Re: Golf cart charger can't recharge batteries
If the batteries are so low that they will not induce the charger to turn on, you can still charge them.
Disconnect all the batteries.
One at a time use a pair of jumper cables jump one battery in parallel with a good battery, like out of your truck. Now connect a battery charger to this pair, the good battery will induce the charger to turn on, charging both batteries. once the cart battery has charger up to 10.5 or more you can remove the jumper cables and continue charging the cart battery, or move on to the next cart battery and repeat the process.
Once all cart batteries are charged up to 10.5 volts or more, reconnect all the batteries correctly and plug in the cart charger.
It may be preferable to charge each battery separately to a higher voltage, i.e., the minimum voltage listed in the manual where you were supposed to recharge batteries.