DEVICE FOR ESTIMATING AMOUNT OF HEATING OF BATTERY FOR POWER TOOL, AND DEVICE FOR POWER TOOL

A disclosed heat generation amount estimation unit is used for a battery for an electric power tool, and estimates a heat generation amount of the battery that is a power source of the electric power tool. The heat generation amount estimation unit includes a computation device, and is provided in an apparatus for electric power tool. The computation device periodically reads, either during a discharge from the battery or during a charge to the battery, a detected current from a current detection device, which detects a current corresponding to this point in time from among a discharge current and a charge current flowing through the battery, and adds/subtracts a heat generation amount equivalent value in accordance with a value of the read detected current. The computation device outputs the added/subtracted heat generation amount equivalent value as an estimated value representing the heat generation amount of the battery.