This may be too basic but batteries mounted in series add voltage, i.e. 2 ea. 12 volt bats. will give you 24 volts. You would have to mount them in parallel, or use 2 ea. 6 volt bats.
Allen G. Wiesner KR-2S/TD S/N 1118 65 Franklin Street Ansonia, CT 06401 (203) 732-0508 flash...@usadatanet.net