An apparatus for powering an electric hand-held power tool device by an output voltage includes at least two connectors for connecting the apparatus to at least two batteries. At least two switches, and a command circuit of the switches, are provided. The command circuit is arranged for commanding the powering of the electric hand-held power tool device by using the battery which presents the highest open circuit voltage if the output voltage is higher than the open circuit voltage of each of the other batteries. And, by using the battery which presents the highest open circuit voltage and at least one other battery if the output voltage is lower than the open circuit voltage of the other battery, the battery which presents the highest open circuit voltage and the at least one other battery being connected in parallel.