Here's the new battery setup ready to go. I bridged the two small battery wells together with a wooden platform, then mounted the battery box. It's a large deep cycle. I didn't know the system would automatically charge the battery. Is it like a trickle charger?
There are basically a few different types of chargers
Rapid chargers hit the 12 volt battery bank with as much as 20 or more volts to push amps in there like going out of style (Very hard on deep cycle batteries) some can push 100 amps into a 12 volt battery. These are designed to work for like 30 minutes or less for a quick charge on your STARTING batteries. (And if they need that kind of charge good chance they need replacement).
Trickle chargers are just a few amps.. but they never stop (not good long term)
Smart chargers are amazing Most modern RV converters are smart chargers.
These monitor both voltage and current and may even shut off briefly to measure "Static" voltage. They adjust their output from 14.6 to 13.6 (or there about) Depending on the state of charge of the battery. They can easily push 80 amps into the battery bank. or slow down to 8 or even (13.6 volt) Just balance so that in theory NO current flows in the battery.
And that's the kind you want.