The standard FZ10 battery is the DMW-BM7. It is a 7.2 volt/680 mAh Li-ion battery. The battery can be charged in the external charger when removed from the camera. Most digital camera users suggest that a second `back-up' battery be purchased, much in the same way as a film camera user would carry an extra roll of film.
Unfortunately, some poorly made `fake' batteries for the FZ1/2/10 are available (note that the preceding link may not be permanent).
General information about Li-ion batteries