People often erroniously refer to agm batteries as gelcells.
An agm is not a battery with gelled electrolyte. An AGMs liquid electrolyte is absorbed within the glass matt.
When an actual gelled elecyrolyte battery is charged at a high rate, volds can form in the gel.
Voltage, is electrical pressure and more pressure means more amperes will flow.
The battery itself decides how much amperage it will accept, at the voltage at the battery terminals, upto the amperage limits of the charging source.
The healthier the battery, and the more depleted it is, the more amperage it can accept, often exceeding the maXimum output amperage of the charging source.
A well depleted healtjy gel battery hooked to a powerful high amperage source can cause void into form in gelled electrolyte.
This does not happen with agms.
Agms if charges at high rates to high voltages can vent, so instead of 99%+ recomnbination of charging gasses, it might be only 85%. High amp recharge an agm battery at too high voltages too often, for too long, and there is the risk of 'drying' it out.
This becomes more likely as the battery ages, its resistamce goes up and it heats more during charging, creating more pressure and more likelyhood of offgassing.
Most cheap agms say to limit charging amps to 30 per
100ah of capacity
Odyssey, northstar and lifeline basically say no amperage limit, just prevent overvoltage.
Lifeine outright states more charge amperage is better. And in deep cycle service, no less than 20 amps per 100 ah of capacity. Odyssey says no less than 40 per 100.
Not sure what northstar says, I've used odyssey guidance for my northstars.
Tppl agms, the best way to restore capacity is a high amp recharge from a well depleted state, and continue to hold absorption voltage until amps taper to less than 0.5 per 100ah of capacity, then float at 13.6v at 77f.
Low and slow recharging a deeply cycled agm will tickle itnto a premature death.
80 t 100% state of charge is no less than 3 hours...ever, and just gets longer and longer the less healthy the battery.
Higher voltage will not significantly reduce 80 to 100% times.
And 14.8v or higher should not be allowed except with low battery temperatures.
Those agms which say no higher than 27 or 30 bor 33 amps per 100 ah of vaoacity dekanintimidator is one such battery, can and do easily accept more.ampergae than this maximum amperage recommendation.
I often double and triple the maximum recommended charge rate of agms, and get exceptionalnlife from them.
I just monitor them for excessive heating when high amp recharging. Only when they are older, and well depleted, and in high ambient temp, do they get over 105f, in my experience.
Not sure the full charge resting voltage of actual gel batteries. My northstars are 13.06v, the dekas agms are 12.78 to 12.84.
Small loads can drag the Northstar to 12.8, but they always rebounded to above 13 once the small loads were removed.
Watch how much amperage a battery acceptsat the voltage reaching the battery terminals.
Voltage alone can be extradorinarily misleading, and voltage does not equal a fuel gauge or am percentage
Voltage isnonlybuseful as to statenof charge whe no loadsmor charging sourcesnhave beennplacednon the batterynfor many manybhours, and atbthatnpointnitnitnuseful for accurate comparison against that same battery at the same temperature. If i were to compare.my dekas agains the northstars by full charge resting voltage. 25% or greater error would be expected.
Get am ammeter.