Charging rate estimating method, charging rate estimating unit and battery system
First Claim
1. A method for calculating charged rate of a secondary battery which is adapted to supply electric power to a load, comprising the steps of:
- providing a time function for the open circuit voltage of the secondary battery as a function of time with its coefficients undetermined;
measuring voltage samples of the open circuit voltage of the secondary battery at a plurality of different time points within a predetermined period of time after termination of charge or discharge to obtain plural measured voltage samples along time axis;
using the plural measured voltage samples to determine the coefficients of the time function to thereby determine the time function;
calculating a convergent value of the open circuit voltage of the secondary battery based on the determined time function; and
calculating the charged rate based on the convergent value of the open circuit voltage;
wherein the step of providing the time function comprises providing a combination of at least two exponential decay functions in which the combination of N exponential decay functions, hereinafter referred to as multi-exponential decay function, where N is an integer of at least two is given by
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Abstract
The method for calculating charged rate of a secondary battery is intended to calculate charged rate of a secondary battery which supplies electric power to loads, and comprises the step to measure voltage of the secondary battery more than once in a predetermined period of time after termination of charge or discharge, the step to determine the coefficients of a quadric or more exponential damping function which approximates the time characteristic of the open circuit voltage of the secondary battery by recursive calculation with the plural measured voltage values, and the step to calculate a convergent value of the open circuit voltage of the secondary battery from at least the exponential damping function with the coefficients determined above.
Therefore, precise charged rate of the secondary battery can be calculated from the precise convergent value of the open circuit voltage.
19 Citations
16 Claims
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1. A method for calculating charged rate of a secondary battery which is adapted to supply electric power to a load, comprising the steps of:
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providing a time function for the open circuit voltage of the secondary battery as a function of time with its coefficients undetermined; measuring voltage samples of the open circuit voltage of the secondary battery at a plurality of different time points within a predetermined period of time after termination of charge or discharge to obtain plural measured voltage samples along time axis; using the plural measured voltage samples to determine the coefficients of the time function to thereby determine the time function; calculating a convergent value of the open circuit voltage of the secondary battery based on the determined time function; and calculating the charged rate based on the convergent value of the open circuit voltage; wherein the step of providing the time function comprises providing a combination of at least two exponential decay functions in which the combination of N exponential decay functions, hereinafter referred to as multi-exponential decay function, where N is an integer of at least two is given by - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An apparatus of calculating charged rate of a secondary battery which is adapted to supply a load with electrical power, comprising:
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a voltage sensor to measure voltage samples indicative of an open circuit voltage of the secondary battery at a plurality of different time points within a predetermined period of time after termination of charging or discharging; a control unit to receive the measured voltage samples from the voltage sensor to calculate the charged rate; wherein the control unit comprises; a providing means for providing a combination of at least two exponential decay functions in which the combination of N exponential decay functions, hereinafter referred to as multi-exponential decay function, where N is an integer of at least two is given by - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16)
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Specification