The Emergency Services Agency said it received multiple Triple Zero calls about the Keenan Street, Evatt, fire shortly after 1am.

"Crews were able to extinguish the fire quickly and have since determined it accidental," it said in a statement.

"A battery charger had been stored on top of a larger battery which generated heat. The contents of the residential garage were extensively damaged, which included a boat and motorcycle."

The fire brigade sent three pumpers, the Breathing Apparatus Van and a commander.