Abstract: A battery charging system for rectangular, 9-volt batteries has inclined holders with mesh contacts engageable with the terminals of an inserted battery. Reflective tape is affixed to one side of the battery, and an optoelectronic assembly presents a sensing signal whenever the battery is received in one orientation in the holder. The sensing signal reinitializes a pulse counter which then counts a predetermined number of timing reference pulses from a pulse generator. Simultaneously, a control means coupled to the sensing signal renders a charging circuit conductive to charge the battery. Once the pulse counter has received a predetermined number of pulses, the charging circuit is interrupted. If the battery is incorrectly inserted, the charging circuits will not charge the battery, and also a reverse polarity alarm audibly indicates the error. Consequently, the charging system is foolproof, simple to use and can simultaneously charge a multitude of batteries without manual intervention.