It might be worthwhile to mention that those tractors had exactly ONE item that the battery powered- - - -the starter. Ignition was provided by a magneto that generated its own coil primary current, and a specially-wound three brush generator engineered to provide 9.5 volts kept the battery charged. There were no lights, motors, electrically powered gauges, or other electrical devices to be damaged by over-voltage.
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!