MODULE BYPASS SWITCH WITH BYPASS CURRENT MONITORING

• US 20120319658A1
• Filed: 06/12/2012
• Published: 12/20/2012
• Est. Priority Date: 06/17/2011
• Status: Active Grant

• Current Assignee: Southwest Electronic Energy Corporation (Ultralife Corporation)
• Original Assignee: Southwest Electronic Energy Corporation (Ultralife Corporation)
• Inventors: White, David A., Benckenstein, Claude L. Jr.
• Granted Patent: US 9,190,855 B2
• Time in Patent Office: Days
• US Class Current: 320/134
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: H02J 7/0019 using switched or multiplexed charge circuits
• CPC Class Codes: H02J 7/0047 with monitoring or indicating devices or circuits

Abstract

A battery pack system module may include a module bypass switch for allowing charge current to bypass the battery pack system module. The module bypass switch may be activated to divert charging current from the battery pack system module to other battery pack system modules. The charging current may be diverted to bring other battery pack system modules into balance with the battery pack system module. That is, to bring the state of charge of all battery pack system modules into coarse balance. When the module bypass switch is activated, charging current through the module bypass switch may be monitored by a current sensing device such as a current sensing resistor. A microprocessor may receive information about the bypass current level and use the information to determine when to de-activate the module bypass switch. Sensing current through a module bypass switch allows more accurate and quicker inter-module balancing.

Claims

1. An apparatus, comprising:

a first battery pack system module, comprising;

a battery cell coupled between a first terminal and a second terminal;

a charge switch coupled in series with the battery cell and the first terminal for interrupting charging of the battery cell;

a discharge switch coupled in series with the charge switch and the first terminal for interrupting discharging of the battery cell;

a module bypass switch for shorting the first terminal and the second terminal; and

a current measurement device coupled between the module bypass switch and at least one of the first terminal and the second terminal

2. The apparatus of claim 1, further comprising a zener diode in series with a resistor, the zener diode and the resistor in parallel with the module bypass switch.

3. The apparatus of claim 1, in which the module bypass switch is a field effect transistor (FET).

4. The apparatus of claim 1, further comprising a second battery pack system module coupled in series with the first battery pack system module.

5. The apparatus of claim 1, further comprising:

a controller assembly coupled to the charge switch, the discharge switch, the module bypass switch, and the current measurement device;

a bus coupled to the controller assembly; and

an initializer coupled to the bus.

6. The apparatus of claim 5, further comprising a pack sensing circuit coupled to the controller assembly.

7. The apparatus of claim 5, further comprising a fuse coupled between the discharge switch and the battery cell.

8. The apparatus of claim 5, further comprising an isolated bus interface coupled between the bus and the controller assembly.

9. The apparatus of claim 5, in which the controller assembly is configured to monitor a bypass current through the module bypass switch by measuring the bypass current from the current measuring device.

10. A method, comprising:

bypassing a charging current through a module bypass switch of a first battery pack system module without charging battery cells of the first battery pack system module;

monitoring the charging current through the module bypass switch of the first battery pack system module;

detecting, during the bypassing, that the charging current has fallen below a threshold value; and

stopping the bypassing of the charging current through the module bypass switch of the first battery pack system module when the charging current has fallen below the threshold value.

11. The method of claim 10, further comprising:

starting charging of the first battery pack system module after stopping the bypassing of the charging current; and

starting discharging of the first battery pack system module after stopping the bypassing of the charging current.

12. The method of claim 10, further comprising the following steps before bypassing the charging current:

charging a first battery pack system module with a charging current;

detecting, during the charging, that a voltage across the first battery pack system module has exceeded a threshold voltage;

stopping charging of the first battery pack system module after detecting the voltage has exceeded the threshold voltage;

stopping discharging of the first battery pack system module after detecting the voltage has exceeded the threshold voltage; and

activating a module bypass switch to pass the charging current through the first battery pack system module without charging the first battery pack system module after stopping discharging of the first battery pack system module.

13. The method of claim 12, in which stopping charging of the first battery pack system module comprises de-activating a charge switch.

14. The method of claim 12, in which stopping discharging of the first battery pack system module comprises de-activating a discharge switch.

15. The method of claim 10, further comprising charging a second battery pack system module with the charging current, in which the second battery pack system module is in series with the first battery pack system module.

16. The method of claim 10, in which the step of detecting, during the bypassing, that the charging current has fallen below a threshold value comprises monitoring a current sensing resistor.

17. A computer program product, comprising:

a non-transitory computer-readable medium comprising;

code to bypass a charging current through a module bypass switch of a first battery pack system module without charging battery cells of the first battery pack system module;

code to monitor the charging current through the module bypass switch of the first battery pack system module;

code to detect, during the bypassing, that the charging current has fallen below a threshold value; and

code to stop the bypassing of the charging current through the module bypass switch of the first battery pack system module when the charging current has fallen below the threshold value.

18. The computer program product of claim 17, in which the medium further comprises:

code to charge a first battery pack system module with a charging current;

code to detect, during the charging, that a voltage across the first battery pack system module has exceeded a threshold voltage;

code to stop charging of the first battery pack system module after detecting the voltage has exceeded the threshold voltage;

code to stop discharging of the first battery pack system module after detecting the voltage has exceeded the threshold voltage; and

code to activate a module bypass switch to pass the charging current through the first battery pack system module without charging the first battery pack system module after stopping discharging of the first battery pack system module.

19. The computer program product of claim 17, in which the medium further comprises:

code to monitor at least a second battery pack system module; and

code to enable charging of the second battery pack system module when charging of the first battery pack system module is disabled.

20. The computer program product of claim 17, in which the medium further comprises code to remotely monitor the charging of the first battery pack system module.