Battery charge state determination
First Claim
1. The method of determining the charge state of a battery comprising the steps of:
- measuring the temperature of the battery;
measuring the open circuit voltage of the battery;
subtracting a reference temperature value from the measured battery temperature to form a temperature shift;
multiplying the temperature shift by a temperature shift constant to form a temperature shift voltage;
adding the temperature shift voltage to the open circuit battery voltage to form the compensated battery voltage; and
computing the charge state of the battery from the compensated battery voltage.
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Accused Products
Abstract
Method and apparatus for accurately determining the charge state of a battery is disclosed. The charge state is derived from the battery voltage, which is corrected for errors introduced by temperature and series resistance. Error from series resistance is minimized by either making an open circuit voltage measurement, or by making a plurality of voltage measurements under known load conditions, calculating the series resistance from these measurements, and calculating an equivalent open circuit voltage, compensating for the voltage drop caused by the series resistance of the battery. Errors introduced by temperature induced shifts in battery voltage are corrected by reading the battery temperature and correcting the battery voltage to a reference temperature. The battery voltage corrected for temperature and series resistance effects is used to compute charge state by table look up or algebraically.
297 Citations
6 Claims
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1. The method of determining the charge state of a battery comprising the steps of:
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measuring the temperature of the battery; measuring the open circuit voltage of the battery; subtracting a reference temperature value from the measured battery temperature to form a temperature shift; multiplying the temperature shift by a temperature shift constant to form a temperature shift voltage; adding the temperature shift voltage to the open circuit battery voltage to form the compensated battery voltage; and computing the charge state of the battery from the compensated battery voltage.
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2. The method of determining the charge state of a battery comprising the steps of:
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identifying the battery type; measuring the temperature of the battery; taking a plurality of battery voltage measurements under known load currents; calculating the voltage drop due to the internal battery series resistance of the battery from the voltage measurements; adding the voltage drop due to the internal battery series resistance to the battery voltage to form the equivalent open circuit battery voltage; compensating the equivalent open circuit battery voltage by the battery temperature based on the battery type to form a compensated battery voltage; and computing the charge state of the battery from the compensated battery voltage. - View Dependent Claims (3, 4, 5, 6)
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Specification