Abstract: A method for controlling the charging of fast discharge and recharge type propulsion battery components of engine-electric hybrid drive systems for road vehicles, wherein the control objectives are to, minimize discharge of gas through battery cell vents, minimize fuel use, allow employment of a small battery, and provide for long discharge-recharge cycle life, and the control method consists in the steps of,1--providing so that, if not earlier terminated as a result of operator termination of braking, or a drop in vehicle speed, termination of regenerative braking will be initiated at a point in time determined by a control system generated indication of state of charge just prior to initiation of braking, and the subsequent history of cell current,2--providing so that, following a partial battery discharge, when and as motor speed allows, supplementary engine implemented battery charging will take place prior to the next advent of regenerative braking, with charge termination made responsive to attainment o