Method and apparatus for charging batteries
First Claim
1. A method of controllably charging a battery over a charging period, comprising the steps of:
- connecting a charging voltage to the battery;
applying a plurality of separate and distinct voltage steps in the charging voltage to the battery, the plurality of voltage steps being distributed over the charging period and each having a step magnitude significantly smaller than the charging voltage applied to the battery, for each of the plurality of voltage steps;
detecting current changes induced by said each voltage step;
calculating a ratio from the detected current changes; and
varying the charging voltage according to the ratio.
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Abstract
A method and apparatus for efficiently charging lead-acid batteries applies small voltage steps to probe the charging efficiency of a battery being charged. The application of a voltage step causes the current to change from a base current to a surge current immediately after the voltage step, and to decay asymptotically to a plateau current after the surge current. A current ratio, defined as the difference between the plateau current and the base current divided by the difference between the surge current and the base current, is used as an indicator of the charging efficiency. The output voltage of the power supply charging the battery is then adjusted according to the measured current ratio. A current-voltage slope, defined as the difference between the plateau current and the base current divided by the magnitude of the voltage step, may also be used as an indicator of the charging efficiency for controlling the charging process. Alternatively, in a current-controlled charging process, small current steps are used to probe the charging efficiency. For a current step, the induced voltage changes are measured, and a transient-plateau voltage ratio is calculated. The charging current is then adjusted according to the calculated voltage ratio.
296 Citations
33 Claims
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1. A method of controllably charging a battery over a charging period, comprising the steps of:
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connecting a charging voltage to the battery; applying a plurality of separate and distinct voltage steps in the charging voltage to the battery, the plurality of voltage steps being distributed over the charging period and each having a step magnitude significantly smaller than the charging voltage applied to the battery, for each of the plurality of voltage steps; detecting current changes induced by said each voltage step; calculating a ratio from the detected current changes; and varying the charging voltage according to the ratio. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An apparatus for charging a battery comprising:
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a variable DC power supply for providing adjustable charging voltage and charging current to the battery; a voltage controller for controlling the charging voltage of the variable DC power supply over a charging period and for applying a plurality of separate and distinct voltage steps distributed over the charging period to the battery for probing charging efficiency, each of the voltage steps having a step magnitude significantly smaller than the charging voltage applied to the battery; a current detector for detecting current changes in response to said each voltage step; and an analyzer for determining a ratio from the detected current changes for said each voltage step, the voltage controller being coupled to the analyzer for varying the charging voltage according to the ratio for said each voltage step. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. A method of charging a battery, comprising the steps of:
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connecting a charging current to the battery; applying a current step in the charging current to the battery; detecting voltage changes in response to the current step; calculating a ratio from the detected voltage changes; varying the charging current according to the ratio. - View Dependent Claims (25, 26, 27, 28, 29, 30)
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31. An apparatus for charging a battery comprising:
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a variable DC power supply for providing adjustable charging current to the battery; a current controller coupled to the variable DC power supply for controlling the charging current and for applying a current step to the battery to probe charging efficiency; a voltage detector for detecting voltage changes in response to the current step; and an analyzer for determining a ratio from the detected voltage changes, the current controller being coupled to the analyzer for varying the charging current according to the ratio. - View Dependent Claims (32, 33)
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Specification