But you can use 24 volts from the SYSTEM to charge batteries. I suspected triple A would just laugh if i called them and said, " come jump start my 24 volt truck". So, i put a pair of batteries in the back by the spare tire, wired in series. Then i used 10ga. wire through a double pole switch to the 24v buss bar for the radio power in the back seat. I open the switch when the truck sits, to keep from losing the auxillary batteries to any potential parasitic drains in the system. After i start, i close the switch and the batteries stay charged. If i need to jump start myself, i just drag out a set of homemade 1AWG jumper cables. Someday i'll track down a NATO slave cable end and i won't even have to open the hood.