Charging system for nickel-zinc batteries

• US 4,503,378 A
• Filed: 05/02/1983
• Issued: 03/05/1985
• Est. Priority Date: 05/02/1983
• Status: Expired due to Fees

• Current Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Jones, Richard A., Reoch, William D.
• Primary Examiner(s): Hickey, R. J.
• Application Number:
  US06/490,425
• Time in Patent Office: 673 Days
• Field of Search: 320/2, 320/3, 320/20, 320/21, 320/39, 320/40
• US Class Current: 320/161
• CPC Class Codes: H02J 7/007184 in response to battery voltage gradient

Abstract

A source of constant current or constant power supplies charging current to a nickel-zinc battery to produce a generally S-shaped battery voltage waveform. To improve battery life, charging is terminated at the inflection point where the slope of the battery voltage changes from increasing to decreasing.

Claims

1. A method of charging a nickel-zinc battery, comprising:

supplying the battery with charging current such that the battery exhibits a charging voltage which increases over time toward a maximum and such that the slope of the charging voltage increases and then decreases as the charging voltage approaches the maximum;

measuring the battery voltage magnitude at predetermined intervals during the entire course of the charging process, and after the occurrence of at least three such intervals determining a slope value at each subsequent interval according to the difference between the most recently measured voltage magnitude and a voltage magnitude measured at least two intervals prior thereto; and

terminating the supply of charging current in substantial relation to the inflection point at which the measured slope values change from increasing to decreasing to thereby improve battery life.

2. A method of charging a nickel-zinc battery, comprising:

supplying the battery charging current such that the battery exhibits a generally S-shaped voltage waveform which increases over time toward a maximum and such that the slope of the voltage waveform increases and then decreases as the charging voltage approaches the maximum;

measuring the battery voltage magnitude at predetermined intervals during the entire course of the charging process and after the occurrence of at least three such intervals determining a slope value at each subsequent interval according to the difference between the most recently measured voltage magnitude and a voltage magnitude measured at least two intervals prior thereto; and

after at least two successive increases in the determined slope value, comparing the most recently determined slope value with previously determined slope values to identify the highest slope value and terminating the supply of charging current when the most recently determined slope value is less than the highest slope value by a least a predetermined amount so as to terminate the charging process in substantial relation to the point at which the slope of the voltage waveform changes from increasing to decreasing thereby improving battery life.

3. Apparatus for charging a nickel-zinc battery, comprising:

means for supplying the battery with charging current such that the battery exhibits a generally S-shaped voltage waveform which increases over time toward a maximum and such that the slope of the voltage waveform increases and then decreases as the charging voltage approaches the maximum;

means for periodically measuring the battery voltage magnitude at predetermined intervals during the entire course of the battery charging process and effective after the occurrence of at least three of such intervals for determining the slope value at each subsequent internal according the difference between the most recently measured voltage magnitude and a voltage magnitude measured at least two intervals prior thereto; and

means effective after such periodically determined slope values have increased at least twice in succession for comparing the most recently determined slope value with the highest determined slope value and for terminating the supply of charging current when the most recently determined slope value falls below the highest determined slope value by at least a predetermined amount so as to terminate the charging process in substantial relation to the point at which the slope of the voltage waveform changes from increasing to decreasing therby improving battery life.