An electrical appliance 1 such as a hand power tool is connected to a power supply unit 2 also known as a battery/power pack. The electric appliance is protected against overheating without necessitating abrupt stoppage of the operation of the electrical appliance. The invention includes determining a temperature or a variable which depends on the temperature of an element selected from the group consisting of a current supply unit connected with the electrical device, one or several components of the electrical device, and both, and when the determined temperature or a variable which depends on it exceeds a predetermined threshold, reducing power taken from the electrical device until the temperature or a variable which depends on it falls below the threshold or a lower threshold. |