I'd say continue this thread. You can edit the original post and thread title to reflect your desired route change to include chargers.
I'd likely follow BFL13's path and have the charger be a portable, especially since you have mentioned the possibility of scumbag thieves making off with your batteries in previous posts.
If you don't require something absolutely automatic, there is the adjustable voltage power supply route. You can set the desired AbsV, put this on a timer so that it does not hold batteries that no longer need Absorption voltages, at ABSV's.
I have a meanwell RSP-500-15 that will provide 40.94 amps into my Northstar AGM and about an amp less into my flooded battery.
They make a RSP-1500-15, which should do ~123 amps, but it is not cheap, but you could set it to 14.x, crank a timer to ~3 hours (depends on depletion level) and have the 3 31's in the 95%+ range.
Come back at your convenience, set it to float voltage and crank timer again, or just bypass timer to let float voltage safely top them off with no time limit.
Meanwell RSP-1500-15rsp-1500-15 data sheetIt needs 17 amps at 115vac, so a 20 amp receptacle, which can pose problems, but can also handle 240v outlets so if you have one of those handy.
Anyway, it is one option.
Also if you leave the batteries in series for 24 or 36 volts, this presents more charger issues.
Mean well Makes -24 and -27 and -48 volt models with wide voltage adjustment ranges too they are in that PDF above. but no 36v options.
Likely the newer 100 amp powermax boondockers that have adjustable voltage can do the same task a smidge slower and for less money. but then there is the one 12v battery at a time factor
Those sealed marine charger units all seem to be low and $low, but I've not researched all their possibilities.
If you get the higher $$ AGMs which state no bulk current limits, then you will likely find that these batteries respond well to huge recharge currents, and a ~95% recharge in 3 hours could certainly come in handy too.
