Method and apparatus for determining a capacity of a battery
First Claim
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1. A method for accurately estimating a capacity of a battery, comprising:
- determining if a state of charge of the battery corresponding to an initial state is above a state of charge of the battery corresponding to a rest point; and
if so, charging the battery from the initial state to a fully charged state without interrupting the charging process;
if the state of charge of the battery corresponding to the initial state is below the state of charge of the battery corresponding to the rest point, charging the battery from the initial state to the rest point prior to reaching the fully charged state;
interrupting the charging process to allow the battery to relax to a resting voltage;
measuring the resting voltage;
resuming the charging process toward the fully charged state; and
estimating the capacity of the battery based at least on the resting voltage.
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Abstract
Some embodiments of the present invention provide a system that accurately and reliably updates a full charge capacity of a battery. During operation, the system charges the battery from an initial state to a rest point prior to reaching a fully charged state. The system then interrupts the charging process to allow the battery to relax to a resting voltage. Next, the system measures the resting voltage. The system then resumes the charging process toward the fully charged state. The system subsequently estimates the capacity of the battery based on the measured resting voltage and one or more other parameters.
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Citations
43 Claims
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1. A method for accurately estimating a capacity of a battery, comprising:
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determining if a state of charge of the battery corresponding to an initial state is above a state of charge of the battery corresponding to a rest point; and if so, charging the battery from the initial state to a fully charged state without interrupting the charging process; if the state of charge of the battery corresponding to the initial state is below the state of charge of the battery corresponding to the rest point, charging the battery from the initial state to the rest point prior to reaching the fully charged state; interrupting the charging process to allow the battery to relax to a resting voltage; measuring the resting voltage; resuming the charging process toward the fully charged state; and estimating the capacity of the battery based at least on the resting voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A non-transitory computer-readable storage medium storing instructions that when executed by a controller for a battery cause the controller to perform a method for accurately estimating a capacity of the battery, the method comprising:
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determining if a state of charge of the battery corresponding to an initial state is above a state of charge of the battery corresponding to a rest point; and if so, charging the battery from the initial state to a fully charged state without interrupting the charging process; if the state of charge of the battery corresponding to the initial state is below the state of charge of the battery corresponding to the rest point, charging the battery from the initial state to the rest point prior to reaching the fully charged state; interrupting the charging process to allow the battery to relax to a resting voltage; measuring the resting voltage; resuming the charging process toward the fully charged state; and estimating the capacity of the battery based at least on the resting voltage. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22)
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23. A battery with a capacity estimation mechanism, comprising:
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a cell; a voltage sensor configured to measure a voltage for the battery; a current sensor configured to measure a current for the battery; and a controller configured to receive inputs from the voltage sensor and the current sensor, and to generate a capacity estimate; wherein the controller is configured to; determine if a state of charge of the battery corresponding to an initial state is above a state of charge of the battery corresponding to a rest point; and if so, charge the battery from the initial state to a fully charged state without interrupting the charging process; if the state of charge of the battery corresponding to the initial state is below the state of charge of the battery corresponding to the rest point, charge the battery from the initial state to the rest point prior to reaching the fully charged state; interrupt the charging process to allow the battery to relax to a resting voltage; measure the resting voltage; resume the charging process toward the fully charged state; and estimate the capacity of the battery based at least on the resting voltage. - View Dependent Claims (24, 25, 26, 27, 28)
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29. A method for evaluating a state of charge of a battery during a charging process, the method comprising:
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determining if a state of charge of the battery corresponding to an initial state is above a state of charge of the battery corresponding to a rest point; and if so, charging the battery from the initial state to a fully charged state without interrupting the charging process; if the state of charge of the battery corresponding to the initial state is below the state of charge of the battery corresponding to the rest point, charging the battery from the initial state to the rest point prior to reaching the fully charged state; interrupting the charging process to allow the battery to relax to a resting voltage; measuring the resting voltage; and determining a state of charge of the battery at the rest point based at least on the resting voltage.
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30. A method for accurately estimating a capacity of a battery, comprising:
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charging the battery from an initial state to a rest point prior to reaching a fully charged state; interrupting the charging process to allow the battery to relax to a resting voltage; measuring the resting voltage; resuming the charging process toward the fully charged state; and estimating the capacity of the battery based at least on the resting voltage; wherein prior to charging the battery, the method further comprises selecting the rest point based at least on one or more of the following parameters; a time required for the battery to relax at the rest point; an error associated with a coulomb counting between the rest point and the fully charged state; a likelihood of a user discharging the battery below the rest point; and an open-circuit-voltage measurement accuracy required to compute a state of charge associated with the rest point. - View Dependent Claims (31, 32, 33)
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34. A battery with a capacity estimation mechanism, comprising:
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a cell; a voltage sensor configured to measure a voltage for the battery; a current sensor configured to measure a current for the battery; and a controller configured to receive inputs from the voltage sensor and the current sensor, and to generate a capacity estimate; wherein the controller is configured to; charge the battery from an initial state to a rest point prior to reaching a fully charged state; interrupt the charging process to allow the battery to relax to a resting voltage; measure the resting voltage; resume the charging process toward the fully charged state; and estimate the capacity of the battery based at least on the resting voltage; wherein prior to charging the battery, the controller is configured to select the rest point based at least on one or more of the following parameters; a time required for the battery to relax at the rest point; an error associated with a coulomb counting between the rest point and the fully charged state; a likelihood of a user discharging the battery below the rest point; and an open-circuit-voltage measurement accuracy required to compute a state of charge associated with the rest point. - View Dependent Claims (35, 36, 37)
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38. A method for accurately estimating a capacity of a battery, comprising:
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charging the battery from an initial state to a rest point prior to reaching a fully charged state; interrupting the charging process to allow the battery to relax to a resting voltage; measuring the resting voltage; resuming the charging process toward the fully charged state; and estimating the capacity of the battery based at least on the resting voltage; wherein estimating the capacity of the battery based at least on the resting voltage involves; computing a first state of charge of the battery corresponding to the resting voltage; computing a second state of charge of the battery corresponding to the second resting voltage; determining a coulomb count between the rest point and the fully charged state; and determining the capacity of the battery based on the first state of charge, the second state of charge, and the coulomb count. - View Dependent Claims (39, 40)
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41. A battery with a capacity estimation mechanism, comprising:
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a cell; a voltage sensor configured to measure a voltage for the battery; a current sensor configured to measure a current for the battery; and a controller configured to receive inputs from the voltage sensor and the current sensor, and to generate a capacity estimate; wherein the controller is configured to; charge the battery from an initial state to a rest point prior to reaching a fully charged state; interrupt the charging process to allow the battery to relax to a resting voltage; measure the resting voltage; resume the charging process toward the fully charged state; and estimate the capacity of the battery based at least on the resting voltage; wherein while estimating the capacity of the battery based at least on the resting voltage, the controller is configured to; compute a first state of charge of the battery corresponding to the resting voltage; compute a second state of charge of the battery corresponding to the second resting voltage; determine a coulomb count between the rest point and the fully charged state; and determine the capacity of the battery based on the first state of charge, the second state of charge, and the coulomb count. - View Dependent Claims (42, 43)
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Specification