It would be simpler to acquire a 6 volt trickle charger and plug it in periodically. A fully-charged 6 volt battery will run the vehicle for several hours, even if the charging system is totally inoperative. The 3-brush generator with the cutout relay mounted on top of the generator is really intended to be a maintenance-type system to maintain the battery's state of charge, not actually recharge a low one. Back then, battery charging was a routine maintenance procedure. Some battery manufacturers set up neighborhood charging stations so car owners could have their batteries recharged periodically.
If you do use a trickle charger, keep the amperage down to a range of 2 to 5 amps, and monitor the liquid level and specific gravity. A fully-charged battery's electrolyte (acid) should be somewhere between 1.250 and 1.300 specific gravity. S.G. below 1.250 indicates the battery needs recharging.
Jerry
