eine Differenz zwischen dem Vergleichswert und dem Referenzwert vorliegt und Absetzen einer Fehlermeldung auf das Fehlersignal hin.

The object of the invention is achieved by a method for monitoring a cooling device for cooling a traction battery, comprising the steps:

• Determining a comparison value that is representative of the cooling power consumed by the traction battery,
• Determining a reference value representative of the cooling power provided by the cooling device,
• Comparing the comparison value with the reference value,
• Generating an error signal when there is a difference between the comparison value and the reference value and issuing an error message to the error signal.

Thus, the invention turns away from directly measuring a coolant transport in a coolant circuit purchase of the cooling device, but instead proposes to conclude by comparing the recorded and the provided cooling capacity or values representative thereof to a fault in the coolant circuit, whereupon a Error signal is generated. In other words, a model of the thermal behavior of the traction battery is used to determine the absorbed cooling capacity or a value representative of this, which is then compared with a cooling performance provided with greater ease of measurement. The provided cooling capacity may e.g. be determined by detecting a power consumption of a cooling compressor of the cooling device. So no short space of flow sensors is required and it is also no installation and connection of flow sensors needed.

It is preferably provided that a value representative of a battery temperature and a value representative of an ambient temperature are detected and evaluated in order to determine the comparison value. The battery temperature can be detected with temperature sensors already provided for detecting the battery temperature, while the ambient temperature can be detected with a temperature sensor for detecting the outside or air temperature. Thus, existing temperature sensors are used anyway. It thus eliminates a mounting of other components.

Preferably, it is provided that 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. Thus, the battery temperature and the ambient temperature are linked together in an easy-to-process manner.

It is preferably provided that a representative value for a battery heat flow of the traction battery is determined by evaluating a battery constant for the traction battery and the temperature difference, and the comparison value is determined using the representative value for the battery heat flow. It is thus due to the structural design of the traction battery and the Temperature difference adjusting heat flow directly or indirectly determined and thus increases the accuracy of the determination of the absorbed cooling capacity.

It is preferably provided that the comparison value is determined using a representative value for a thermal energy of the traction battery. Thus, the energetic state of the traction battery is determined and taken into account. Thus, the accuracy of the determination of the absorbed cooling capacity can be increased again.

It is preferably provided that the comparison value is determined at intervals, and the comparison value is determined using a representative value for a thermal energy of the traction battery in one interval and a second representative value for a thermal energy of the traction battery in a pre-interval. Thus, the process is repeated at a predetermined interval. The period of the interval may be in the range of one second to five minutes so as to account for the thermal inertia of the traction battery. By taking the representative value for the thermal energy in an interval, i. the energetic state of the traction battery, and taking the representative value for the thermal energy in a pre-interval can be detected and taken into account in a simple manner changes in the energetic state of the traction battery. In this case, the thermal energy of the traction battery can be determined by evaluating the battery temperature and the specific heat capacity of the traction battery.

The invention also relates to a computer program product comprising program modules adapted to carry out such a method, a device for monitoring a cooling device for cooling a traction battery, and a motor vehicle having such a device for monitoring a cooling device for cooling a traction battery.

• 1 in schematischer Darstellung ein Ausführungsbeispiel einer Vorrichtung zur Überwachung einer Kühlvorrichtung zur Kühlung einer Traktionsbatterie, und
• 2 in schematischer Darstellung einen Ablauf eines Ausführungsbeispiels eines erfindungsgemäßen Verfahrens.

The invention will now be explained with reference to a drawing. Show it:

• 1 a schematic representation of an embodiment of a device for monitoring a cooling device for cooling a traction battery, and
• 2 a schematic representation of a sequence of an embodiment of a method according to the invention.

It is going on first 1 Referenced.

Shown is a device 2 for monitoring a cooling device for cooling a traction battery, such as a high-voltage accumulator of a motor vehicle with electric drive. It may be a fully electric motor vehicle or a motor vehicle with hybrid drive.

The device 2 has in the present embodiment, a comparison value determination device 4 , a reference value determination device 6 , a comparison device 8th and an output device 10 on. In this case, the comparison value determination device 4 , the reference value determination device 6 , the comparison device 8th and / or the output device 10 Have hardware and / or software components for performing the tasks described below.

The comparison value determination device 4 is designed to be within a predetermined interval n with a period duration N one for a battery temperature BT _n representative value and one for an ambient temperature UT _n to read and evaluate the representative value. The battery temperature BT _n can use a to record the battery temperature BT _n provided temperature sensor can be detected while the ambient temperature UT _n can be detected with a temperature sensor for detecting the outside or air temperature. The period duration N of the interval n may be in the range of one second to five minutes to accommodate the thermal inertia of the traction battery. In the present embodiment, the period is N a minute.

The representative value for the battery temperature BT _n and the representative value for the ambient temperature UT _n can eg by means of a CAN bus from the respective temperature sensors to the comparison value determination device 4 be transmitted.

The comparison value determination device 4 is formed in the present embodiment, the representative value for the battery temperature BT _n and the representative value for the ambient temperature UT _n to use a temperature difference .DELTA.T to determine.

Further, the comparison value determination means 4 formed in the present embodiment, a battery heat flow ΔTλs to determine the traction battery. For this purpose, the comparative value determination device uses 4 the specific temperature difference .DELTA.T and a battery constant .lambda..sub.s the traction battery, which describes their thermal conductivity and forms the product of these two values.

Furthermore, as will be described later in detail, the comparison value determining means 4 adapted to the comparison value VW in the interval n to determine. Furthermore, in every interval n a representative value for the thermal energy E _{Bat, n} of the traction battery, ie, it becomes a representative value for the thermal energy E _{Bat, n} the traction battery for a current interval n determined and a second representative value for the thermal energy E _{Bat, n-1} the traction battery for a pre-interval n-1 used.

The thermal energy E _{Bat, n} the traction battery for the current interval n is determined by evaluation of the battery temperature BT _n for the current interval n and determines the specific heat capacity of the traction battery, while the thermal energy E _{Bat, n-1} the 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 is determined.

Finally, in the present embodiment, the comparison value determination device 4 adapted to account for a heat energy loss P _{v of} the traction battery, in the interval n occurs.

Thus, the comparison value determination means evaluates 4 in the present embodiment, the representative value for the battery temperature BT _n , the representative value for the ambient temperature UT _n , the battery constant .lambda..sub.s , the heat energy loss Pv, a representative value for the thermal energy E _Bat , _n the traction battery in the current interval n and a second representative value E _{Bat, n-1} for the thermal energy of the traction battery in a pre-interval n-1 off to the comparison value VW to determine. The comparison value VW is representative of the absorbed cooling power P _k .

The absorbed cooling power P _k is determined using the following equation in discrete-time form for the heat energy balance of the traction battery: $$e_{Bat.n}=e_{Bat.n-1}+P_{V}N+\mathrm{\Delta }{\rm T}\lambda sN-P_{K}N$$

It says 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 traction battery thermal energy in the pre-interval n-1 , PvN for the heat energy loss in the interval n and ΔTλsN battery heat flux in the interval n , each with the period duration N ,

Solved after P _cool , the equation for the heat energy balance in discrete-time form is: $$P_K=\frac{1}{N}\left(e_{Bat.n-1}-e_{Bat.n}+P_V\mathrm{+\; \Delta }{\rm T}\lambda sN\right)$$

The reference value determination device 6 is for determining the reference value RW representative of the cooling power provided by the cooling device B _K is. For example, the reference value RW be determined by a power consumption LA a cooling compressor of the cooling device is detected and determined.

The comparison device 8th is for comparing the comparison value VW with the reference value RW trained and generates a drive signal AS if the comparison value VW , eg due to a too high battery temperature BT _n , greater than the reference value RW is.

The output device 10 is designed to receive the drive signal AS out the error signal FS to generate and output, eg to feed into the CAN bus.

It will now be with additional reference to the 2 the operation of the device 2 for monitoring a cooling device for cooling a traction battery explained.

In one step 100 become a representative value for the battery temperature BT _n and a representative value for the ambient temperature UT _n from the comparison value determination device 4 read in and the temperature difference .DELTA.T certainly.

In one step 200 is determined by the comparison value determination device 4 the battery constant .lambda..sub.s read in and with the temperature difference .DELTA.T multiplied by the battery heat current ΔTλs to determine.

In one step 300 are determined by the comparison value determination device 4 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-1} for a thermal energy of the traction battery in the pre-interval I _n-1 and the heat energy loss Pv read in and the comparison value VW which is representative of the power absorbed by the traction battery cooling power P _K is

In one step 400 is from the reference value determination device 6 eg a power consumption LA a cooling compressor of the cooling device detected and by evaluating the power consumption of the reference value RW certainly.

In one step 500 become the reference value VE and the reference value RW from the comparator 8th compared. If the comparison value VW greater than the reference value RW is generated the comparator 8th the drive signal AS , whereupon the output device 10 the error signal FS generated and fed in the form of an error message, for example, in the CAN bus.

Furthermore, the procedure is at intervals n with the predetermined period N repeated. In particular, in every interval n . n-1 the respective thermal energy of the traction battery E _{Bat, n} . E _{Bat, n-1} determined and the difference formed from these values, so as to take into account changes in the thermal energy budget of the traction battery.

Notwithstanding the present embodiment, the order of the steps 100 to 500 also be different, or it can also be steps 100 to 500 parallel, ie be carried out simultaneously or simultaneously. For example, the method can also be used with the step 400 begin, followed by the steps 100 to 300 , then with the step 500 to end, or it can, for example, the steps 300 and 400 be carried out at the same time.

Thus, without metrological detection of a coolant flow by means of flow sensors, it is possible to conclude by a comparison of the absorbed and the provided cooling capacity or values representative thereof for a disturbance in the coolant circuit.

LIST OF REFERENCE NUMBERS

2

contraption

4

Comparative value determination means

6

Reference value determination means

8th

comparator

10

output device

100

step

200

step

300

step

400

step

500

step

AS

control signal

B _K

provided cooling capacity

BT _n

Battery temperature in the 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

pre-interval

N

period

LA

input

P _K

absorbed cooling capacity

P _V

Heat energy loss

RW

reference value

UT _n

Ambient temperature in the interval n

VW

comparison value

.DELTA.T

temperature difference

ΔTλs

Battery heat flow

.lambda..sub.s

battery constant

Claims (14)

A method of monitoring a cooling device for cooling a traction battery, comprising the steps of: determining a comparison value (VW) representative of the cooling power (P _K ) received by the battery, determining a reference value (RW) representative of that of the cooling device provided cooling power (B _K ), comparing the comparison 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 issuing an error message the error signal (FS). Method according to Claim 1 , wherein for the determination of the comparison value (VW) a value representative of a battery temperature (BT _n ) and a value representative of an ambient temperature (UT _n ) are detected and evaluated. Method according to Claim 2 , wherein a temperature difference (ΔT) is determined by evaluating the representative value for the battery temperature (BT _n ) and the representative value for the ambient temperature (UT _n ), and the comparison value (VW) is determined by taking the temperature difference (ΔT). Method according to Claim 3 wherein, evaluating a battery constant (As) for the battery and the temperature difference (ΔT), a representative value for a battery thermal current (ΔTλs) of the traction battery is determined, and the comparison value (VW) is determined using the representative value for the battery thermal current (ΔTλS) becomes. Method according to one of Claims 1 to 4 wherein the comparison value (VW) is determined using a representative value for a thermal energy of the battery (E _{Bat, n} ). Method according to Claim 5 in which the comparison value (VW) is determined at intervals (n, n-1), and 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 of the battery (E _{Bat, n-1} ) in a pre-interval (n-1). Computer program product comprising program modules adapted to perform a method according to any one of Claims 1 to 6 perform. Device (2) for monitoring a cooling device for cooling a traction battery, having a comparison value determination device (4) for determining a comparison value (VW), which is representative of the cooling power (P _K ) received by the battery, of a reference value determination device (6) for determining a Reference value (RW) representative of the cooling power (B _K ) provided by the cooling device, comparison means (8) for comparing the comparison value (VW) with the reference value (RW), and output means (10) for generating and outputting one Error signal (FS), if there is a difference between the comparison value (VW) and the reference value (RW) and for issuing an error message to the error signal (FS). Device (2) according to Claim 8 wherein the comparison value determining means (4) is adapted to provide a for. to detect and evaluate a battery temperature (BT _n ) representative value and a value representative of an ambient temperature (UT _n ). Device (2) according to Claim 9 wherein comparison value determination device (4) is designed to determine a temperature difference (ΔT) by evaluating the representative value for the battery temperature (BT _n ) and the representative value for the ambient temperature (UT _n ), and using the comparison value (VW) Temperature difference (ΔT) to determine. Device (2) according to Claim 10 wherein the comparison value determination device (4) is designed to determine a representative value for a battery thermal current (ΔTλs) of the traction battery by evaluating a battery constant (λs) for the traction battery and the temperature difference (ΔT), and using the comparison value (VW) representative value for the battery heat flux (ΔTλs). Device (2) according to one of Claims 8 to 11 wherein the comparison value determining means (4) is adapted to determine the comparison value (VW) using a representative value for a thermal energy of the battery (E _Bat ). Device (2) according to Claim 12 wherein the comparison value determining means (4) is adapted to determine the comparison value (VW) at intervals (n, n-1 ₁ ), and the comparison value (VW) using a representative value for a thermal energy (E _{Bat, n} ) of the traction battery at 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). Motor vehicle with a device (2) according to one of Claims 8 to 13 ,

Images