BATTERY LIFE ESTIMATION

• US 20100250162A1
• Filed: 03/24/2009
• Published: 09/30/2010
• Est. Priority Date: 03/24/2009
• Status: Active Grant

• Current Assignee: Schneider Electric IT Corporation (Schneider Electric SE)
• Original Assignee: American Power Conversion Corporation (Schneider Electric SE)
• Inventors: White, Kevin, Cohen, Daniel C.
• Granted Patent: US 8,407,018 B2
• Time in Patent Office: Days
• US Class Current: 702/63
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/392 Determining battery ageing or deterioration, e.g. state of health
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A method of estimating battery lifetime includes monitoring a charge characteristic of a battery during a first time period, monitoring an operating condition of the battery, determining a first battery life value for the first time period based on the operating condition of the battery, the charge characteristic, and a duration of the first time period, determining an overall battery life value using the first battery life value and a second battery life value for a second time period, and estimating a remaining battery lifetime for the battery based on the overall battery life value.

Claims

1. A method of estimating battery lifetime, the method comprising:

monitoring a charge characteristic of a battery during a first time period;

monitoring an operating condition of the battery;

determining a first battery life value for the first time period based on the operating condition of the battery, the charge characteristic, and a duration of the first time period;

determining an overall battery life value using the first battery life value and a second battery life value for a second time period; and

estimating a remaining battery lifetime for the battery based on the overall battery life value.

2. The method of claim 1 wherein the first time period is a float time period, the operating condition comprises operating temperature of the battery, the charge characteristic comprises a float voltage applied to the battery, and determining the first battery life value is based on the duration of the first time period, the operating temperature of the battery during the first time period, and the float voltage.

3. The method of claim 2 wherein determining the first battery life value further comprises determining a float life contribution and scaling the float life contribution to account for a rate of chemical reaction of the battery at the operating temperature.

4. The method of claim 2 further comprising adjusting a level of the applied float voltage to compensate for the operating temperature of the battery, and wherein determining the first battery life value comprises determining a float life contribution and scaling the float life contribution to account for an adjusted float voltage level applied during the first time period.

5. The method of claim 1 wherein the first time period is a float time period, the operating condition of the battery comprises a discharge of the battery during a discharge in a third time period prior to the first time period, and the charge characteristic comprises a float voltage applied to the battery, the method further comprising:

monitoring discharge of the battery during the third time period; and

determining a discharge rate at which the battery was discharged during the third time period,

wherein determining the first battery life value comprises;

determining a float life contribution based on the float voltage and the duration of the first time period; and

scaling the float life contribution to account for the battery being discharged at the discharge rate during the third time period.

6. The method of claim 5 further comprising reducing an effect that the scaling has on the float life contribution based on an amount of time that the third time period preceded the first time period.

7. The method of claim 5 wherein the discharge event in the third time period is a most recent one of a plurality of discharge events that occurred prior to the first time period.

8. The method of claim 5 wherein the float life value comprises a decrement to the overall battery life and sealing the float life decrement comprises applying a scale factor to the float life decrement, wherein a first scale factor for a first discharge rate results in a smaller scaled float life decrement for the first time period than does a second scale factor for a second discharge rate with the first discharge rate being lower than the second discharge rate.

9. The method of claim 1 wherein the first time period is a discharge period, the method further comprising:

monitoring discharge of the battery during the discharge period;

determining, for the discharge period, a rate and/or depth of discharge of the battery; and

determining an estimated number of discharge cycles based on the discharge rate and/or the depth of discharge,

wherein determining the first battery life value comprises determining a cycle life contribution for the first time period based on the estimated number of discharge cycles.

10. The method of claim 1 further comprising:

determining a capacity of the battery by performing a state of health test; and

adjusting the remaining battery lifetime based on the determined capacity.

11. An apparatus for estimating battery lifetime, the apparatus comprising:

a battery monitor configured to monitor a charge characteristic of a battery during a first time period;

a life value module coupled to the battery monitor and configured to monitor an operating condition of the battery, determine a first battery life value for the first time period based on the operating condition of the battery, the charge characteristic, and a duration of the first time period, and determine an overall battery life value using the first battery life value and a second battery life value for a second time period; and

a remaining life module coupled to the life value module and configured to estimate a remaining battery lifetime for the battery based on the overall battery life value.

12. The apparatus of claim 11 wherein the first time period is a float time period and the life value module is a float life value module, the battery monitor is configured to monitor a float voltage applied to the battery during the first period, and the float life value module is configured to monitor the operating temperature of the battery and determine the first battery life value based on the duration of the first time period, the operating temperature of the battery during the first time period, and the float voltage.

13. The apparatus of claim 12 wherein the float life value module is configured to determine the first battery life value by determining a float life contribution and scaling the float life contribution to account for a rate of chemical reaction of the battery at the operating temperature.

14. The apparatus of claim 12 wherein a level of the applied float voltage is adjusted to compensate for the operating temperature of the battery, and the float life value module is configured to determine the first battery life value by determining a float life contribution and scaling the float life contribution to account for an adjusted float voltage level applied during the first time period.

15. The apparatus of claim 11 wherein the first time period is a float time period and the life value module is a float life value module, the battery module is configured to monitor a float voltage applied to the battery during the first time period, and the float life value module is configured to monitor discharge of the battery during a third time period prior to the first time period, determine a discharge rate at which the battery was discharged during the third time period, and determine the first battery life value by determining a float life contribution based on the float voltage and the duration of the first time period, and scaling the float life contribution to account for the battery being discharged at the discharge rate during the third time period.

16. The apparatus of claim 15 wherein the float life module is further configured to reduce an effect that the scaling has on the float life contribution based on an amount of time that the third time period preceded the first time period.

17. The apparatus of claim 15 wherein the discharge event in the third time period is a most recent one of a plurality of discharge events that occurred prior to the first time period.

18. The apparatus of claim 15 wherein the float life value comprises a decrement to the overall battery life and the float life module scales the float life decrement by applying a scale factor to the float life decrement, wherein a first scale factor for a first discharge rate results in a smaller sealed float life decrement for the first time period than does a second scale factor for a second discharge rate with the first discharge rate being lower than the second discharge rate.

19. The apparatus of claim 11 wherein the first time period is a discharge period, and the life value module is a cycle life value module, the battery monitor monitors discharge of the battery during the discharge period, and the cycle life value module is configured to determine, for the discharge period, a rate and/or depth of discharge of the battery, determine an estimated number of discharge cycles based on the discharge rate and/or the depth of discharge, and determine the first battery life value by determining a cycle life contribution for the first time period based on the estimated number of discharge cycles.

20. The apparatus of claim 11 further comprising:

a state of health module configured to determine a capacity of the battery by performing a state of health test;

wherein

the remaining life module is further configured to adjust the remaining battery lifetime based on the determined capacity.

21. An apparatus for estimating battery lifetime, the apparatus comprising:

a battery monitor configured to monitor a float voltage applied to a battery during a first time period and monitor a charge characteristic of the battery;

a float life value module coupled to the battery monitor and configured to monitor an operating condition of the battery, and determine a first float life contribution based on the operating condition of the battery, the float voltage, and a duration of the first time period, and determine an overall float life value using the first float life contribution and a second float life contribution for a second time period;

a cycle life value module coupled to the battery monitor and configure to determine, for a third time period, a rate and/or depth of discharge of the battery, determine an estimated number of discharge cycles based on the discharge rate and/or the depth of discharge, determine a first cycle life contribution for the first time period based on the estimated number of discharge cycles, and determine an overall cycle life value using the first cycle life contribution and a second cycle life contribution for a fourth time period; and

a remaining life module coupled to the float life value module and the cycle life value module and configured to estimate a remaining battery lifetime for the battery based on the overall float life value and the overall cycle life value.