What I learned from my little charger adventure with Guest last summer, is that 20 amps is required just to suitably charge a bank of your size. To "over charge" or equalize them, I think 40 or 50 amps would be required.

Talking with the Guest techs about why their unit imploded we deduced that my bank requires 50 amps of charge, just to be suitably maintained. (my house bank is 480 a/h.)

The difference being, if your unit continues to punch in at 20 amps, even after full charge is achieved. Most charges will taper off to maintenance amperage as full charge is approached.