Battery remaining capacity measuring device

A battery remaining capacity measuring device, comprising:

• voltage detecting means for detecting values of voltage at a battery terminal connected to a load;
• current detecting means for detecting values of current flowing through the load;
• voltage-current changing tendency calculation means for reading values of voltage detected by said voltage detecting means and values of current detected by said current detecting means, for storing the values of voltage and current as plural voltage data and corresponding plural current data, respectively, and for outputting plural voltage data and the corresponding plural current data;
• determination means for calculating a correlation coefficient between the plural voltage data and the corresponding plural current data, for determining that variation of the load is equal to or less than a predetermined amount when the correlation coefficient exhibits a negative correlation and is equal to or greater than a first reference negative correlation coefficient, and for determining that variation of the load is greater than the predetermined amount when the correlation coefficient is equal to or less than a second reference negative correlation coefficient which is less than the first reference negative correlation coefficient;
• voltage-current approximating linear calculation means for receiving the plural voltage data and the corresponding plural current data and determining a voltage-current approximating linear function from the plural voltage data and corresponding plural current data;
• and
• battery remaining capacity calculation means for determining a remaining capacity of the battery by directly receiving values of voltage detected by said voltage detecting means and values of current detected by said current detecting means when the variation of the load is equal to or less than the predetermined amount, and determining the remaining capacity based on the voltage-current approximating linear function from the plural voltage data and the corresponding plural current data.