You get an extra 20% AH the first cycle by starting from full before doing 50-80s so we can do two days before hauling out the gen in that scenario.
Have to go down to 50% to get into the zone for faster recharging, less gen time per AH. Only down to 75% first morning. No issue going down to 40% a few times a year with 6s.
Doing Es, did an experiment where I compared the B&D with an adjustable voltage charger. B&D is set to the 4 amp level and does E at 15.7v. Brings battery from 14.8 to 15.7 constant 4.1 amps and after a while amps taper till it says FUL.
The adjustable voltage 55 amp charger set to 15.7 and let loose kicked in at around 4 amps and did the same as the B&D for timing. So the acceptance rate is running things. Note Mex warning that 15.7 is not 16 when trying to charge those 27s, but the 15.7 does get the 6s up ok, even if it takes two doses. Trojan wants 16.2v for its wet batts. (The PowerMax adj voltage can do that-- range is 13-16.5v)
The engineers note from way back on SG says that high SG batts (near 1.300) don't like to be floated long term, and they use lower SG batts for UPS jobs for that reason. Xantrex even had the float stage optional on their three stager if you wanted to not float your batts after they got full.
So that is another good reason to use the 27s on float for that job instead of the 6s. Also they are not new, but will hardly ever be used so can sit there and you get more use out of them.
I would do better with a higher amp charger but my 2200 (1700 really) gen is the biggest that will fit in the C. No built in gen. Sold the Honda 3000 and 100 amp charger had with the 5er, too big for the C. Still get the job done though as described for a winter four nighter.
