The voltage of the system is not a factor..the current is what counts..the ideal charger will keep the voltage to 14.2-14.6 area and the current level will be as high as the batteries will accept..if the batteries will accept 20, or 30 amps and your charger can not deliver, that is your problem..bottom line...get a bigger charger! as you can see, this is why higher amp chargers are the way to go..and why they cost more..I know money is always a concern for all of us, but you will do your batteries a favor by getting the best you are able too.my system is 36v, and my charger is 15 amp per channel..it was not cheap either..HTH..5