System and method for charging electrochemical cells in series
First Claim
1. A battery charger for charging a plurality of series-connected cells comprising:
- a D.C. source for passing a regulated current between predetermined first and second current levels through said series of cells, said first current level being in excess of said second current level;
voltage-monitoring means for comparing the voltage of each cell with a reference voltage and for generating an output indicating the status of each cell as below or not below said reference voltage;
current-regulating means coupled to receive the output of said voltage-monitoring means and to generate an output to said D.C. source for current regulation in response to cell voltage status, said current-regulating means operating to increase current as long as each cell voltage remains below the reference voltage but only to said first current level and to decrease current when any cell voltage rises to the reference voltage but only to said second current level;
shunt module means electrically coupled to each of said cells, to said current-regulating means and to said voltage-monitoring means for shunting current around any cell having a voltage not below the reference voltage but only when the regulated current has decreased to the second current level; and
control means for selecting a mode of controlling cell voltage by initially activating said current-regulating means and subsequently activating said shunt module means when said regulated current is decreased to said second current level.
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Abstract
A battery charging system capable of equalizing the charge of each individual cell at a selected full charge voltage includes means for regulating charger current to first increase current at a constant rate until a bulk charging level is achieved or until any cell reaches a safe reference voltage. A system controller then begins to decrease the charging rate as long as any cell exceeds the reference voltage until an equalization current level is reached. At this point, the system controller activates a plurality of shunt modules to permit shunting of current around any cell having a voltage exceeding the reference voltage. Leads extending between the battery of cells and shunt modules are time shared to permit alternate shunting of current and voltage monitoring without the voltage drop caused by the shunt current. After each cell has at one time exceeded the reference voltage, the charging current is terminated.
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Citations
12 Claims
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1. A battery charger for charging a plurality of series-connected cells comprising:
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a D.C. source for passing a regulated current between predetermined first and second current levels through said series of cells, said first current level being in excess of said second current level; voltage-monitoring means for comparing the voltage of each cell with a reference voltage and for generating an output indicating the status of each cell as below or not below said reference voltage; current-regulating means coupled to receive the output of said voltage-monitoring means and to generate an output to said D.C. source for current regulation in response to cell voltage status, said current-regulating means operating to increase current as long as each cell voltage remains below the reference voltage but only to said first current level and to decrease current when any cell voltage rises to the reference voltage but only to said second current level; shunt module means electrically coupled to each of said cells, to said current-regulating means and to said voltage-monitoring means for shunting current around any cell having a voltage not below the reference voltage but only when the regulated current has decreased to the second current level; and control means for selecting a mode of controlling cell voltage by initially activating said current-regulating means and subsequently activating said shunt module means when said regulated current is decreased to said second current level. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of charging a plurality of series-connected cells by passing an electric current through the series of cells comprising:
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comparing the voltage across each cell in the series of cells with a reference voltage; increasing current through the series of cells until a first current level is reached or until any cell voltage reaches the reference voltage; decreasing current through the series of cells when any cell voltage reaches the reference voltage until a second current level is reached; and shunting current around each cell having a voltage not below said reference voltage while maintaining said second current level through said series of cells. - View Dependent Claims (8, 9, 10, 11, 12)
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Specification