BFL13 wrote:
"...and I installed a new set. It seems to be time to replace them again as they won't stay charged above about 12.1 volts"
An amazing statement! If they took a long time to get that bad, and you kept using them till now, then it would seem you might only need one 12v battery to get the job done. Why buy four new 6s if you only actually need one 12v batt?
This is all very peculiar!
Please explain. It would seem you are saying that long battery life means he has more battery capacity than he needs. Or perhaps you meant that he survived on weak batteries for a while, and that this means he has more battery than needed. Neither makes much sense.