Lead batteries in electric vehicles tend to produce electrolytic gas which will entrain acid from the cells during its discharge. The loss of acid will reduce the recombinator efficiency and tends to cause corrosion. To prevent this, an acid separation stage is arranged in the gas discharge duct. The acid separation stage consists of a gas washer and a dry filter. Acid separation is enhanced by small plastic elements arranged in the gas discharge chamber of the gas washer and the gas supply chamber of the dry filter. The gas outlet chamber above the washing liquid has a large volume in order to prevent washing liquid from slopping out.