Battery charging method with stepped current profile with operating parameter compensation and associated charger

• US 5,633,576 A
• Filed: 11/21/1994
• Issued: 05/27/1997
• Est. Priority Date: 01/19/1993
• Status: Expired due to Fees

• Current Assignee: Electro Dynamics, Inc.
• Original Assignee: Premier Engineered Products, Inc.
• Inventors: Rose, Jeffrey A., Rose, Stephen D., Cates, Joseph A.
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): TOATLEY, GREGORY J
• Application Number:
  US08/342,526
• Time in Patent Office: 918 Days
• Field of Search: 320/21, 320/22, 320/30, 320/23, 320/20, 320/39, 320/31
• US Class Current: 320/160
• CPC Class Codes: H02J 7/007184 in response to battery voltage gradient

Abstract

A method and apparatus is provided to charge a battery including a DC charge current supply having a variable output. The charging current is varied in accordance with several sensed parameters in the circuit so that battery voltage is accurately controlled. Initially, constant charging current is applied, and upon detecting that battery voltage increases to the gassing voltage, an incremental step reduction in charging current is triggered. The step reduction causes a decrease in battery voltage, dropping it below the gassing voltage. The step reduced charging current is then applied to increase battery voltage back up to the gassing voltage, thereby triggering another step reduction in charging current. This process is repeated multiple times providing a stepped current profile, i.e., each battery voltage increase to the gassing voltage triggering a step reduction in charging current, and in turn a corresponding voltage reduction. The battery voltage, with the alternating increases and decreases, is thus defined by a saw-tooth profile with peaks at the gassing voltage. When the charging current is finally reduced to a minimum level, the sensed battery voltage triggers a termination of the stepped current reduction. Upon the battery reaching full charge, the application of charging current is terminated. In the alternative embodiment, the slope of the voltage curve is detected and analyzed to control a step up profile of the current during the initial phase of charging. The rising temperature of the battery controls a decrease in the gassing or target voltage.

Claims

1. A method of charging a battery utilizing a variable charge current supply comprising the steps of:

applying a charging current to the battery from said charge current supply;

sensing battery voltage;

reducing said charging current when said battery voltage equals a target voltage such that said reduction in said charging current causes a decrease in said battery voltage;

maintaining said battery voltage not greater than said target voltage during said applying and reducing steps;

monitoring change in an operating parameter of the battery during the application of the charging current;

lowering said target voltage in proportion to and to compensate for the change in the parameter being monitored;

repeating said applying and reducing steps to provide a stepped current profile until said charging current is reduced to a minimum value;

continuing the steps of monitoring the operating parameter and lowering the target voltage;

applying said charging current at said minimum value after said reducing step until the battery is at full charge; and

detecting said full charge of the battery, and in response terminating application of said minimum value charging current.

2. The method of charging the battery as set forth in claim 1 wherein the monitoring step of the operating parameter is provided by detecting a rise in operating temperature and the step of reducing the target voltage is proportional to the rise in temperature.

3. The method of charging the battery as set forth in claim 1 wherein the monitoring step of the operating parameter is provided by detecting a rise in operating pressure and the step of reducing the target voltage is proportional to the rise in pressure.

4. The method of charging the battery as set forth in claim 1 wherein is provided the step of analyzing the initial dV/dt where V=battery voltage and T=time during the initial phase of applying said charging current and applying the charging current so as not to exceed the target voltage.

5. The method of charging the battery as set forth in claim 4 wherein in the initial phase, the dV/dt is substantially one and the step up of applying the initial current is less than the rated maximum.

6. The method of charging the battery as set forth in claim 4 wherein is provided stepping up of the current over time from the initial phase to the maximum to reach said target voltage in accordance with the analyzing step and then initiating the step of lowering the battery voltage.

7. The method of charging the battery as set forth in claim 6 wherein is provided the step of modifying the stepping up of the current in response to a substantially instantaneous rise in battery voltage above said target voltage during said initial phase, whereby to assure maintaining said voltage not greater than said target voltage.

8. A battery charger for a DC battery comprising:

means for applying a charging current to said battery;

means for sensing battery voltage;

means for sensing said charging current;

means for monitoring change in an operating parameter of the battery during the application of the charging current;

means for lowering said target voltage in proportion to and to compensate for the change in the parameter being monitored;

means for comparing said battery voltage to the target voltage as said target voltage is being lowered;

means for detecting full charge of the battery;

means to control said charging current in response to input signals from said charging current sensing means, said comparing means, said monitoring means and said full charge detection means.

9. The battery charger as set forth in claim 8 wherein is further provided means associated with said control means for defining a stepped down profile for said charging current to provide a reduction by incremental steps in response to said battery voltage.

10. The battery charger as set forth in claim 8 wherein is further provided means associated with said control means for defining a stepped up profile for said charging current during the initial phase of charging to provide an increase by incremental steps in response to said battery voltage.

11. The battery charger as set forth in claim 10 wherein said means for defining a stepped up profile includes means for analyzing the initial dV/dt where V=battery voltage and T=time.

12. A battery charger for a DC battery comprising:

means for applying a charging current to said battery;

means for sensing a variable parameter including battery voltage;

means for sensing and analyzing the change in said variable parameter;

means for establishing a target voltage for said battery;

means for maintaining said battery voltage not greater than said target voltage;

means for stepping up the charging current during the initial phase of charging in accordance with the change in said variable parameter to provide a stepped current profile until the charging current reaches a maximum value; and

means for applying said charging current until the battery is at full charge.

13. The battery charger as set forth in claim 12 wherein is further provided means for monitoring change in an operating parameter of the battery during the application of the charging current;

means for lowering said target voltage in proportion to and to compensate for the change in the operating parameter being monitored;

means for comparing said battery voltage to the target voltage as it is being lowered; and

means for detecting full charge of the battery.

14. A method of charging a battery utilizing a variable charge current supply comprising the steps of:

applying a charging current to the battery from said charge current supply;

sensing battery voltage;

analyzing the change in battery voltage over time;

establishing a target voltage for said battery;

maintaining said battery voltage not greater than said target voltage;

stepping up the charging current during the initial phase of charging to provide a stepped current profile until the charging current reaches a maximum value;

applying said charging current until the battery is at full charge;

monitoring change in an operating parameter of the battery during the application of the charging current;

lowering said target voltage in proportion to and to compensate for the change in the parameter being monitored;

reducing said charging current by between 0.1-5.0 amps when said battery voltage equals the target voltage such that said reduction in said charging current causes a decrease in said battery voltage;

repeating the steps of applying and reducing the current to provide a stepped down current profile until said charging current is reduced to the minimum value;

continuing the steps of monitoring the operating parameter and lowering the target voltage;

detecting said full charge of the battery; and

initiating a timed sequence of continuing to charge at approximately said minimum value; and

terminating application of said charging current.

15. A method of charging a battery utilizing a variable charge current supply comprising the steps of:

applying a charging current to the battery from said charge current supply;

sensing a variable parameter including battery voltage;

analyzing the change in said variable parameter;

establishing a target voltage for said battery;

maintaining said battery voltage not greater than said target voltage;

stepping up the charging current during the initial phase of charging in accordance with the change in said variable parameter to provide a stepped current profile until the charging current reaches a maximum value;

applying said charging current until the battery is at full charge;

monitoring change in an operating parameter of the battery during the application of the charging current; and

lowering said target voltage in proportion to and to compensate for the change in the operating parameter being monitored.

16. The method of charging the battery as set forth in claim 15 wherein is further provided the steps of reducing the current to provide a stepped down current profile after completion of the initial phase and until said charging current is reduced to the minimum value;

continuing the steps of monitoring the operating parameter and lowering the target voltage;

detecting said substantially full charge of the battery; and

terminating application of said charging current.