Battery charger having variable-magnitude charging current source
First Claim
1. A battery charger for charging a battery pack formed of at least one battery cell, when the battery pack is positioned for recharging thereat, said battery charger comprising:
- means for measuring a temperature level of the at least one battery cell of the battery pack;
means for applying a battery charging current defined by a current level to the at least one battery cell when the temperature level of the at least one battery cell measured by said means for measuring is less than a first threshold temperature;
means for reducing the current level of the battery charging current applied to the at least one battery cell in amounts of current level reduction corresponding to amounts of temperature level increases when the temperature level of the at least one battery cell exceeds the first threshold temperature but is less than a second threshold temperature; and
means for applying a trickle charging current to the at least one battery cell when the temperature level of the at least one battery cell exceeds the second threshold temperature.
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Accused Products
Abstract
A battery charger for charging a nickel metal hydride battery with a fast charging current. The battery charger is operative to step-down, or constantly reduce, the magnitude of a charging current applied to a nickel metal hydride battery as the temperature level of the battery increases during charging thereof. As the temperature levels of the battery exceeds preset values, the magnitude of the charging current is reduced. When the temperature levels of the battery exceeds a maximum value, application of a fast charging current is terminated, and a trickle charging current is applied to the battery.
88 Citations
21 Claims
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1. A battery charger for charging a battery pack formed of at least one battery cell, when the battery pack is positioned for recharging thereat, said battery charger comprising:
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means for measuring a temperature level of the at least one battery cell of the battery pack; means for applying a battery charging current defined by a current level to the at least one battery cell when the temperature level of the at least one battery cell measured by said means for measuring is less than a first threshold temperature; means for reducing the current level of the battery charging current applied to the at least one battery cell in amounts of current level reduction corresponding to amounts of temperature level increases when the temperature level of the at least one battery cell exceeds the first threshold temperature but is less than a second threshold temperature; and means for applying a trickle charging current to the at least one battery cell when the temperature level of the at least one battery cell exceeds the second threshold temperature. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A battery charger for charging a battery pack formed of at least one battery cell when the battery pack is positioned for recharging thereat, said battery charger comprising:
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a thermistor positioned proximate to the at least one battery cell of the battery pack, said thermistor forming a portion of an electrical circuit and having electrical characteristics which vary responsive to the temperature thereof, said thermistor for measuring a temperature level of the at least one battery cell; a variable charging current source coupled across the at least one battery cell for applying a battery charging current defined by a current level to the at least one battery cell when the temperature level of the at least one battery cell is less than a first threshold temperature; a processor having inputs thereof coupled to receive signals indicative of the electrical characteristics of the thermistor, and, hence, the temperature level of the at least one battery cell positioned in proximity thereto, and outputs thereof coupled to the variable charging current source; and an algorithm embodied in the processor, said algorithm having a portion thereof for associating signals received at the inputs of the processor with a temperature level of the at least one battery cell, and a portion thereof for causing the processor to generate control signals at the output thereof for varying the current level of the battery charging current generated by the variable charging current source whereby the algorithm causes the processor to generate signals to cause the battery charging source to reduce the current level of the battery charging current applied to the at least one battery cell when the temperature level of the at least one battery cell exceeds a first threshold temperature, but is less than a second temperature level, and for applying a charging current of a level corresponding to a trickle charging current when the temperature level of the at least one battery cell exceeds the second threshold temperature. - View Dependent Claims (19, 20)
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21. A method for charging a battery pack comprised of at least one battery cell, said method comprising the steps of:
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means for measuring a temperature level of the at least one battery cell; applying a battery charging current defined by a particular current level to the at least one battery cell when the temperature level of the at least one battery cell measured by said means for measuring is less than a first threshold temperature; reducing the current level of the battery charging current applied to the at least one battery cell when the temperature level of the at least one battery cell exceeds the first threshold temperature but is less than a second threshold temperature; and applying a trickle charging current to the at least one battery cell when the temperature level of the at least one battery cell exceeds the second threshold temperature.
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Specification