Abstract: To prevent reduction in the efficiency of a battery in the wintertime for batteries used on vehicles outdoors, charging runs are automatically initiated in two or three hour intervals which are timed by 10 Hertz (Hz) clock pulses that are applied to a first counter normally used to measure the potential of the battery with the output from a selected terminal of the first counter being applied through a summer-winter switch to a second counter normally used to measure the rate of change of the potential of the battery. When the number of counts have elapsed indicating a two or three hour delay, the output from the second counter initiates a charging run. The summer-winter switch may be manual or temperature-controlled and may include one or more other positions to disconnect the timing circuit or connect a different terminal of the first counter to the second counter to initiate charging runs every two and one-half days during storage of the battery for long periods of time.