 Since most of the traction motors were removed from redundant stock for fitting into the vehicles, Acton Works have had to convert them from 630 V operation to work on 320 V. The lead-acid batteries are usually recharged inside a depot, although the 1985 batch of locomotives could recharge their batteries from the power rails while moving.All battery locomotives are fitted with tripcocks which are operated by trackside equipment if the train passes a signal at danger.Eighteen (L15–L21 and L44–L54) are also fitted with Central line Automatic Train Protection (ATP).