I think BFL13's coined term of progressive sulfation is an apt one for the Op to realize.
Without returning to a true 100% every so often, doing 50 to 90's or 50 to 80's day after day results in less and less capacity available, and at some point the batteries are screaming for a true full 100% recharge, yet are just fed the same regimen of 50 to 90 again and just say 'screw you buddy, I'm done" and take a nose dive, and the battery discharger points fingers everywhere but back at themselves.
Reaching that true 100% is difficult, and obviously time consuming, and if on a generator, a big waste of fuel.
I have 130 amp hours, I reduced my overall house capacity from 230A/h, as I only use 30 to 50 A/h a night on average. My 200 watts of solar, which is not going to increase, works much better feeding a single petulant 130 amp hour battery than it did feeding 2 115 AH batteries in parallel.
While I am not impressed with the peculiar recharge requirements of this particular battery, if I only get one year of 365 cycles out of it, I will be ahead of my previous sets of 2 27's in parallel which I never got more than 2 years from. And so far, since I have figured out what this battery requires to reach near 1.275 daily( cycled nightly) by solar alone, I expect more than a year from it, but time will tell.
If solar is to be the primary recharging source, increase the ratio of solar wattage over battery capacity, is my recommendation. I think that many get a large capacity bank and then just enough solar to replenish what they use, and pay no attention to the minimum bulk recommended recharge rates of the battery manufacturer. Perhaps if their outing is not a long one, and they get to go home and plug in for a few weeks then it is not a big deal.
While Solar is not going to be like the flip of a switch grid powered charging source, a higher solar wattage ratio to battery capacity is going to get the batteries up in the 90% range earlier, giving them more time to approach that 100% area for the rest of the day, as well as counteract usage during the day.
The person who sizes their solar array only to replenish their overnight capacity removal, is eventually going to have a starving battery bank. Pull out the Hydrometer or remain ignorant. Lesser amounts of solar can be thought of as possibly negating usage, but not as a proper recharging source, not after a certain amount of cycles.
My current battery wants a 10% rate and my solar can just barely reach this. 200 watts of Solar to 130 amp hours battery. I think the usual 1 watt of solar to 1 amp hour of battery capacity is way too low. The 5 to 13% of capacity one sees listed on AZ wind and sun forums might be too low as well in RV usage, perhaps not on off grid stick and brick.
My previous batteries had a recommended minimum ~18% rate and my solar was not even meeting 50% of this requirement. They used a lot of water, they got low, they performed badly even before they got low, and were replaced well before they should have been, or so was my thinking at time of replacement.
We often see the same recommendations spouted as gospel. There are large differences in requirements between the person who uses their batteries for 2 weeks here and there and the person who cycles each and every day.
We'll always see somebody claim a certain amount of years from a battery bank, but what is important is not years, but the number of cycles that the batteries lasted for. The person who got a respectable amount of cycles from a battery bank was doing something right. The person who left their converter to hold them at 13.6v for 44 weeks a year and brags about longevity....
sound and fury, signifying nothing
