Method and system for monitoring and balancing cells in battery packs utilizing optically coupled cell voltage selection signal, cell voltage isolation amplifier, and zener diodes in balancing circuit

• US 7,723,955 B2
• Filed: 07/19/2007
• Issued: 05/25/2010
• Est. Priority Date: 07/19/2006
• Status: Active Grant

• Current Assignee: A123 Systems Incorporated
• Original Assignee: A123 Systems Incorporated
• Inventors: Toth, Akos, Zaag, Nader
• Primary Examiner(s): Tso; Edward
• Assistant Examiner(s): HERNANDEZ, MANUEL J
• Application Number:
  US11/780,296
• Publication Number:
  US 20080018300A1
• Time in Patent Office: 1,041 Days
• Field of Search: 320/118, 320/119, 320/132
• US Class Current: 320/118
• CPC Class Codes: B60L 2210/10 DC to DC converters
• CPC Class Codes: B60L 2240/545 Temperature
• CPC Class Codes: B60L 2240/547 Voltage
• CPC Class Codes: B60L 2240/549 Current
• CPC Class Codes: B60L 3/0046 relating to electric energy storage systems, e.g. batteries or capacitors
• CPC Class Codes: B60L 3/04 Cutting off the power supply under fault conditions protective devices and circuit arrangements in general H01H; H02H
• CPC Class Codes: B60L 58/14 Preventing excessive discharging
• CPC Class Codes: B60L 58/15 Preventing overcharging
• CPC Class Codes: B60L 58/18 of two or more battery modules
• CPC Class Codes: B60L 58/22 Balancing the charge of battery modules
• CPC Class Codes: B60L 58/25 by controlling the electric load
• CPC Class Codes: H02J 7/0019 using switched or multiplexed charge circuits
• 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 10/72 Electric energy management in electromobility

Abstract

A system for balancing energy delivery devices within the one or more battery packs and for providing isolated monitoring of the battery packs includes at least one group of energy delivery devices electrically connected in series. For each group of energy delivery devices, the system includes a balancing circuit for each adjacent pair of energy delivery devices. The balancing circuit adjusts charge stored in each energy delivery device of the pair so that the charge stored in the energy delivery devices of the pair is substantially equal, and the charge stored in each energy delivery device remains above a threshold. The system also includes a voltage monitoring module for sequentially selecting each of the energy delivery devices and providing a voltage associated with the selected device at an output port. The voltage monitoring module uses a low on-resistance differential multiplexer to select each of the energy delivery devices.

Claims

1. A system for balancing energy delivery devices within the one or more battery packs, comprising:

at least one group of N energy delivery devices electrically connected in series, wherein N is an integer greater than one;

for each group of N energy delivery devices, a balancing circuit for each adjacent pair of energy delivery devices, wherein the balancing circuit adjusts charge stored in each energy delivery device of the adjacent pair so that (i) the charge stored in a first energy delivery device of the pair is substantially equal to a second energy delivery device of the pair, and (ii) the charge stored in each energy delivery device remains above a predetermined threshold; and

a pair of Zener diodes arranged in a back-to-back configuration included in the balancing circuit, wherein current flow is blocked from one of the energy delivery devices in the adjacent pair if the other energy delivery device in the adjacent pair becomes disconnected.

2. The system of claim 1, wherein the Zener diodes maintain the charge stored in each energy delivery device above the predetermined threshold.

3. The system of claim 1, wherein the balancing circuit maintains the charge stored in each energy delivery device.

4. The system of claim 1, further including a voltage monitoring module for sequentially selecting each of the energy delivery devices and providing a voltage associated with the selected energy delivery device at an output port, wherein the voltage monitoring module uses a low on-resistance differential multiplexer to select each of the energy delivery devices and provide the associated voltage.

5. The system of claim 4, wherein the differential multiplexer is powered by a split supply circuit.

6. The system of claim 4, wherein the voltage monitoring module provides isolation between the energy delivery devices and the output port.

7. The system of claim 6, wherein the isolation includes passing select signals for the multiplexer through optical isolators, and passing the voltage associated with the selected energy delivery device through an isolation amplifier.

8. The system of claim 1, further including a temperature monitoring module for receiving a signal representative of a temperature associated with the battery pack and one or more other battery packs, and for selectively providing one of the received signals at an output port.

9. The system of claim 4, wherein the balancing circuits and the voltage monitoring module are combined in a single printed circuit board.

10. The system of claim 1, wherein each energy delivery device is a lithium cell.

11. A system for providing isolated monitoring of one or more battery packs, and for balancing energy delivery devices within the one or more battery packs, comprising:

at least one group of N energy delivery devices electrically connected in series, wherein N is an integer greater than one;

for each group of N energy delivery devices, a balancing module and a voltage monitoring module;

wherein the balancing module includes a balancing circuit for each adjacent pair of energy delivery devices;

wherein the balancing circuit adjusts charge stored in each energy delivery device of the adjacent pair so that (i) the charge stored in a first energy delivery device of the pair is substantially equal to a second energy delivery device of the pair, and (ii) the charge stored in each energy delivery device remains above a predetermined threshold; and

,

wherein the voltage monitoring module includes;

(i) a differential multiplexer, operating on split supply, for sequentially selecting each of the energy delivery devices presented to a plurality of input ports and providing a voltage associated with the selected energy delivery device at an output port, wherein the differential multiplexer is characterized by a low on-resistance path from the input ports to the output port;

(ii) a resistor divider for scaling the voltage associated with the selected energy delivery device to produce a scaled voltage;

(iii) an isolation amplifier for providing an isolated version of the scaled voltage;

(iv) an isolated DC to DC converter for supplying power to an input side of the isolation amplifier, and

(v) an output operational amplifier for impedance matching the scaled voltage to a system controller.

12. The system of claim 11, wherein the balancing circuit includes a pair of Zener diodes, arranged in a back-to-back configuration, for maintaining the charge stored in each energy delivery device.

13. The system of claim 12, further including (i) an operational amplifier for determining a level of charge imbalance between the adjacent pair of energy delivery devices and producing an error signal corresponding the level of charge imbalance, and (ii) a stacked transistor pair arranged to redistribute the charge of the adjacent pair of energy delivery devices according to the error signal.

14. The system of claim 11, wherein the differential multiplexer is powered by a split supply circuit.

15. The system of claim 11, further including a temperature monitoring module for receiving a signal representative of a temperature associated with the battery pack and one or more other battery modules, and for selectively providing one of the received signals at an output port.

16. The system of claim 11, wherein each energy delivery device is a lithium cell.

17. A method of balancing energy delivery devices within a battery pack, wherein the battery pack includes a group of N energy delivery devices electrically connected in series, N being an integer greater than one, comprising:

for each adjacent pair of energy delivery devices within the battery pack, adjusting charge stored in each energy delivery device of the adjacent pair so that the charge stored in the energy delivery devices of the pair is substantially equal, maintaining the charge stored in each energy delivery device above a predetermined threshold, and blocking current flow from one of the energy delivery devices in the adjacent pair if the other energy delivery device in the adjacent pair becomes disconnected.

18. The method of claim 17, further including redistributing charge between the adjacent pair of energy delivery devices with a redistribution circuit, wherein the redistribution circuit includes a pair of Zener diodes, arranged in a back-to-back configuration for maintaining the charge stored in each energy delivery device above a predetermined threshold.

19. The method of claim 17, further including sequentially selecting each of the energy delivery devices with a low on-resistance differential multiplexer, and providing a voltage associated with the selected energy delivery device.

20. The method of claim 17, further including supplying power to the differential multiplexer from a split supply circuit.