If you do need a larger charger, check this website.
http://www.bestconverter.com/Check your wiring. If you have #8 wire between converter and battery, it should be fused at 40 or 50 amps, and you can get that large of a converter. If the wire is larger (or easy enough to replace) you can go with #6 wire and a 65 amp converter/charger.
The 220 amp hour golf cart batteries can accept 50 amps at a time (and your RV might be using the additional 15 amps) and quickly charge from a generator. If you normally charge at a RV park, then a 45 amp unit can charge for hours at the 25 - 35 amp rate, and fully charge overnight. Yet if you normally dry camp,and would be using a generator, then the 65 amp converter/charger can save generator run time, gas, and noise!
Fred.