Benefit of replacing converter/charger with larger one

Higher amps won't do you much good unless you can do them at higher voltage.

6 volt batteries need 15+ volts to fully charge them. The usual Rv converter can't do that. I use a VEC1093DBD which can do the 15v if set to Equalize to do the "finish" portion of the recharge as recommended here:

http://www.wholesalesolar.com/pdf.folder/battery-folder/charging_instruction_2011_2.pdf

You can use your converter for the first stages and then swap over to the 1093 to finish it off, or just use the 1093 for the whole thing.