System and method for balancing charge cycles for batteries or multiple-cell battery packs

• US 5,920,179 A
• Filed: 05/05/1997
• Issued: 07/06/1999
• Est. Priority Date: 05/05/1997
• Status: Expired due to Fees

• Current Assignee: AER Energy Resources, Inc.
• Original Assignee: AER Energy Resources, Inc.
• Inventors: Pedicini, Christopher S.
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): TOATLEY, GREGORY J
• Application Number:
  US08/851,419
• Time in Patent Office: 792 Days
• Field of Search: 320/128, 320/138, 320/136, 320/134, 320/160, 320/122, 320/118, 320/119
• US Class Current: 320/122
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits

Abstract

A charging system and method are disclosed that provide balanced charge cycles for batteries or multiple-cell battery packs by using a controller, a charging source gate, multiple adjustable shunting devices and multiple charge monitors. During a virgin charge cycle, the controller adjusts each of the adjustable shunting devices to provide a maximum charging current, opens the charging source gate, and then monitors the charge level of each of the battery cells. When the voltage potential of one of the battery cells reaches a threshold value, the charge source gate is closed to disable the charging current, and the fully charged battery cell is identified. The controller then determines a shunt value for adjusting the adjustable shunting device connected to the fully charged battery cell and uses this shunt value on the next charge cycle. Each subsequent charge cycle results in a different battery cell becoming fully charged and then the recalculation of a shunt value. The overall effect is to allow each battery or each cell of a battery pack to be periodically fully charged, regardless of the variations in the charging, discharging and efficiency characteristics of the batteries or battery cells.

Claims

1. A method for balancing the charge cycles for a plurality of battery units, comprising the steps of:

(a) initiating a charge cycle for simultaneously charging a plurality of battery units at an initial charging rate;

(b) detecting a triggering battery unit, the triggering battery unit being the first battery unit to be charged to a threshold level;

(c) terminating the charge cycle;

(d) initiating a subsequent charge cycle; and

(e) throughout the subsequent charge cycle, reducing the charging rate for the triggering battery unit by a selected amount.

2. A battery unit charging system for providing a balanced charge cycle for a plurality of battery units, comprising:

a controller;

a gating means coupled to the controller for enabling the input of a current;

a shunting means for receiving the current and in response to input received from the controller, dividing the current between a charge output for driving a terminal of a battery unit, and a shunt output;

a monitoring means for monitoring the charge level of each battery unit;

the controller, being operative to;

(a) initialize the shunting means to divide the current by a first amount between the charge outputs for each of the battery units and the shunt outputs;

(b) enable the gating means to provide the current to the shunting means for simultaneously charging a plurality of battery units;

(c) detect a triggering battery unit, the triggering battery unit being the first battery unit that the monitoring means identifies as charging to a threshold level;

(d) disable the gating means; and

(e) identify a second amount for the shunting means to divide the current between the charge output and shunt output associated with the triggering battery unit during a next charge cycle.

3. The battery unit charging system of claim 2, wherein each battery unit is a single battery cell.

4. The battery unit charging system of claim 2, wherein each battery unit is a single battery having one or more cells.

5. A charging system for providing a balanced charge cycle for battery packs containing multiple battery units, comprising:

a controller;

a current source gate coupled to the controller for enabling the input of a charging current from a charging source;

a plurality of adjustable shunting devices, each adjustable shunting device being coupled to the controller and the charging source gate, having a charge output connectable to a terminal of a battery unit, and having a shunt output functionally connected to the charging source;

a plurality of charge monitors, each charge monitor being coupled to the controller and being connectable across the terminals of a battery unit for measuring the charge of the battery unit;

the controller, being operative to;

(a) initiate a virgin charge cycle by adjusting each of the adjustable shunting devices in order to maximize the charge output to a connected battery unit, and enabling the input of the charging current by opening the charging source gate;

(b) identify a triggering battery unit by monitoring each of the charge monitors until the charge of one of the battery units reaches a threshold value;

(c) in response to identifying a triggering battery unit, close the charging source gate to disable the charging current; and

(d) determine a shunt value for the adjustable shunting device connected to the triggering battery unit to be used during a subsequent, shunted charge cycle.

6. The charging system of claim 5, wherein the controller is further operative to:

initiate the shunted charge cycle by adjusting the adjustable shunting device connected to the triggering battery unit in accordance with the shunt value, adjusting each of the adjustable shunting devices connected to the non-triggering battery units in order to maximize the charge output, and enabling the input of the charging source by opening the charging source gate;

identify a new triggering battery unit by monitoring each of the charge monitors until the charge of one of the battery units reaches a threshold value;

in response to identifying a new triggering battery unit, close the charging source gate to disable the charging current; and

determine a new shunt value for the adjustable shunting device connected to the new triggering battery unit to be used during a subsequent, shunted charge cycle.

7. The charging system of claim 6, wherein the controller is operative to determine a shunt value by selecting a shunt value that limits the shunt output of the adjustable shunting devices within a range including 1% to 5% of the maximum charge output.

8. The charging system of claim 6, wherein the controller, the charging source gate, the adjustable shunting devices, and the charger monitors are all incorporated into a single battery pack.

9. The charging system of claim 8, wherein the battery units are single metal-air battery cells.

10. The charging system of claim 6, wherein the battery units are single metal-air battery cells.

11. The charging system of claim 5, wherein the controller is operative to determine a shunt value by selecting a shunt value to limit the shunt output of the adjustable shunting devices within a range including 1% to 5% of the maximum charging output.

12. A charging system for providing a balanced charge cycle for battery units, comprising:

a controller with a memory storage device;

a current source gate coupled to the controller for enabling the input of a charging current from a charging source;

a plurality of adjustable shunting devices, each adjustable shunting device being coupled to the controller and the charging source gate, having a charge output connectable to a terminal of a battery unit, and having a shunt output functionally connected to the charging source;

a plurality of charge monitors, each charge monitor being coupled to the controller and being connectable across the terminals of a battery unit for measuring the voltage potential of the battery unit;

the controller, being operative to;

set a shunt value variable in the memory storage device for each adjustable shunting device to a minimum value; and

for each requested charge cycle;

adjust each of the adjustable shunting devices in accordance with the shunt value variable;

enable the input of the charging current by opening the charging source gate;

identify a triggering battery unit by monitoring each of the charge monitors until the voltage potential of one of the battery units reaches a threshold value;

in response to identifying a triggering battery unit, disable the charging current by closing the charging source gate;

determine a shunt value for the adjustable shunting device connected to the triggering battery unit; and

store the shunt value into the shunt value variable of the memory storage device corresponding with the triggering battery unit.

13. The charging system of claim 12, wherein the controller is further operative to reset the shunt value variables to the minimum value when one of the shunt value variables reaches a maximum value.

14. The charging system of claim 12, wherein the controller is operative to determine a shunt value by selecting a shunt value that limits the shunt output of the adjustable shunting devices within a range including 1% to 5% of the maximum charge output.

15. The charging system of claim 12, wherein the controller is operative to determine a shunt value by incrementing the current shunt value by a predetermined amount.

16. The charging system of claim 12, wherein the controller, the charging source gate, the adjustable shunting devices, and the charger monitors are all incorporated into a single battery pack.

17. The charging system of claim 12, wherein the battery units are single metal-air battery cells.

18. A method for balancing the charge cycles for a plurality of battery units, comprising the steps of:

in response to receiving a first charge request, initiating a virgin charge cycle, the virgin charge cycle allowing a maximum charge current to be provided to each of the battery units;

terminating the virgin charge cycle when the voltage potential of a first triggering battery unit reaches a threshold value;

determining a first shunt value for the first triggering battery unit;

in response to receiving a second charge request, initiating a first shunted charge cycle, the first shunted charge cycle allowing a maximum charge current to be provided to each of the non-triggering battery units, and a charge current shunted in accordance with the shunt value to be provided to the first triggering battery unit;

terminating the first shunted charge cycle when the voltage potential of a second triggering battery unit reaches the threshold value;

determining a second shunt value for the second triggering battery unit; and

in response to receiving a third charge request, initiating a second shunted charge cycle, the second shunted charge cycle allowing a maximum charge current to be provided to each of the non-triggering battery units, and a charge current shunted in accordance with the second shunt value to be provided to the second triggering battery unit.

19. The method of claim 18, wherein the step of determining a shunt value for a triggering battery unit comprises the steps of:

examining the charge level of at least one other battery unit; and

selecting a shunt value that ensures at least one other battery unit will charge to the threshold value on a subsequent charge cycle prior to the triggering battery unit charging to the threshold value.

20. The method of claim 18, wherein the step of determining a shunt value for the triggering battery unit comprises the steps of:

examining the voltage potential of at least one other battery unit;

selecting a shunt value based on the examined voltage potentials that ensures at least one other battery unit will charge to the threshold value on a subsequent charge cycle prior to the triggering battery unit charging to the threshold value; and

limiting the shunt value to include the range of 1% to 5% of the maximum charge current.

21. The method of claim 18, wherein the step of determining a shunt value for the triggering battery unit comprises the step of setting the shunt value to a fixed value in the range of 1% to 5% of the maximum charge current.

22. A method for balancing the charge cycles for a plurality of battery units, comprising the steps of:

(a) assigning an initial shunt value to each of a plurality of adjustable shunting devices, each adjustable shunting device being associated with one of a plurality of battery units, the initial shunt value being selected to maximum charge current passed to each of the battery units through the adjustable shunting device associated with the battery unit;

(b) activating a charge cycle by enabling a charge current to be provided to the each of the battery units through the adjustable shunting device associated with the battery unit;

(c) terminating the active charge cycle when the charge of a first battery unit reaches a threshold value, and identifying the first battery unit as an active triggering battery unit; and

(d) for each subsequent charge cycle;

determining a new shunt value for the active triggering battery unit;

adjusting the adjustable shunting device associated with the active triggering battery unit in accordance with the new shunt value; and

terminating the charge cycle when a next battery unit is charged to a threshold value, and identifying the next battery unit as the active triggering battery unit.

23. The method of claim 22, wherein the step of determining an active shunt value comprises the step of incrementing the shunt value by a predetermined amount.

24. A charging system for providing a balanced charge cycle for battery units, comprising:

a controller with a memory storage device;

a current source gate coupled to the controller for enabling the input of a charging current from a charging source;

a plurality of adjustable shunting, devices, each adjustable shunting device being coupled to the controller and the charging source gate, having a charge output connectable to a terminal of a battery unit, and having a shunt output functionally connected to the charging source;

a plurality of charge monitors, each charge monitor being coupled to the controller and being connectable across the terminals of a battery unit for measuring the voltage potential of the battery unit;

the controller, being operative to;

set a shunt value variable in the memory storage device for each adjustable shunting device to a minimum value; and

for each requested charge cycle;

adjust each ol the adjustable shunting devices in accordance with the shunt value variable;

enable the input of the charging current by opening the charging source gate;

identify a triggering battery unit by monitoring each of the charge monitors until the voltage potential of one of the battery units reaches a threshold value;

in response to identifying a triggering battery unit, disable the charging current by closing the charging source gate;

determine a shunt value for the adjustable shunting device connected to the triggering battery unit by examining the voltage potential of at least one other battery unit and selecting a shunt value that ensures at least one other battery unit will charge to the threshold value prior to the triggering battery unit.; and

store the shunt value into the shunt value variable of the memory storage device corresponding with the triggering battery unit.

25. A method for balancing the charge cycles for a plurality of battery units, comprising the steps of:

(a) assigning an initial shunt value to each of a plurality of adjustable shunting devices, each adjustable shunting device being associated with one of a plurality of battery units, the initial shunt value being selected to maximum charge current passed to each of the battery units through the adjustable shunting device associated with the battery unit;

(b) activating a charge cycle by enabling a charge current to be provided to the each of the battery units through the adjustable shunting device associated with the battery unit;

(c) terminating the active charge cycle when the charge of a first battery unit reaches a threshold value, and identifying the first battery unit as an active triggering battery unit; and

(d) for each subsequent charge cycle;

determining a new shunt value for the active triggering battery unit by examining the voltage potential of each battery unit and selecting a new shunt value as a function of these voltage potentials and that will allow at least one other battery unit to charge to the threshold value prior to the triggering battery unit;

adjusting the adjustable shunting device associated with the active triggering battery unit in accordance with the new shunt value; and

terminating the charge cycle when a next battery unit is charged to a threshold value, and identifying the next battery unit as the active triggering battery unit.