My single, 90Ah Northstar AGM, at ~750 Deep cycles and 51 months of age accepts 65 amps for 19 minutes before reaching absorption voltage, and it alway holds higher voltage under load for the same Ah removed from it after the high amp blast.
I've seen it suck up 105 amps from my alternator.
I think many people are still stuck on the 'trickle charge' is always best mentality, and some others think that a lower voltage just takes longer.
Sometimes I plug in my Meanwell when it is set at 13.6v from floating previously, and do not bother with raising the voltage. My Ammeter reading amps into battery will at some point read +0.0 amps, and my AH counter will still read several AH from full, but it is accepting 0.0x amps. Then when I crank up voltage to 14.7 it is accepting 7 amps, and then takes ~2.5 more hours for amps to taper to 0.45 or less.
So obviously 13.6v will not fully charge my battery at this stage in its life, no matter how long it is applied.
I will hypothesize that with more age/abuse/accumulated cycles, the more pressure is needed, and for longer, and that battery manufacturer specs never account for what the battery requires once it has grown longer in the tooth.
If I had an Automatic smart charger, I would not have been able to discern anything, but manual Pressure control and watching the amps flow is so revealing, that my previous ignorance is embarassing.
