Will a 48V cart run on 38-42 volts?

[rebel1086]

Received 2010 Precedent 48V. Currently individually charging each battery with trickle charger. The charger that came with it would not turn on but from what I've read if the voltage is super low the charger wont turn on. I've charged 3 of the 8v batteries but I've only gotten up to 21V. If the other batteries only get to 6 or 7 volts will the cart even run. I would like to determine if I need new batteries or a new charger. Previous shop wrote in sharpie under the seat that the batteries were changed in September of 2015 so theyre only about 3 and 1/2 years old. I changed the rectifier, relay and fuse on the charger to eliminate those as problems. Not sure where to go next.