The only time I run a generator with the wires disconnected is when I'm checking for residual voltage. Grounding the field with nothing connected can cause a major voltage spike- - - -30+ volts in a matter of a second or two. Once the battery gets into the circuit after the cutout relay closes, it acts like a shock absorber to dampen out big voltage swings.
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!