Which 48V OnBoard Charger?

[techie1]

I am changing my 09 EZGO PDS from 36v to 48v currently with 6 x 6v battteries soon to be 8x6v batteries and I am looking for an onboard charger. I have heard Lester is a good product so I was evaluating this one: Lester 26680 HIGH FREQUENCY, 48V/25A onboard charger. Most cart chargers are 15A so I thought this would be nice to be able to charge faster if needed siince this charger output is 25A. I use my cart in the hills for hunting and maintenance. Currently, I cannot hunt 1 AM hunt without batteries being dead. I am going to test the SG on each cell soon to diagnose that problem and buy new batteries if needed.

I really wanted to install dual 12v chargers with 2 10Amp circuits each to charge 2 batteries per 12v circuit. This way, if I have one battery that is bad, it can only corrupt 1 other battery. Some reason this does not seem to work. The chargers dont finish charging in 12 hours. Actually, I have not had them finish charging at all. Can anyone expain why this would not work? Theoretically this should work very well.
Thanks