Abstract: A catalytic device for a battery containing an aqueous electrolyte into which oxygen and hydrogen gases generated as a result of a electrolysis of the aqueous electrolyte pass and are catalytically recombined into water, which returns to the electrolyte: including a catalyst body; a gas-permeable catalyst vessel having the catalyst body arranged therein; a condenser vessel housing the catalyst vessel, the condenser vessel having an opening only at the lower portion thereof; an outer vessel of the catalytic device housing the condenser vessel; and a conduit or passageway for passing a gas from the condenser vessel through a gap between the condenser vessel and the outer vessel.