A charging system on a run stand is totally unnecessary. Just run any sort of a generator or alternator as an idler to run the water pump, with no wires attached, and run a battery charger on the test stand battery to keep the voltage constant on the ignition system.

I don't even bother with a radiator or a water pump for a break-in run- - - - -just plumb a garden hose to the water pump inlet and let the warm water run out of the thermostat housing, without a stat installed. Control the engine temp by adjusting the volume of water the hose runs through the engine.
Jerry

Last edited by Rusty Rod; 08/23/2023 3:50 PM. Reason: removed non essential statement
"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!