Control strategy for HV battery equalization charge during driving operation in fuel cell hybrid vehicles

• US 8,148,952 B2
• Filed: 07/14/2009
• Issued: 04/03/2012
• Est. Priority Date: 07/14/2009
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Schaffnit, Jochen
• Primary Examiner(s): RAMADAN, RAMY O
• Application Number:
  US12/502,969
• Publication Number:
  US 20110012558A1
• Time in Patent Office: 994 Days
• Field of Search: 320/116, 320/162
• US Class Current: 320/162
• CPC Class Codes: B60L 58/10 for monitoring or controlling batteries
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H01M 10/48 Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals, H01M50/569
• CPC Class Codes: H01M 10/482 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H02J 7/0014 Circuits for equalisation of charge between batteries
• CPC Class Codes: H02M 1/008 Plural converter units for generating at two or more independent and non-parallel outputs, e.g. systems with plural point of load switching regulators
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 90/12 Electric charging stations

Abstract

A system and method for equalizing the state of charge of the cells of a battery in an electric vehicle while the vehicle is being driven. The method includes monitoring the state of charge of the battery cells in the battery and measuring the actual current of the battery. The method also includes determining a maximum charge current limit of the battery and comparing the actual battery current and the charge current limit. The method also includes modifying the charge current limit based on the comparison between the actual battery current and the charge current limit. The method then converts the modified charge current limit to a power charge limit and then over charges the battery using a small amount of current and the power charge limit so that all of the cells in the battery become fully charged.

Claims

1. A method for equalizing the charge of battery cells in a battery in an electric vehicle, said method comprising:

monitoring the state of charge of the battery cells in the battery;

measuring the actual current of the battery;

determining a maximum charge current limit of the battery;

comparing the actual battery current and the maximum charge current limit;

modifying the maximum charge current limit based on the comparison between the actual battery current and the maximum charge current limit;

converting the modified maximum charge current limit to a power charge limit; and

overcharging the battery using the power charge limit so that all of the cells in the battery become fully charged.

2. The method according to claim 1 wherein overcharging the battery includes overcharging the battery with a current of about 2 amps.

3. The method according to claim 1 wherein a fuel cell stack in the electric vehicle provides the power to charge the battery cells.

4. The method according to claim 1 wherein converting the modified charge current limit to a power charge limit includes using a battery model.

5. The method according to claim 1 wherein comparing the actual battery current and the charge current limit includes comparing the actual battery current and the charge current limit in a proportional-integral controller.

6. The method according to claim 1 wherein measuring the actual current of the battery includes using a battery management system to measure the battery current.

7. The method according to claim 1 wherein modifying the maximum charge current limit includes adding a value to the maximum charge current limit.

8. The method according to claim 1 further comprising turning off a power-spilt calculation module that splits the power distribution between the battery and a fuel cell stack.

9. The method according to claim 1 further comprising initiating the method for equalizing the charge of battery cells in a battery if the state of charge of a minimum cell charge and a maximum cell charge in the battery exceeds a predetermined threshold.

10. A method for equalizing the charge of battery cells in a battery in a fuel cell hybrid vehicle including a fuel cell stack, said method comprising:

monitoring the state of charge of the battery cells in the battery;

measuring the actual current of the battery;

determining a maximum charge current limit of the battery;

comparing the actual battery current and the maximum charge current limit in a proportional-integral controller;

modifying the maximum charge current limit based on the comparison between the actual battery current and the maximum charge current limit by adding a value to the maximum charge current limit;

converting the modified maximum charge current limit to a power charge limit using a battery model; and

overcharging the battery using the power charge limit and power from the fuel cell stack so that all of the cells in the battery become fully charged.

11. The method according to claim 10 wherein overcharging the battery includes overcharging the battery with a current of about 2 amps.

12. The method according to claim 10 wherein measuring the actual current of the battery includes using a battery management system to measure the battery current.

13. The method according to claim 10 further comprising turning off a power-spilt calculation module that splits the power distribution between the battery and the fuel cell stack.

14. The method according to claim 10 further comprising initiating the method for equalizing the charge of battery cells in a battery if the state of charge of a minimum cell charge and a maximum cell charge in the battery exceeds a predetermined threshold.

15. A system for equalizing the charge of battery cells in a battery in an electric vehicle, said system comprising:

means for monitoring the state of charge of the battery cells in the battery;

means for measuring the actual current of the battery;

means for determining a maximum charge current limit of the battery;

means for comparing the actual battery current and the maximum charge current limit;

means for modifying the maximum charge current limit based on the comparison between the actual battery current and the maximum charge current limit;

means for converting the maximum modified charge current limit to a power charge limit; and

means for overcharging the battery using the power charge limit so that all of the cells in the battery become fully charged.

16. The system according to claim 15 wherein the means for converting the maximum modified charge current limit uses a battery model.

17. The system according to claim 15 wherein the means for comparing the actual battery current and the charge current limit uses a proportional- integral controller.

18. The system according to claim 15 wherein the means for measuring the actual current of the battery is a battery management system.

19. The system according to claim 15 wherein the means for overcharging the battery overcharges the battery with a current of about 2 amps.

20. The system according to claim 15 further comprising a means for turning off a power-split calculation module that splits the power distribution between the battery and a fuel cell stack during the charge equalization.