Some of the cold-country trucks ran a series-parallel system. They put four 6V batteries in series to put 24 volts to the starter, then reconnected them to two 12V banks for charging and lighting purposes. Freightliner was one of the last holdouts using positive ground electrical systems. We had to be very careful when doing a boost start on rigs from that vintage.

Military trucks ran a 24V system, which made them somewhat compatible with the 28 Volt DC aircraft systems.
Jerry


"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!