Device and method for ascertaining the temperature in an electrical battery

• US 20060202666A1
• Filed: 02/02/2006
• Published: 09/14/2006
• Est. Priority Date: 02/03/2005
• Status: Active Grant

• Current Assignee: Clarios Germany GmbH & Co. KG (Michael Tojner, PhD, LLD)
• Original Assignee: VB Autobatterie GmbH & Co. KGaA (Robert Bosch GmbH)
• Inventors: Laig-Hoerstebrock, Helmut, Shirazi, Sepher
• Granted Patent: US 7,609,032 B2
• Time in Patent Office: Days
• US Class Current: 320/150
• CPC Class Codes: G01K 7/42 Circuits effecting compensation of thermal inertia; Circuits for predicting the stationary value of a temperature
• CPC Class Codes: H01M 10/486 for measuring temperature
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A method for ascertaining the temperature in an electrical battery includes determining at least one temperature value at a temperature measuring point outside the battery in the vicinity of the battery; determining at least one electrical power value in dependence on a characteristic power variable associated with the operation of the battery; weighting the power values and the temperature values with an assigned weighting factor; and ascertaining the temperature in the electrical battery from an energy balance in dependence on the at least one weighted temperature value and the weighted electrical power values.

Claims

1. A method for ascertaining the temperature in an electrical battery comprising:

determining at least one temperature value at a temperature measuring point outside the battery in the vicinity of the battery;

determining at least one electrical power value in dependence on a characteristic power variable associated with the operation of the battery;

weighting the power values and the temperature values with an assigned weighting factor; and

ascertaining the temperature in the electrical battery from an energy balance in dependence on the at least one weighted temperature value and the weighted electrical power values.

2. The method of claim 1, further comprising integrating over time at least one electrical power value and at least one temperature value.

3. The method of claim 1, further comprising normalizing the at least one power value and continuously summing the at least one normalized power value and at least one temperature value in discrete time steps from the immediately previously ascertained battery temperature to ascertain the current battery temperature.

4. The method of claim 1, wherein the weighting factor is chosen in dependence on the current operating state of the battery.

5. The method of claim 1, wherein a characteristic power variable is the battery terminal current that can be measured at the battery terminals.

6. The method of claim 1, wherein the power values and temperature values are related to the thermal capacity of the battery.

7. The method of claim 1, wherein the temperature values are related to the thermal capacity of the assigned object at which the temperature is determined.

8. The method of claim 1, wherein the power values and temperature values are related to the sum of the thermal capacity of the battery and at least one further thermal capacity of an object contributing to the temperature equalization.

9. The method of claim 1, wherein the temperature value of an object contributing to the temperature equalization is determined with a system of equations of the kind:

T_O=T<sub>O−

1</sub>+(k_O1·

T_B+k_O2·

T_Mess−

k_O0·

T<sub>O−

1</sub>)/C_Odt
and
k_O1+k_O2=k_O0

where C_O is the thermal capacity of the object, T_B is the battery temperature, T_Mess is the temperature measured at the temperature measuring point, T<sub>O−

1</sub> is the temperature value of the object determined previously in time and k_O1, k_O2 and k_O0 are fixed constants.

10. The method of claim 1, further comprising ascertaining the battery temperature with a system of equations of the kind

$T_B=T_{B-1}+N/C_B·$

dt + { ∑

i = 1 n ⁢

k 1 ·

T 1 - k 0 ·

T B - 1 } / C B ·

dt

where T<sub>B−

1</sub> is the previously calculated battery temperature T_B, C_B is the thermal capacity of the battery, k_i with i=1 to n are the weighting factors and T_i is at least one (if n=1) temperature value measured at objects i in the vicinity of the battery, and where N is the power value.

11. The method of claim 10, wherein the sum of the weighting factors

$\sum _{}^{}$

i = 1 n ⁢

k 1

is equal to the weighting factor k_o for the previously ascertained battery temperature.

12. The method of claim 1, wherein the power value is calculated with a system of equations

$N=N_B+\sum _{}^{}$

j = 1 m ⁢

k j ⁢

 

·

N j

where N_B is a value proportional to the electrical power converted by the battery, N_J are values proportional to powers converted by components in the vicinity of the battery, and k_j are weighting factors.

13. The method of claim 12, wherein the power value proportional to the power converted by the battery is the product of the battery terminal current and the difference between the battery terminal voltage and the battery open-circuit voltage.

14. The method of claim 13, wherein the battery open-circuit voltage value is corrected by a constant voltage value characteristic of the battery system.

15. The method of claim 14, wherein the constant voltage value for a lead-acid storage battery is in the range from −

0.04 to −

0.08 V/cell.

16. The method of claim 1, wherein a further electrical power value describes the power converted by a shunt introduced into the battery circuit, and the shunt power value is calculated as the product of the shunt resistance and the square of the battery terminal current.

17. The method of claim 1, wherein a further electrical power value is the electrical power converted in a measuring circuit, and this electrical power is determined in dependence on the current and voltage measured at the measuring circuit.

18. The method of claim 1, wherein the weighting factor is dependent on the heat transfer values of the battery and the heat transfer values of the vicinity of the assigned object.

19. The method of claim 1, wherein the weighting factors are chosen based on the specific vicinity, on the type of a motor vehicle, and on the type of battery.

20. A device for ascertaining the temperature in an electrical battery comprising:

at least one temperature sensor arranged outside a battery in the vicinity of the battery;

a voltmeter for measuring battery terminal voltage; and

a device for ascertaining battery terminal current and having an evaluation unit, which is connected to the at least one temperature sensor, the voltmeter, and the device for ascertaining the battery terminal current, and is designed for carrying out the method comprising the steps of;

determining at least one temperature value at a temperature measuring point outside the battery in the vicinity of the battery;

determining at least one electrical power value in dependence on a characteristic power variable associated with the operation of the battery;

weighting the power values and the temperature values with an is assigned weighting factor; and

determining the temperature in the electrical battery from an energy balance in dependence on the at least one weighted temperature value and the weighted electrical power values.