BFL13 wrote:
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.
You know... none of that effort and concern would be necessary if you had a 230+A bank of LFPs mounted inside the coach.
{ =^ )
Yeah, it occurred to me after I posted... that you may not have an onboard generator in the Class C. For me... hauling out the generator means pushing a button. Depending on the neighbor sitch, I have no issue running it every morning and evening for a little while; at least enough to warm it up and clear the moisture out of the exhaust pipe. It also means we can run the microwave if we want... without running the inverter. The girls don't seem to need the hair dryer for basic camping, fortunately.
So I haven't worked my 12v hybrids hard yet. And I wonder if I ever will. I had come to terms with the 3 - 12s until I realized the actual measurements of the "Dekas" were a hair under their specs... which meant they would just fit in the tray. So having that much stored energy is more for peace of mind, perhaps.
The Beast has no problem getting 3-12s well into the 16s. It's an unregulated 19A or so, IIRC. So it's really the battery that is pushing back on it... bubbling like Hell all the way. So I'm careful to limit the time. And like you, I have my own general sense of how much the bank needs based on the usage I'm working to recover it from. And after some rest, the SG is there to verify my general senses.
FWIW, 2 of the 3 12s are brand new last year... with minimal dry camping. The 3rd tests out as nearly new. Funny thing is... when I tested them before putting the rig to bed last year, at 75F, they were all around the 1.300 range. So it's actually they who might be lesser suited to floating. I like the 6s for a solar-only application because they take less effort to top. But the 12s would be fine. Something better than nothing.
Also... my notes say they're actually 29s. So maybe 100Ah instead of 95. I feel about 5% better.
The rig came with 2 expensive AGM starting batteries. Pretty sure they're X2 Power 31s. Sadly, I don't believe they were well cared for. I'm keeping a sharp eye on them. I was always figuring I might upgrade the house tray and rotate the 2 newer 29s down to the chassis tray. In good shape, I would imagine they should be able to crank over a C7 Cat. And it might be nice to have hybrids running the slides and such.
