These UPG batteries are not very impressive in my opinion.
Besides being sealed, the biggest advantage of AGM is the ability to accept high recharge currents, yet these UPG batteries always list a maximum initial current of 30% or less of battery capacity, and their internal resistance is 2x that of higher quality AGM.
They do not have the very low self discharge rates, and are barely any better than flooded batteries in this regard.
All AGMs really dislike partial state of charge cycling and walk down in apparent capacity each cycle where they do not get back to a true 100%. The better AGMS can be returned to their original capacity before too much of a beating occurs, with an extended absorption charge cycle, but these lesser AGMS seem to have to kiss that capacity goodbye.
Initial price is always a factor, but does not mean the battery is a good value.
Really with AGMs, to keep them somewhat happy in regular deep cycle usage, they need well more than a 2 to one Solar wattage to AH ratio. Otherwise one needs to be able to plug in and feed them from their most depleted state at near that 30% charge rate every so many cycles with about 15 being the maximum before the lead sulfate hardens to the point where it cannot ever be redissolved into the electrolyte.
When the AGMs do not get this, then recharging to apparent full, Which means holding absorption voltage until the amperage tapers to 0.5% of capacity, takes longer and longer. And if they do not get this longer and longer, the capacity shrinks faster and faster.
Far too often, the price and limited gassing potential of AGMS equate them in the minds of the buyers, with super battery status, but reality is, in daily deep cycling, they need higher amp recharges and recharges to full more often than their flooded counterparts, or they lose capacity at a faster rate.
When the average user notices this capacity loss, the battery capacity is already likely in steep decline, and accelerating, with reversal basically impossible, and even a levelling off of capacity decline from that point requires more charging sources. Charging sources which if present from cycle one, would have prevented the premature capacity loss.
So if getting an Expensive AGM, even a bargain AGM, the charging sources should be larger. More Solar, fatter cable to alternator and a plug in charger that approaches the 30% charge rate for those times one can plug into the grid to recharge, or fire up the generator.
These things all cost more upfront, but will have the system be much more reliable for much longer, and will pay for itself in less stress to owner and le$$ battery replacements.
The UPG 8d battery in this thread might benefit greatly from an extended absorption charge. NExt time it is depleted, if one can apply 75 amps until 14.9v is reached, and then hold 14.9v until amps taper to ~ 2.5 amps, it is likely the battery capacity will be restored some percentage. It could take 2 hours before 75 amps gets this battery to 14.9v, and another 10 hours before amps taper to ~2.5 amps. It could take 20 hours. If the battery were new, it would take 3.5 to 4 hours.
This 75 amps applied regular from the most depleted state, every 10 to 15 deep cycles would very much slow the capacity loss of the battery, likely doubling the total cycles the battery is able to deliver before capacity loss becomes apparent to average owner.
The High amp recharge also reduces the time it takes on the next recharge cycle for amps to taper to X amount at 14.X volts. Basically it will take less time to fully recharge the battery, and a fully recharged battery is a happy battery that can deliver its capacity for much longer and many more total cycles.
So what is acceptable to the owner is highly variable. How far they are willing to go to get the most cycles per $$ is also variable, but some minimums should be met.
Hail mary attempts at restoring capacity, well the equipment required for them, if regularly applied from cycle one, would largely prevent the issue from occurring in the first place.
Everything is a trade off and a compromise.
