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OP, you said you use your NOCO for trip preps. I have the NOCO 7200 as well as was thinking of using it while car camping with full hook up to maintain the battery while running lights and fridge. I have a blue sea outlet on the back of the rig. have you done something similar?

Sorry to revive this from last year, but two different schools of thoughts on this. I've seen folks who never AC charge their batteries when under load yet others who do it and have done it for quite a while. NOCO actually makes accessories that allow you to do this so it shouldn't be problematic IMHO.

I plan on tapping into AC/shore power if available if I'm camping at a camp ground for example but I'll probably use it to run my refrigerator directly though I don't think we need to worry about plugging in the AC charger into shore power and charging the battery that way.

I have a 10 Amp Noco and an OBDII connector in case I want to AC charge it with the battery installed.

I agree with some of the views on this thread in terms of best approaches to keep an AGM topped up and happy so that it lasts a long time. IMO the correct order in terms of investing in this should be VB/or an appropriate alt upgrade --> AC charger --> Solar but that's just based on my research and talking to folks here and with others who have gotten many years out of their AGM's. VB's run anywhere from $10 to $75 so are probably the cheapest options out there. Excellent place to start.

I have one question here for those running stock alternators and a VB and cycling their battery often. How long does it typically (i realize that it depends on quite a few variables) take to get a high capacity AGM (G31 or 27 for example) back up from 50% to say 90% SOC with the engine on or the when driving? This with the VB on and getting at least 0.5 V above the stock alt capacity on these 5th gens? Just trying to figure out how many amps the stock alternator will be happy to give to these batteries at that SOC. I'm primarily interested in this because I plan on running a G27 starter battery that would be supplemented by solar and wanted to know how much daily engine run time I'd need to bring the state of charge up from say 60% to 90% in case of cloudy skies and nothing from solar. I currently have a G34 Odyssey but haven't really discharged it to that SOC as I don't currently run a fridge so don't have personal experience of this particular vehicle.

i usually see about 40ish A net (not gross) going into my battery after it's been parked for awhile and the battery SOC is lower. I only monitor amperage on the total battery output so i can't differentiate between load vs charging amperage, but i think my idle load is about 10-20A depending on if the fridge is running so my guess is that the alternator is putting out about 60 A after I'm parked for awhile and the battery SOC is lower.

Thanks for this. So assuming 40A on average with say 35 A on idle being conservative, this should mean that a 90 Ah battery should be able to get through 50% SOC to that 85%+ stage in about 45 minutes or so. Do you think that is a good ballpark to assume in case solar is of no use?

charging gets slower as the battery gets more full, so i'd at least double the estimation

.....

another thought that might be helpful:

before I had my solar panel, my 45min-1hr each way commute was enough to keep the battery recharged from the fridge running while parked from ~6pm to ~8am. after i moved, my 20 min each way commute was not enough to keep the battery charged and after about 4 or 5 days i would hit the low voltage shutoff at the highest setting on my dometic fridge if i didn't maintenance charge.

(i now have 100W solar and also have an onboard charger i use when parked for extended period of time, so haven't hit low voltage shutoff since before solar)

This is an over simplification, but lead batteries have a charge profile where the time to fill is not linear with the available input current.

The ability to accept a bulk charge quickly tapers off and you will end up in an absorption phase with takes a good while to really top off.