I used variations of the so called bad boy setup for charging my Ranger. I always charged from a circuit with a ground fault interrupter which in my never so humble opinion is absolutely essential for any charger without an isolation transformer.
I tried various variacs and other transformers. A bad boy works best when the ac supply voltage is about 90 percent of nominal battery pack. My 120-volt pack needed 108 volts ac to the rectifier. A 132-volt pack can charge from 120 volts ac with no transformer. Extra extension cords are a niggardly way to get by without a transformer. A badboy setup needs a constant voltage which I fortunately have. I have a 50-amp variac fed from a 50-amp circuit breaker. The circuit breaker includes a GFI. The charger setup includes a 50-amp dc ammeter and wiring and rectifier adequate for 50 amperes. Unless my set of golf cart batteries was unusually tired, I could turn up the variac to 90 percent of nominal pack voltage immediately. Current would sometimes go as high as 38 amps initially by drop below 30 in a minute or two. The variac wouldn't need adjusting again during the charge. If the pack were severely discharged, the variac needed to be set below 90 percent for a half hour or so. Tom Shay
