Energy supply device

The device (10) has an energy storage unit (12) comprising rechargeable storage cells (14-20) i.e. galvanic cells, and a fuel storage unit (22) i.e. lubricant storage unit, for storing fuel that is different from fuel in the storage cells. The fuel storage unit comprises a fuel valve (24) that closes a fuel storage space (26) of the fuel storage unit in an automatic manner. The fuel valve is provided to automatically open the fuel storage space in a state found in a portable machine tool i.e. chain saw, and/or in a charging device. Independent claims are also included for the following: (1) a charging device (2) a portable machine tool.