I am not sure that another charger
would do you any good. I had an 800 amphour bank that was supported by a 2000 watt Freedom inverter/charger which has a DC charging
capacity of 100 amps.
With the batteries 1/4 discharged I would start the genset to supply power to the charger
. It would charge at 100 amps for 10 minutes, 80 for 15-30 minutes and then drop to 50 or so for the next hour.
Unfortunately the charging algorithms built in to these devices are conservative to avoid damaging the batteries.