| 摘要 |
A detection value inputting circuit samples a voltage across a battery connected to a load and the current flowing through the load. A correlation decision section obtains a voltage-to-current correlation coefficient between the plurality of voltage data and the plurality of current data. A nonvolatile memory stores as capacity data the inclination and intercept of a voltage-to-current approximate straight line and the battery remaining capacity attained on the basis of the approximate straight line. A data employing range determining section reads out the capacity data from the nonvolatile memory when the correlation coefficient exceeds a given value, determines a data employing range on the basis of the capacity data and further deletes the voltage data and the corresponding current data which do not exist within the data employing range. An approximate straight line calculating section calculates a voltage-to-current approximate straight line on the basis of the plurality of voltage data and current data left after the deletion of the data not existing within the data employing range. A battery remaining capacity calculating section substitutes a predetermined reference current into the approximate straight line to obtain a voltage corresponding thereto and obtains a battery remaining capacity corresponding to this voltage. The data employing range determining section stores the data on the inclination and intercept of the approximate straight line and the data on the corresponding battery remaining capacity as a set in the nonvolatile memory.
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