Battery remaining quantity estimation apparatus

A battery remaining quantity estimation apparatus that estimates a remaining quantity of a secondary battery based on a charging parameter correlated with charging time of the secondary battery and a rate of change of a voltage of the secondary battery relative to the charging parameter, the battery remaining quantity estimation apparatus comprising:

• a determination unit that determines whether a predetermined condition is met, the predetermined condition being that an amount of change in the charging parameter from the start of charging of the secondary battery until when the rate of change of the voltage becomes a maximum value is equal to or less than a predetermined amount of change;
• and
• an estimation unit that, in response to the determination unit determining that the predetermined condition is met, estimates a remaining quantity corresponding to a portion between two minimum values of the rate of change of the voltage during charging of the secondary battery as the remaining quantity of the secondary battery.