ESTIMATION APPARATUS, BATTERY, VEHICLE, AND ESTIMATION METHOD

An estimation apparatus for estimating internal resistance of an engine starting battery includes a processor that executes first estimation processing for estimating the internal resistance of the battery by a first estimation method based on a current change and a voltage change of the battery at the time of cranking by an engine starting apparatus, and second estimation processing for estimating the internal resistance of the battery by a second estimation method different from the first estimation method for a period from the cranking by the engine starting apparatus to the next cranking.