Electric storage device management system, electric storage device pack, and method of estimating state of charge

A method of estimating a state of charge (SOC) of an electric storage device having a correlation between an open circuit voltage (OCV) relative to a state of charge (SOC), which includes a slight change region and a sharp change region, the slight change region being a region in which a variation in OCV relative to the SOC is equal to or smaller than a reference value, the sharp change region being a region in which the variation is larger than the reference value, the method comprising:

• defining an OCV of the electric storage device based on a voltage detected by a voltage sensor;
• determining whether the defined OCV is within the sharp change region;
• determining an SOC corresponding to the defined OCV based on information stored in a memory if the defined OCV is within the sharp change region;
• determining the determined SOC corresponding to the defined OCV as an estimated SOC;
• and
• prohibiting the determining of the SOC corresponding to the defined OCV as an estimated SOC if the defined OCV is out of the sharp change region.

An electric storage device management system, comprising:

• a voltage sensor configured to detect a voltage across an electric storage device having a correlation between an open circuit voltage (OCV) and a state of charge (SOC), the correlation including a slight change region and a sharp change region, the slight change region being a region in which a variation in OCV relative to the SOC is equal to or smaller than a reference value, the sharp change region being a region in which the variation is larger than the reference value;
• a memory storing at least information on correlation between OCV and SOC in the sharp change region;
• and
• a controller which executes:
• defining an OCV of the electric storage device based on a voltage detected by the voltage sensor;
• determining whether the defined OCV is within the sharp change region;
• if the defined OCV is within the sharp change region, then performing an SOC adjustment which includes determining an SOC corresponding to the defined OCV based on the information stored in the memory, and determining the determined SOC corresponding to the defined OCV as an estimated SOC;
• and
• if the defined OCV is out of the sharp change region, then not performing the SOC adjustment.