Method for prediction of electrical characteristics of an electrochemical storage battery

• US 20050052158A1
• Filed: 08/05/2004
• Published: 03/10/2005
• Est. Priority Date: 08/06/2003
• Status: Active Grant

• Current Assignee: VB Autobatterie GmbH
• Original Assignee: VB Autobatterie GmbH
• Inventors: Meissner, Eberhard
• Granted Patent: US 7,253,587 B2
• Time in Patent Office: Days
• US Class Current: 320/132
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/3828 using current integration
• CPC Class Codes: G01R 31/392 Determining battery ageing or deterioration, e.g. state of health

Abstract

A method for prediction of electrical characteristics of an electrochemical storage battery and includes determining a functional relationship between a state of charge value which is related to a first parameter for a storage battery and a second state of charge value which is related to a second parameter for the storage battery for a second phase of use of the storage battery. The method also includes determining at least one characteristic variable from the reference of the functional relationship for the second phase to a state characteristic variable profile for a previous first phase of use of the storage battery. The method further includes predicting electrical characteristics of the storage battery utilizing a functional relationship between the characteristic variable and the electrical characteristics.

Claims

1. A method for prediction of electrical characteristics of an electrochemical storage battery, the method comprising:

determining a functional relationship between a state of charge value which is related to a first parameter for a storage battery and a second state of charge value which is related to a second parameter for the storage battery for a second phase of use of the storage battery;

determining at least one characteristic variable from the reference of the functional relationship for the second phase to a state characteristic variable profile for a previous first phase of use of the storage battery; and

predicting electrical characteristics of the storage battery utilizing a functional relationship between the characteristic variable and the electrical characteristics.

2. The method of claim 1 further comprising determining a state characteristic variable profile for the first phase as a functional relationship between the state of charge value which is related to the first parameter for the storage battery and the state of charge value which is related to the second parameter for the storage battery, wherein the change in the state characteristic variable profile from the first phase to the second phase is a measure of the state of electrolyte in the storage battery.

3. The method of claim 2 further comprising determining at least one of an acid capacity, a water loss, and an acid stratification of the electrolyte as a function of the change in the state characteristic variable profile from the first phase to the second phase.

4. The method of claim 1 wherein the first parameter is a voltage of the storage battery.

5. The method of claim 4 wherein the second parameter is a charge throughput of the storage battery.

6. The method of claim 5 further comprising determining the second state of charge value by balancing the current which has flowed between a first operating time and a second operating time as the transferred amount of charge.

7. The method of claim 6 further comprising determining a respective characteristic variable for the first phase and for the second phase from the ratio of the change in the state of charge value which relates to the first parameter to the change in the state of charge value which relates to the second parameter, or of the rest voltage change which relates to the amount of charge transferred during the electrical load phase, as the difference between the rest voltage after the electrical load phase and the rest voltage before the electrical load phase, using the formula

8. The method of claim 7 further comprising determining the acid capacity of the storage battery for the first phase as a function of the characteristic variable state, with the acid capacity being inversely proportional to the characteristic variable state.

9. The method of claim 8 further comprising measuring a rest voltage in an unloaded state for the storage battery after a rest voltage phase.

10. The method of claim 9 further comprising calculating the rest voltage from a time profile of battery terminal voltage during an approximately unloaded phase.

11. The method of claim 9 further comprising calculating the rest voltage from a voltage and current profile during use of the storage battery.

12. The method of claim 1 further comprising calculating an instantaneous relative state of charge value which relates to an acid capacity of electrolyte for the first phase from an instantaneous unloaded voltage using the formula

13. The method of claim 12 further comprising calculating an instantaneous absolute state of charge, which relates to the acid capacity of the electrolyte, for the first phase using the formula

14. The method of claim 13 further comprising calculating an instantaneous relative state of charge value, which relates to the acid capacity of the electrolyte, for the second phase from the instantaneous unloaded voltage using the formula

15. The method of claim 14 further comprising calculating an instantaneous absolute state of charge value, which relates to the acid capacity for the second phase, using the formula

SOC_1,abs″

=SOC_1,rel.″

Q₀.

16. The method of claim 15 further comprising determining a measure for wear of the storage battery in the second phase from the characteristic variables S′

for the first phase and S″

for the second phase based on the ratio S″

/S′

or as the relative change (S″

−

S′

)/S′

.

17. The method of claim 15 further comprising determining the end of the first phase by integration of the amount of charge throughput for the storage battery, with the first phase being ended when the integrated charge throughput exceeds a fixed minimum value.

18. The method of claim 17 wherein the only contributions which are taken into account for the integration of the charge throughput are those for which the changes in the state of charge value exceed a fixed minimum value.

19. The method of claim 15 further comprising determining the end of the first phase as a function of one of a fixed minimum time after initial use of the storage battery and a fixed minimum operating period.

20. The method of claim 15 further comprising determining the end of the first phase when acid stratification has been identified.

21. The method of claim 15 further comprising determining the storage capability of the storage battery by means of a functional relationship between the characteristic variable and the storage capability.

22. The method of claim 21 wherein the storage capability is determined by the following steps:

extrapolating of the state characteristic variable profile for the first phase and the functional relationship for the second phase at defined points or in defined sections to a zero value of the state of charge value which relates to the first parameter;

determining the state of charge values which relate to the second parameter for the first phase and for the second phase with the aid of the state characteristic variable profile for the first phase, and of the functional relationship for the second phase for a state of charge value which relates to the first parameter and is equal to zero;

determining a characteristic variable which relates to the second parameter from the difference between the state of charge value which relates to the second parameter for the first phase and the state of charge value which relates to the second parameter for the second phase;

determining a state of charge value which relates to the first parameter for the first phase and a state of charge value which relates to the first parameter for the second phase from the state characteristic variable profile and from the functional relationship with a state of charge value which relates to the second parameter and is equal to zero;

determining a characteristic variable which relates to the first parameter from the difference between the state of charge value which relates to the first parameter for the first phase, and the state of charge value which relates to the first parameter for the second phase;

determining the storage capability of the storage battery from the functional relationship between the characteristic variable which relates to the first parameter, the characteristic variable which relates to the second parameter, and the storage capability.

23. The method of claim 22 wherein the storage capability is calculated using the formula CSC=100−

MAX(G₁, G₂), where CSC is the storage capability of the storage battery, G₁ is the characteristic variable which relates to the first parameter, and G₂ is the characteristic variable which relates to the second parameter.

24. The method of claim 22 wherein the extrapolating step is carried out in areas of charge values greater than 50%.

25. The method of claim 1 further comprising determining an amount of charge which can be drawn in an instantaneous state from the difference between a state of charge value and the characteristic variable as the value of the state of charge value which is related to the second parameter from the functional relationship with the state of charge value which is related to the first parameter and is equal to zero, and with the difference multiplied by the battery capacity representing the amount of charge which can still be drawn in the instantaneous state.

26. The method of claim 1 further comprising using a state of charge value to determine a voltage change to be expected when an electrical load is applied to the storage battery at a temperature, as a function of the relationship, which is dependent on the characteristic variable for the state of charge, between the voltage change and the electrical load.

27. The method of claim 1 further comprising:

determining a rest voltage of the storage battery at a first time in the second phase as a measure of the state of charge value;

determining a rest voltage to be expected between the first time and a second time after a charge throughput, from the functional relationship for the second phase;

determining a state of charge value for the second time;

determining the voltage change to be expected from the determined rest voltage to be expected, the state of charge value and a function of the electrical internal resistance as a function of the state of charge value which is related to the first parameter; and

determining a voltage to be expected as the difference between the rest voltage expected for the second time and the product of the internal resistance and an assumed current value.

28. The method of claim 1 further comprising:

determining a rest voltage of the storage battery at a first time in the second phase as the state of charge value;

determining a rest voltage to be expected between the first time and a second time after a charge throughput, from the functional relationship for the second phase;

determining the voltage change to be expected from the determined rest voltage to be expected, the state of charge value and a function of the voltage difference, as a function of the state of charge value which is related to the first parameter; and

determining a voltage to be expected as the difference between the rest voltage expected at the second time and the determined voltage change.