Patent ID: 8390257

Claim:
A battery capacity controller comprising: a battery capacity estimating part that estimates a battery capacity of a battery in which an internal resistance is increased in accordance with a decrease of the battery capacity in the vicinity of a threshold lower limit battery capacity; and a battery capacity correcting part calculates a present internal resistance value and an internal resistance value of the battery which is at the time of the lower limit battery capacity, calculates an internal resistance difference between the present internal resistance value and the internal resistance value of the battery which is at the time of the lower limit battery capacity, and compares the calculated internal resistance difference with a threshold value, wherein the battery capacity correcting part changes, during the discharge of the battery, the estimated battery capacity to a proper value which is lower than the estimated battery capacity, when an internal resistance difference between the present internal resistance value of the battery and the internal resistance value of the battery which is at the time of the lower limit battery capacity is less than or equal to the threshold value.