Apparatus for estimating state of charge of secondary battery

A computer-readable recording medium that stores a program for computing a state of charge of a secondary battery, wherein by means of the program a computer performs the following steps:

• storing in memory data pertaining to a voltage of the secondary battery and a charge/discharge current;
• reading from the memory the data pertaining to the voltage and the charge/discharge current by means of a processor and computing an open circuit voltage by means of regression analysis;
• computing a total amount of electric discharge by means of the processor;
• comparing the total amount of electric discharge with a predetermined threshold value by means of the processor and correcting correlation information about correlation between the open circuit voltage preliminarily stored in the memory and a state of charge in accordance with a relationship between the total amount of electric discharge and the predetermined threshold value;
• and
• computing a state of charge of the secondary battery from the corrected correlation information and the computed open circuit voltage by means of the processor,
• wherein the memory stores, as the correlation information, correlation information about an initial state where no memory effect is produced and correlation information about a saturated state where the memory effect is saturated;
• and
• the processor makes a correction so as to replace the correlation information about the initial state with the correlation information about the saturated state when the total amount of electric discharge is equal to or greater than the predetermined threshold value, and makes a correction so as to acquire correlation information achieved by mixing at a predetermined ratio the correlation information about the initial state with the correlation information about the saturated state when the total amount of electric discharge is smaller than the predetermined threshold value.

An apparatus for estimating a state of charge of a secondary battery provided in a vehicle, comprising:

• a storage unit that stores correlation information showing correlation between an open circuit voltage and a state of charge;
• a travel distance detection unit that detects a travel distance of the vehicle;
• a correction unit that makes a correction to the correlation information in accordance with a relationship between the travel distance and the predetermined threshold value;
• and
• an estimation unit that estimates a state of charge of the secondary battery by use of the corrected correlation information,
• wherein the storage unit stores, as the correlation information, correlation information about an initial state where no memory effect is produced and correlation information about a saturated state where the memory effect is saturated;
• the correction unit makes a correction so as to replace the correlation information about the initial state with the correlation information about the saturated state when the travel distance is equal to or greater than the predetermined threshold value, and makes a correction so as to acquire correlation information obtained by mixing at a predetermined ratio the correlation information about the initial state with the correlation information about the saturated state when the travel distance is smaller than the predetermined threshold value.