Apparatus and method for charging and testing batteries
First Claim
1. A method for charging a rechargeable battery which comprises the steps of:
- (a) measuring the open circuit voltage of said battery and estimating the number of cells possible for the measured open circuit voltage;
(b) supplying a controllably varying charging current or voltage to the battery for a predetermined period of time and testing said battery for the evolution of gas;
(c) charging said battery automatically at any charge voltage until the battery charge voltage equals the estimated number of cells of the battery multiplied by a predetermined voltage which is characteristic of the battery;
(d) repeating steps (a), (b) and (c) until step (b) indicates the evolution of gas;
(e) determining the current and voltage at which the said battery evolves gas in the increasing current direction ("Igas-up") or in the increasing voltage direction ("Vgas-up"), and the current and voltage at which the battery stops evolving gas in the decreasing current direction ("Igas-down") and in the decreasing voltage direction ("Vgas-down");
(f) determing the true number of cells in the said battery from Vgas-up and/or Vgas-down;
(g) charging the said battery automatically at any charge rate until the battery voltage equals the true number of cells multiplied by a predetermined voltage which is characteristic of the battery;
(h) charging the said battery at a constant voltage equal to voltage in step (g) until the charge current decreases to a predetermined low value;
(i) charging the said battery with a predetermined constant current at any voltage for a predetermined period of time; and
(j) repeating steps (b), (e), and (i) until step (b) indicates the evolution of gas and step (e) indicates that Igas-down reaches a predetermined lower limit which is characteristic of the desired state of charge of the battery.
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Abstract
This invention is directed to a methjod for charging a rechargeable battery. In this method, the open voltage of the battery is measured and the number of cells estimated. The state of charge of the battery is then tested by supplying a controllably varying charging current to the battery and testing for evolution of gas. If no gas is evolved, the battery is charged until the voltage equals the estimated number of cells multiplied by a voltage which is characteristic of the battery. The foregoing steps are repeated alternately until gas evolution occurs. The true number of cells is then determined and the battery is charged at any charge rate until the voltage equals the true number of cells multiplied by a predetermined voltage. The battery is then charged at that voltage until the charge current decreases to a predetermined low value followed by charging at that predetermined current at any voltage for a predetermined period of time.
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Citations
11 Claims
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1. A method for charging a rechargeable battery which comprises the steps of:
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(a) measuring the open circuit voltage of said battery and estimating the number of cells possible for the measured open circuit voltage; (b) supplying a controllably varying charging current or voltage to the battery for a predetermined period of time and testing said battery for the evolution of gas; (c) charging said battery automatically at any charge voltage until the battery charge voltage equals the estimated number of cells of the battery multiplied by a predetermined voltage which is characteristic of the battery; (d) repeating steps (a), (b) and (c) until step (b) indicates the evolution of gas; (e) determining the current and voltage at which the said battery evolves gas in the increasing current direction ("Igas-up") or in the increasing voltage direction ("Vgas-up"), and the current and voltage at which the battery stops evolving gas in the decreasing current direction ("Igas-down") and in the decreasing voltage direction ("Vgas-down"); (f) determing the true number of cells in the said battery from Vgas-up and/or Vgas-down; (g) charging the said battery automatically at any charge rate until the battery voltage equals the true number of cells multiplied by a predetermined voltage which is characteristic of the battery; (h) charging the said battery at a constant voltage equal to voltage in step (g) until the charge current decreases to a predetermined low value; (i) charging the said battery with a predetermined constant current at any voltage for a predetermined period of time; and (j) repeating steps (b), (e), and (i) until step (b) indicates the evolution of gas and step (e) indicates that Igas-down reaches a predetermined lower limit which is characteristic of the desired state of charge of the battery. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. (c) analyzing the data using the differential di/dV vs. I and V, wherein I is the current and V is the voltage, or dZ/dV vs. I or V whereis I is the current, V is the voltage and Z is the impedance;
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(d) determining the gas evolution parameter by the presence of one or more maxima in di/dV or dZ/dV in the increasing current direction and the gas stopping point by the presence of one or more maxima in di/dV or dZ/dV in the decreasing direction of said voltage.
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Specification