Equalization of series-connected cells of a battery using controlled charging and discharging pulses

• US 5,889,385 A
• Filed: 08/19/1997
• Issued: 03/30/1999
• Est. Priority Date: 08/19/1997
• Status: Expired due to Fees

• Current Assignee: Advanced Charger Technology, Inc.
• Original Assignee: Advanced Charger Technology, Inc.
• Inventors: Podrazhansky, Mikhail M., Podrazhansky, Yury M., Kusharskiy, Yefim Y.
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): TOATLEY, GREGORY J
• Application Number:
  US08/914,674
• Time in Patent Office: 588 Days
• Field of Search: 320/130, 320/129, 320/132, 320/133, 320/188, 320/119, 320/139, 320/151, 320/152, 320/153, 320/160, 320/162
• US Class Current: 320/130
• CPC Class Codes: H02J 7/0014 Circuits for equalisation of charge between batteries
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: H02J 7/0049 Detection of fully charged condition
• CPC Class Codes: H02J 7/00711 with introduction of pulses during the charging process

Abstract

A charge pulse (200A) is applied to the battery (B). The open circuit voltage of each cell (C1-CN) is then measured during a first rest period (210A). A depolarization pulse (220A) is then applied to the battery. The open circuit voltage of each cell is then measured during a second rest period (210B). The open circuit voltages for the first and second rest periods for each cell are compared to yield a voltage difference (DELTA Y). This voltage difference is then compared with a threshold voltage (V THRESHOLD). If the voltage difference is greater than the threshold voltage then the cell is being charged too rapidly, or is being overcharged, so one or more of the charge cycle parameters are adjusted. Some of the charge cycle parameters are, for example, the charge pulse current amplitude, the charge pulse duration, the number of consecutive charge pulses, the depolarization pulse current amplitude, the depolarization pulse duration, the number of consecutive depolarization pulses, the duration of the rest periods, or a combination of these. Multiple charge pulses (200A, 200B) and depolarization pulses (220A, 220B, 220C) may also be used. These parameters may be adjusted for the battery as a whole and/or for each cell individually. The adjustment to the charge cycle parameters may also be made on a "worst case" or a "best case" cell basis, with this cell controlling the charge cycle parameters for all the cells. Several techniques for adjusting the charge cycle parameters are disclosed.

Claims

1. A method for equalizing the charge among a plurality of series-connected energy storage devices in a set of said energy storage devices, comprising the steps of:

applying at least one charging pulse to said set, said charging pulse providing a series charging current, said series charging current having an amplitude and a duration, each said energy storage device receiving a portion of said charging pulse which is independent of a portion of said charging pulse received by any other energy storage device;

applying a plurality of depolarization pulses to said set, said depolarization pulses each drawing a discharge current having an amplitude and a duration, said depolarization pulses being separated from each other by rest periods, each said rest period having a duration;

for each said energy storage device, measuring the voltage of said energy storage device at a predetermined point within a said rest period preceding a predetermined said depolarization pulse;

for each said energy storage device, measuring the voltage of said energy storage device at a predetermined point within a said rest period following said predetermined depolarization pulse;

for each said energy storage device, determining a voltage difference between said voltage at said predetermined point within said preceding rest period and said voltage at said predetermined point within said following rest period;

comparing each said voltage difference with a threshold voltage;

if any of said voltage differences is greater than said threshold voltage then performing at least one of the following;

decreasing said amplitude of said series charging current, decreasing said duration of said series charging current, decreasing a number of said charging pulses which occur without an intervening said depolarization pulse, increasing said duration of at least one said rest period, increasing said amplitude of said discharge current, increasing said duration of said discharge current, or increasing a number of said depolarization pulses which occur without an intervening said charging pulse;

for at least one said energy storage device which has a said voltage difference greater than said threshold voltage, performing at least one of the following;

decreasing said amplitude of said portion of said series charging current received by said energy storage device, decreasing said duration of said portion of said series charging current received by said energy storage device, or decreasing a number of said charging pulses of said portion of said series charging current received by said energy storage device which occur without an intervening said depolarization pulse; and

repeating the above steps.

12. The method of any one of claims 1-11, and further comprising the steps of:

measuring the temperature of each said energy storage device;

determining a threshold voltage for each said energy storage device based upon said temperature of said energy storage device; and

wherein

said step of comparing each said voltage difference with a threshold voltage comprises comparing said voltage difference for said energy storage device with said threshold voltage determined by said temperature of said energy storage device.

13. The method of any one of claims 1-11, and further comprising the steps of:

measuring the temperature of said set of energy storage devices;

determining a threshold voltage based upon said temperature of said set of energy storage devices; and

wherein

said step of comparing each said voltage difference with a threshold voltage comprises comparing said voltage difference for said energy storage devices with said threshold voltage determined by said temperature of said set of energy storage devices.

2. A method for equalizing the charge among a plurality of series-connected energy storage devices in a set of said energy storage devices, comprising the steps of:

applying at least one charging pulse to said set, said charging pulse providing a series charging current, said series charging current having an amplitude and a duration;

applying a plurality of depolarization pulses to said set, said depolarization pulses each drawing a discharge current having an amplitude and a duration, said depolarization pulses being separated from each other by rest periods, each said rest period having a duration;

for each said energy storage device, measuring the voltage of said energy storage device at a predetermined point within a said rest period preceding a predetermined said depolarization pulse;

applying a specific depolarization pulse to at least one said energy storage device during at least one of said depolarization pulses applied to said set, a said specific depolarization pulse drawing an additional discharge current having an amplitude and a duration from said energy storage device to which it is applied;

for each said energy storage device, measuring the voltage of said energy storage device at a predetermined point within a said rest period following said predetermined depolarization pulse;

for each said energy storage device, determining a voltage difference between said voltage at said predetermined point within said preceding rest period and said voltage at said predetermined point within said following rest period;

comparing each said voltage difference with a threshold voltage;

if any of said voltage differences is greater than said threshold voltage then performing at least one of the following;

decreasing said amplitude of said series charging current, decreasing said duration of said series charging current, decreasing a number of said charging pulses which occur without an intervening said depolarization pulse, increasing said duration of at least one said rest period, increasing said amplitude of said discharge current, increasing said duration of said discharge current, or increasing a number of said depolarization pulses which occur without an intervening said charging pulse;

for at least one said energy storage device which has a said voltage difference greater than said threshold voltage, performing at least one of the following;

increasing said amplitude of said discharge current specific depolarization pulse, increasing said duration of said discharge current specific depolarization pulse, or increasing a number of said specific depolarization pulses which occur without an intervening said charging pulse; and

repeating the above steps.

3. A method for equalizing the charge among a plurality of series-connected energy storage devices in a set of said energy storage devices, comprising the steps of:

applying at least one charging pulse to said set, said charging pulse providing a series charging current, said series charging current having an amplitude and a duration, each said energy storage device receiving a portion of said charging pulse which is independent of a portion of said charging pulse received by any other energy storage device;

applying a plurality of depolarization pulses to said set, said depolarization pulses each drawing a discharge current having an amplitude and a duration, said depolarization pulses being separated from each other by rest periods, each said rest period having a duration;

for each said energy storage device, measuring the voltage of said energy storage device at a predetermined point within a said rest period preceding a predetermined said depolarization pulse;

for each said energy storage device, measuring the voltage of said energy storage device at a predetermined point within a said rest period following said predetermined depolarization pulse;

for each said energy storage device, determining a voltage difference between said voltage at said predetermined point within said preceding rest period and said voltage at said predetermined point within said following rest period;

comparing each said voltage difference with a threshold voltage;

for at least one said energy storage device which has a said voltage difference greater than said threshold voltage, performing at least one of the following;

decreasing said amplitude of said portion of said series charging current received by said energy storage device, decreasing said duration of said portion of said series charging current received by said energy storage device, or decreasing a number of said charging pulses of said portion of said series charging current received by said energy storage device which occur without an intervening said depolarization pulse; and

repeating the above steps.

4. A method for equalizing the charge among a plurality of series-connected energy storage devices in a set of said energy storage devices, comprising the steps of:

applying at least one charging pulse to said set, said charging pulse providing a series charging current, said series charging current having an amplitude and a duration;

applying a plurality of depolarization pulses to said set, said depolarization pulses each drawing a discharge current having an amplitude and a duration, said depolarization pulses being separated from each other by rest periods, each said rest period having a duration;

for each said energy storage device, measuring the voltage of said energy storage device at a predetermined point within a said rest period preceding a predetermined said depolarization pulse;

for each said energy storage device, measuring the voltage of said energy storage device at a predetermined point within a said rest period following said predetermined depolarization pulse;

applying a specific depolarization pulse to at least one said energy storage device during at least one of said depolarization pulses applied to said set, a said specific depolarization pulse drawing an additional discharge current having an amplitude and a duration from said energy storage device to which it is applied;

for each said energy storage device, determining a voltage difference between said voltage at said predetermined point within said preceding rest period and said voltage at said predetermined point within said following rest period;

comparing each said voltage difference with a threshold voltage;

for at least one said energy storage device which has a said voltage difference greater than said threshold voltage, performing at least one of the following;

increasing said amplitude of said discharge current specific depolarization pulse, increasing said duration of said discharge current specific depolarization pulse, or increasing a number of said specific depolarization pulses which occur without an intervening said charging pulse; and

repeating the above steps.

5. A method for equalizing the charge among a plurality of series-connected energy storage devices in a set of said energy storage devices, comprising the steps of:

applying at least one charging pulse to said set, said charging pulse providing a series charging current, said series charging current having an amplitude and a duration, each said energy storage device receiving a portion of said charging pulse which is independent of a portion of said charging pulse received by any other energy storage device;

applying a plurality of depolarization pulses to said set, said depolarization pulses each drawing a discharge current having an amplitude and a duration, said depolarization pulses being separated from each other by rest periods, each said rest period having a duration;

for each said energy storage device, measuring the voltage of said energy storage device at a predetermined point within a said rest period preceding a predetermined said depolarization pulse;

for each said energy storage device, measuring the voltage of said energy storage device at a predetermined point within a said rest period following said predetermined depolarization pulse;

applying a specific depolarization pulse to at least one said energy storage device during at least one of said depolarization pulses applied to said set, a said specific depolarization pulse drawing an additional discharge current having an amplitude and a duration from said energy storage device to which it is applied;

for each said energy storage device, determining a voltage difference between said voltage at said predetermined point within said preceding rest period and said voltage at said predetermined point within said following rest period;

comparing each said voltage difference with a threshold voltage;

for at least one said energy storage device which has a said voltage difference greater than said threshold voltage, performing at least one of the following;

decreasing said amplitude of said portion of said series charging current received by said energy storage device, decreasing said duration of said portion of said series charging current received by said energy storage device, decreasing a number of said charging pulses of said portion of said series charging current received by said energy storage device which occur without an intervening said depolarization pulse, increasing said amplitude of said discharge current specific depolarization pulse, increasing said duration of said discharge current specific depolarization pulse, or increasing a number of said specific depolarization pulses which occur without an intervening said charging pulse; and

repeating the above steps.

6. A method for equalizing the charge among a plurality of series-connected energy storage devices in a set of said energy storage devices, comprising the steps of:

applying at least one charging pulse to said set, said charging pulse providing a series charging current, said series charging current having an amplitude and a duration;

applying a plurality of depolarization pulses to said set, said depolarization pulses each drawing a discharge current having an amplitude and a duration, said depolarization pulses being separated from each other by rest periods, each said rest period having a duration;

for each said energy storage device, measuring the voltage of said energy storage device at a predetermined point within a said rest period preceding a predetermined said depolarization pulse;

for each said energy storage device, measuring the voltage of said energy storage device at a predetermined point within a said rest period following said predetermined depolarization pulse;

for each said energy storage device, determining a voltage difference between said voltage at said predetermined point within said preceding rest period and said voltage at said predetermined point within said following rest period;

comparing each said voltage difference with a threshold voltage;

if none of said voltage differences is greater than said threshold voltage then performing at least one of the following;

increasing said amplitude of said series charging current, increasing said duration of said series charging current, increasing a number of said charging pulses which occur without an intervening said depolarization pulse, decreasing said duration of at least one said rest period, decreasing said amplitude of said discharge current, decreasing said duration of said discharge current, or decreasing a number of said depolarization pulses which occur without an intervening said charging pulse; and

repeating the above steps.

7. A method for equalizing the charge among a plurality of series-connected energy storage devices in a set of said energy storage devices, comprising the steps of:

applying at least one charging pulse to said set, a said charging pulse providing a series charging current, said series charging current having an amplitude and a duration, each said energy storage device receiving a portion of said charging pulse which is independent of a portion of said charging pulse received by any other energy storage device;

applying a plurality of depolarization pulses to said set, said depolarization pulses each drawing a discharge current having an amplitude and a duration, said depolarization pulses being separated from each other by rest periods, each said rest period having a duration;

for each said energy storage device, measuring the voltage of said energy storage device at a predetermined point within a said rest period preceding a predetermined said depolarization pulse;

for each said energy storage device, measuring the voltage of said energy storage device at a predetermined point within a said rest period following said predetermined depolarization pulse;

for each said energy storage device, determining a voltage difference between said voltage at said predetermined point within said preceding rest period and said voltage at said predetermined point within said following rest period;

comparing each said voltage difference with a threshold voltage;

if none of said voltage differences is greater than said threshold voltage then performing at least one of the following;

increasing said amplitude of said series charging current, increasing said duration of said series charging current, increasing a number of said charging pulses which occur without an intervening said depolarization pulse, decreasing said duration of at least one said rest period, decreasing said amplitude of said discharge current, decreasing said duration of said discharge current, or decreasing a number of said depolarization pulses which occur without an intervening said charging pulse;

for at least one said energy storage device which has a said voltage difference greater than said threshold voltage, performing at least one of the following;

decreasing said amplitude of said portion of said series charging current received by said energy storage device, decreasing said duration of said portion of said series charging current received by said energy storage device, or decreasing a number of said charging pulses of said portion of said series charging current received by said energy storage device which occur without an intervening said depolarization pulse; and

repeating the above steps.

8. A method for equalizing the charge among a plurality of series-connected energy storage devices in a set of said energy storage devices, comprising the steps of:

applying at least one charging pulse to said set, said charging pulse providing a series charging current, said series charging current having an amplitude and a duration;

applying a plurality of depolarization pulses to said set, said depolarization pulses each drawing a discharge current having an amplitude and a duration, said depolarization pulses being separated from each other by rest periods, each said rest period having a duration;

for each said energy storage device, measuring the voltage of said energy storage device at a predetermined point within a said rest period preceding a predetermined said depolarization pulse;

for each said energy storage device, measuring the voltage of said energy storage device at a predetermined point within a said rest period following said predetermined depolarization pulse;

applying a specific depolarization pulse to at least one said energy storage device during at least one of said depolarization pulses applied to said set, a said specific depolarization pulse drawing an additional discharge current having an amplitude and a duration from said energy storage device to which it is applied;

for each said energy storage device, determining a voltage difference between said voltage at said predetermined point within said preceding rest period and said voltage at said predetermined point within said following rest period;

comparing each said voltage difference with a threshold voltage;

if none of said voltage differences is greater than said threshold voltage then performing at least one of the following;

increasing said amplitude of said series charging current, increasing said duration of said series charging current, increasing a number of said charging pulses which occur without an intervening said depolarization pulse, decreasing said duration of at least one said rest period, decreasing said amplitude of said discharge current, decreasing said duration of said discharge current, or decreasing a number of said depolarization pulses which occur without an intervening said charging pulse;

for at least one said energy storage device, performing at least one of the following;

increasing said amplitude of said discharge current specific depolarization pulse, increasing said duration of said discharge current specific depolarization pulse, or increasing a number of said specific depolarization pulses which occur without an intervening said charging pulse; and

repeating the above steps.

9. A method for equalizing the charge among a plurality of series-connected energy storage devices in a set of said energy storage devices, comprising the steps of:

applying at least one charging pulse to said set, said charging pulse providing a series charging current, said series charging current having an amplitude and a duration, each said energy storage device receiving a portion of said charging pulse which is independent of a portion of said charging pulse received by any other energy storage device;

applying a plurality of depolarization pulses to said set, said depolarization pulses each drawing a discharge current having an amplitude and a duration, said depolarization pulses being separated from each other by rest periods, each said rest period having a duration;

for each said energy storage device, measuring the voltage of said energy storage device at a predetermined point within a said rest period preceding a predetermined said depolarization pulse;

for each said energy storage device, measuring the voltage of said energy storage device at a predetermined point within a said rest period following said predetermined depolarization pulse;

for each said energy storage device, determining a voltage difference between said voltage at said predetermined point within said preceding rest period and said voltage at said predetermined point within said following rest period;

comparing each said voltage difference with a threshold voltage;

for at least one said energy storage device which has a voltage difference less than said threshold voltage, performing at least one of the following;

increasing said amplitude of said portion of said series charging current received by said energy storage device, increasing said duration of said portion of said series charging current received by said energy storage device, or increasing a number of said charging pulses of said portion of said series charging current received by said energy storage device which occur without an intervening said depolarization pulse; and

repeating the above steps.

10. A method for equalizing the charge among a plurality of series-connected energy storage devices in a set of said energy storage devices, comprising the steps of:

applying at least one charging pulse to said set, said charging pulse providing a series charging current, said series charging current having an amplitude and a duration;

applying a plurality of depolarization pulses to said set, said depolarization pulses each drawing a discharge current having an amplitude and a duration, said depolarization pulses being separated from each other by rest periods, each said rest period having a duration;

for each said energy storage device, measuring the voltage of said energy storage device at a predetermined point within a said rest period preceding a predetermined said depolarization pulse;

for each said energy storage device, measuring the voltage of said energy storage device at a predetermined point within a said rest period following said predetermined depolarization pulse;

applying a specific depolarization pulse to at least one said energy storage device during at least one of said depolarization pulses applied to said set, a said specific depolarization pulse drawing an additional discharge current having an amplitude and a duration from said energy storage device to which it is applied;

for each said energy storage device, determining a voltage difference between said voltage at said predetermined point within said preceding rest period and said voltage at said predetermined point within said following rest period;

comparing each said voltage difference with a threshold voltage;

for at least one said energy storage device which has a voltage difference less than said threshold voltage, performing at least one of the following;

decreasing said amplitude of said discharge current specific depolarization pulse, decreasing said duration of said discharge current specific depolarization pulse, or decreasing a number of said specific depolarization pulses which occur without an intervening said charging pulse; and

repeating the above steps.

11. A method for equalizing the charge among a plurality of series-connected energy storage devices in a set of said energy storage devices, comprising the steps of:

applying at least one charging pulse to said set, said charging pulse providing a series charging current, said series charging current having an amplitude and a duration, each said energy storage device receiving a portion of said charging pulse which is independent of a portion of said charging pulse received by any other energy storage device;

applying a plurality of depolarization pulses to said set, said depolarization pulses each drawing a discharge current having an amplitude and a duration, said depolarization pulses being separated from each other by rest periods, each said rest period having a duration;

for each said energy storage device, measuring the voltage of said energy storage device at a predetermined point within a said rest period preceding a predetermined said depolarization pulse;

for each said energy storage device, measuring the voltage of said energy storage device at a predetermined point within a said rest period following said predetermined depolarization pulse;

applying a specific depolarization pulse to at least one said energy storage device during at least one of said depolarization pulses applied to said set, a said specific depolarization pulse drawing an additional discharge current having an amplitude and a duration from said energy storage device to which it is applied;

for each said energy storage device, determining a voltage difference between said voltage at said predetermined point within said preceding rest period and said voltage at said predetermined point within said following rest period;

comparing each said voltage difference with a threshold voltage;

for at least one said energy storage device which has a voltage difference less than said threshold voltage, performing at least one of the following;

increasing said amplitude of said portion of said series charging current received by said energy storage device, increasing said duration of said portion of said series charging current received by said energy storage device, increasing a number of said charging pulses of said portion of said series charging current received by said energy storage device which occur without an intervening said depolarization pulse, decreasing said amplitude of said discharge current specific depolarization pulse, decreasing said duration of said discharge current specific depolarization pulse, or decreasing a number of said specific depolarization pulses which occur without an intervening said charging pulse; and

repeating the above steps.