Method of controlling discharge of a plurality of rechargeable batteries, and battery assembly

• US 6,373,226 B1
• Filed: 07/26/2000
• Issued: 04/16/2002
• Est. Priority Date: 07/30/1999
• Status: Expired due to Fees

• Current Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Inventors: Itou, Tsukasa, Narukawa, Satoshi
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): TIBBITS, PIA FLORENCE
• Application Number:
  US09/626,123
• Time in Patent Office: 629 Days
• Field of Search: 307/18, 307/23, 307/25, 307/29, 307/38, 307/39, 307/43, 307/48, 320/132, 320/134, 320/136
• US Class Current: 320/132
• CPC Class Codes: H01M 10/441 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H02J 7/0018 using separate charge circuits
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

The discharge method discharges a plurality of serially connected rechargeable batteries, wherein the remaining charge in each discharging rechargeable battery is detected, and a battery with the lowest remaining charge is designated a low charge rechargeable battery. The plurality of serially connected rechargeable batteries are discharged while supplying battery voltage stepped down from the output voltage of the serially connected rechargeable batteries to the low capacity rechargeable battery.

Claims

1. A method of discharging a plurality of serially connected rechargeable batteries comprising:

discharging the plurality of serially connected rechargeable batteries into a load;

measuring remaining charge in each rechargeable battery being discharged;

detecting which of the rechargeable batteries has a lowest charge;

reducing a battery voltage supplied from the plurality of serially connected rechargeable batteries; and

supplying a reduced voltage to the lowest charged rechargeable battery.

2. A method of discharging as recited in claim 1, wherein the voltage of each rechargeable battery is measured to determine the remaining charge for each battery, respectively.

3. A method of discharging as recited in claim 1, wherein the serially connected rechargeable batteries are individually charged to full capacity in sequence.

4. A method of discharging as recited in claim 1, further comprising:

converting the output voltage from the plurality of serially connected rechargeable batteries into to a battery charging voltage via a DC/DC converter.

5. A method of discharging as recited in claim 4, wherein the DC/DC converter provides an output voltage that is varied depending on the remaining battery charge of the lowest charged rechargeable battery.

6. A method of discharging as recited in claim 4, wherein the DC/DC converter provides an output voltage that is a fixed voltage.

7. A method of discharging as recited in claim 4, wherein DC/DC converter provides an output voltage that is capable of charging the lowest charged rechargeable battery.

8. A method of discharging as recited in claim 4, wherein DC/DC converter provides an output voltage that is capable of reducing a discharge current of the lowest charged rechargeable battery without recharging the lowest charged rechargeable battery.

9. A method of discharging as recited in claim 4, wherein DC/DC converter provides an output voltage that is incapable of charging the lowest charged rechargeable battery, but is capable of eliminating discharge current of the lowest charged rechargeable battery.

10. A method of discharging as recited in claim 4, further comprising:

raising the DC/DC converter output voltage when the remaining charge of the lowest charged rechargeable battery decreases; and

lowering the DC/DC converter output voltage when remaining charge of the lowest charged rechargeable battery increases.

11. A method of discharging and charging a plurality of serially connected rechargeable batteries comprising:

discharging an output voltage from the plurality of serially connected rechargeable batteries into a load;

measuring remaining charge in each rechargeable battery being discharged;

converting the output voltage from the plurality of serially connected rechargeable batteries into a battery charging voltage via a DC/DC converter;

determining which of the plurality of rechargeable batteries have a charge that is below a predetermined amount; and

charging the plurality of rechargeable batteries that have a charge that is below the predetermined amount with a DC/DC converter output.

12. A battery assembly which supplies power to a load, said battery assembly comprising:

a plurality of serially connected rechargeable batteries, each rechargeable battery having a positive and negative terminal, respectively;

a discharge control circuit to control the state of rechargeable battery discharge, said discharge control circuit comprising;

a remaining battery capacity detection circuit to measure the remaining charge of each rechargeable battery and determine which rechargeable battery of the plurality of serially connected rechargeable batteries has the lowest charge,

a DC/DC converter to convert an output voltage from the plurality of serially connected rechargeable batteries to a reduced battery voltage, the DC/DC converter having positive and negative output terminals, and

switching circuitry to supply the reduced battery voltage to the rechargeable battery of the plurality of serially connected rechargeable batteries that has the lowest charge;

wherein the discharge control circuit is operable to discharge the plurality of serially connected rechargeable batteries, while output from the plurality of serially connected rechargeable batteries is converted to a battery voltage by the DC/DC converter; and

wherein the discharge control circuit is operable to supply the reduced battery voltage to the rechargeable battery determined to have the lowest charge by the remaining battery capacity detection circuit.

13. A battery assembly as recited in claim 12, wherein the DC/DC converter is operable to output voltage depending on the remaining charge of the rechargeable battery of the plurality of serially connected rechargeable batteries that has the lowest charge.

14. A battery assembly as recited in claim 12, wherein DC/DC converter output voltage is a fixed voltage.

15. A battery assembly as recited in claim 12, wherein DC/DC converter is operable to output a voltage that is capable of charging the rechargeable battery of the plurality of serially connected rechargeable batteries that has the lowest charge.

16. A battery assembly as recited in claim 12,

wherein DC/DC converter is operable to output a voltage that is incapable of charging the rechargeable battery of the plurality of serially connected rechargeable batteries that has the lowest charge, and

wherein DC/DC converter is operable to output a voltage that is capable of reducing the discharge current of the rechargeable battery of the plurality of serially connected rechargeable batteries that has the lowest charge.

17. A battery assembly as recited in claim 12,

wherein the DC/DC converter is operable to output a voltage that is incapable of charging the rechargeable battery of the plurality of serially connected rechargeable batteries that has the lowest charge, and

wherein the DC/DC converter is operable to output a voltage that is capable of making the discharge current of rechargeable battery of the plurality of serially connected rechargeable batteries that has the lowest charge equal to zero.

18. A battery assembly as recited in claim 12,

wherein the DC/DC converter is operable to output a voltage that increases when the charge of the rechargeable battery of the plurality of serially connected rechargeable batteries that has the lowest charge decreases, and

wherein the DC/DC converter is operable to output a voltage that decreases when the charge of the rechargeable battery of the plurality of serially connected rechargeable batteries that has the lowest charge increases.

19. A battery assembly as recited in claim 12, wherein switching circuitry further comprises switching devices, the switching devices are operable to independently connect positive and negative terminals of each rechargeable battery to positive and negative output terminals of the DC/DC converter.

20. A battery assembly as recited in claim 19, wherein the switching circuitry further comprises protection resistors, the protection resistors being connected in series with the switching devices.

21. A battery assembly which supplies power to a load, said battery assembly comprising:

a plurality of serially connected rechargeable batteries, each rechargeable battery having a positive and negative terminal, respectively;

discharge and charge control circuit to control the state of rechargeable battery discharge, said discharge control circuit comprising;

a remaining battery capacity detection circuit to measure the remaining charge of each rechargeable battery and determine which rechargeable battery of the plurality of serially connected rechargeable batteries has the lowest charge,

a DC/DC converter to convert an output voltage from the plurality of serially connected rechargeable batteries to a reduced battery voltage, the DC/DC converter having positive and negative output terminals,

switching circuitry to supply DC/DC converter output to the rechargeable battery of the plurality of serially connected rechargeable batteries that has the lowest charge, and

a charging circuit operable to sequentially charge individual serially connected rechargeable batteries to full capacity, respectively;

wherein the discharge control circuit is operable to discharge the plurality of serially connected rechargeable batteries, while output from the plurality of serially connected rechargeable batteries is converted to a battery voltage by the DC/DC converter; and

wherein the discharge control circuit is operable to supply the reduced battery voltage to the rechargeable battery determined to have the lowest charge by the remaining battery capacity detection circuit.