Adapter and electric power tool

An adapter includes a converter unit which increases at least one of voltage and current outputted from a battery pack and supply the increased the voltage and/or the current to a load, and a characteristic detection unit which detects at least one of the voltage outputted from the battery pack, the current outputted from the battery pack, a temperature of the battery pack, a voltage inputted to the load, a current inputted to the load and a temperature of the converter unit. The adapter further includes a control unit configured to control the converter unit to increase each of said at least one of the voltage and the current outputted from the battery pack to a corresponding reference value and perform a control operation of suppressing such increase to prevent an occurrence of over-current or over-discharge based on at least one detection result.