System and method for battery pack management using predictive balancing

Patent metadata

Field	Value
Publication number	US-9979211-B2
Application number	US-201514844184-A
Country	US
Kind code	B2
Filing date	Sep 3, 2015
Priority date	Sep 15, 2012
Publication date	May 22, 2018
Grant date	May 22, 2018

Abstract

Predictive battery pack cell balancing apparatus and methods are presented in which active bypass current switching is controlled according to initial balancing bypass current values to balance the cell depth of discharge (DOD) values by the end of a charging/discharging time period, and according to continuous balancing bypass current values representing an amount of bypass current needed to maintain a present relationship of the cell DOD values.

First claim

What is claimed is:

1. A controller for use in a battery pack management system having a pack of battery cells and a bypass circuit coupled to the pack of battery cells, the controller comprising:
a balancing circuit configured to:
determine an initial balancing bypass current value of each of the battery cells to balance among depth of discharge (DOD) values of the battery cells by a prospective end time of a battery operation;
determine a continuous balancing bypass current value of each of the battery cells to maintain a relationship of the balanced DOD values; and
determine a requested cell bypass current value of each of the battery cells based on the initial balancing bypass current value and the continuous balancing bypass current value; and
generate an on-time signal having an on-time period based on a ratio of the requested cell bypass current value to an estimated maximum bypass current value; and

a switching control circuit configured to receive the on-time signal and generate a switching control signal based on the on-time signal, the switching control signal, upon being received by the bypass circuit, configured to cause the bypass circuit to transfer charges between two of the battery cells during the on-time period.

2. The controller of claim 1 , wherein the switching control signal has a switching frequency during the on-time period of the on-time signal, and the bypass circuit is configured to conduct a bypass current between the two of the battery cells at the switching frequency.

3. The controller of claim 1 , wherein the balancing circuit is configured to determine the initial balancing bypass current value based on an estimated present DOD value of the respective one of the battery cells.

4. The controller of claim 3 , wherein the estimated present DOD value is determined based on a battery model of the respective one of the battery cells and a measured cell voltage of the respective one of the battery cells.

5. The controller of claim 3 , further comprising:
a dynamic voltage correlation circuit configured to determine the estimated present DOD value based on a battery model of the respective one of the battery cells and a measured cell voltage of the respective one of the battery cells.

6. The controller of claim 1 , wherein the balancing circuit is configured to determine the continuous balancing bypass current value based on a difference in total charge capacity values of the pack of battery cells and a total pack current value of the pack of battery cells.

7. The controller of claim 1 , wherein the requested cell bypass current value of the respective one of the battery cells is a summation of the initial balancing bypass current value and the continuous balancing bypass current value of the respective one of the battery cells.

8. The controller of claim 1 , wherein the switching control circuit is configured to reduce a switching frequency of the switching control signal if the on-time period is greater than a predetermined time interval, and the balancing circuit is configured to update the on-time period based on the reduced switching frequency.

9. A controller for use in a battery pack management system having a pack of battery cells and a bypass circuit coupled to the pack of battery cells, the controller comprising:
a balancing circuit configured to:
determine an initial balancing bypass current value of each of the battery cells based on an estimated present depth of discharge (DOD) value of the respective one of the battery cells;
determine a continuous balancing bypass current value of each of the battery cells based on a difference in total charge capacity values of the pack of battery cells and a total pack current value of the pack of battery cells; and
determine a requested cell bypass current value of each of the battery cells based on a summation of the initial balancing bypass current value and the continuous balancing bypass current value of the respective one of the battery cells; and
generate an on-time signal having an on-time period based on a ratio of the requested cell bypass current value to an estimated maximum bypass current value; and

a switching control circuit configured to receive the on-time signal and generate a switching control signal based on the on-time signal, the switching control signal, upon being received by the bypass circuit, configured to cause the bypass circuit to transfer charges between two of the battery cells during the on-time period.

10. The controller of claim 9 , wherein the switching control signal has a switching frequency during the on-time period of the on-time signal, and the bypass circuit is configured to conduct a bypass current between the two of the battery cells at the switching frequency.

11. The controller of claim 9 , wherein the estimated present DOD value is determined based on a battery model of the respective one of the battery cells and a measured cell voltage of the respective one of the battery cells.

12. The controller of claim 9 , further comprising:
a dynamic voltage correlation circuit configured to determine the estimated present DOD value based on a battery model of the respective one of the battery cells and a measured cell voltage of the respective one of the battery cells.

13. The controller of claim 9 , wherein the switching control circuit is configured to reduce a switching frequency of the switching control signal if the on-time period is greater than a predetermined time interval, and the balancing circuit is configured to update the on-time period based on the reduced switching frequency.

14. A method for managing a pack of battery cells coupled to a bypass circuit, the method comprising:
determining, by a controller, an initial balancing bypass current value of each of the battery cells to balance among depth of discharge (DOD) values of the battery cells by a prospective end time of a battery operation;
determining, by the controller, a continuous balancing bypass current value of each of the battery cells to maintain a relationship of the balanced DOD values; and
determining, by the controller, a requested cell bypass current value of each of the battery cells based on the initial balancing bypass current value and the continuous balancing bypass current value; and
determining, by the controller, an on-time period based on a ratio of the requested cell bypass current value to an estimated maximum bypass current value; and
generating a switching control signal based on the on-time period, the switching control signal, upon being received by the bypass circuit, configured to cause the bypass circuit to transfer charges between two of the battery cells during the on-time period.

15. The method of claim 14 , wherein the switching control signal has a switching frequency during the on-time period, and the bypass circuit is configured to conduct a bypass current between the two of the battery cells at the switching frequency.

16. The method of claim 15 , further comprising:
reducing, by the controller, the switching frequency of the switching control signal if the on-time period is greater than a predetermined time interval; and
updating, by the controller, the on-time period based on the reduced switching frequency.

17. The method of claim 14 , wherein the determining the initial balancing bypass current value is based on an estimated present DOD value of the respective one of the battery cells.

18. The method of claim 17 , wherein the estimated present DOD value is determined based on a battery model of the respective one of

Assignees

• Texas Instruments Inc

Inventors

• Barsukov Yevgen Pavlovich
• Zhang Yandong
• Battle Jason Michael
• Galburt Konstantin

Classifications

• H02J7/82

  Control of state of charge [SOC] · CPC title

• H02J7/54 Primary

  Passive balancing, e.g. using resistors or parallel MOSFETs · CPC title

• H02J7/0016 Primary

  Electricity · mapped topic

• H02J7/0021

  Electricity · mapped topic