My opinions, use them at your own risk, and research them as you feel the need to before using them until you content you "get it".
AGM batteries are great for quick energy release and ease of charge, but equalizing them like you would a wet cell battery (flooded vs AGM "absorbed glass mat") has been a bad idea the two times I tried it (against my better judgement
). A little research on my end suggest that 14.7 volts is as high as these batteries should ever be charged, and that should only be with enough current/amperage to get the voltage there, but never more that 0.75 amps on a 6 volt - 3 cell, or 1.5 amps on a 12 volt - 6 cell battery regardless. Like someone else said, fully charge your battery, then maybe even float it at 13.5-13.6 volt and <100 milliamps for a couple of days to really saturate the battery, then equalize it. Never start equalize charging any battery until it has had a full charge done, and never do this inside your home or garage, but only outside or in a well ventilated shop with all the safety precautions that make sense.
The charging algorithms for AGM batteries do not exceed 14.7 in my Midtronics GR-8 charging system I don't believe (a 3000.00 charging system), nor do the voltages go as high in my Schumacher algorithms for AGM's as they do for "wet cell" batteries. That said: LISTEN, - BUT!!!!!, WATER FROM THE BATTERY ELECTROLYTE BEGINS TO SUBSTANTIALLY BE BOILED OFF AT ONLY 14.4 VOLTS, so if you go above this often or FOR A LONG PERIOD OF TIME ON AN AGM, or even on a sealed WET lead acid battery - you will eventually dry out one of the cells, and the battery will be no good, and the dry state could allow the battery to create and electrical arc and result in an explosion; I did not experience this on my AGM's, but I did dry out the cells most likely as both AGM's I tried to equalize a few times, lost ~ 2.1 volts o/v across the battery indicating a killed cell, and the battery sides shrunk in as though negative pressure from lost volume in that cell had been created. Bottom line in my opinion, if you must equalize your AGM, don't go above an average of 0.25 amps per battery cell (0.75 and 1.5 for 6v/3cell and 12v/6cell batteries respectively) and don't even do that unless your going to invest in a battery tester (Harbor Freight Tools sells one that is about $75 bucks that does just fine for measuring internal resistance and open voltage across the terminals (o/v). Use the tester to determine when equalizing is actually helping vs. hurting. If equalizing your battery doesn't decrease the internal resistance of the battery, improve it's resting voltage after a charge is completed and the battery rested for a 12-24 hour period, or for sure if equalizing is increasing your internal resistance, then your not doing your battery any favor by equalizing it unless your trying to put it out of it's misery. It's also great to use to track and assess the general condition of your batteries health and state-of-charge. The ohms resistance (< than 3 is excellent battery condition in my experience, 3-4 is very strong, 4-5 is still really good, 5-7 is starting to suggest the needs to be serviced or replaced, and over 7 is for sure a weak battery ready to let you down when you don't want it to. There's a lot of information and knowledge required to safely equalize a battery, so please be careful, do this at your own risk...(my opinions are mine and are "as is..." without any warranty of safety or efficacy). Battery care can be dangerous, so have eye and skin protection on, never do it without being able to get medical help for yourself, or without being able to access fire control/extinguishers. Just be damn careful. Safe boating!!!
My steps in synopsis:
1. Charge my battery completely
2. Float it at 13.5 - 13.6 volts for a couple of days
3. Measure the electrolyte specific gravity (can't do this in an AGM or Sealed wet Lead-Acid)
4. Equalize at less than 1.5 amps total on the 12v/ 6cell battery and 2.5 to 2.65 volts per cell (15 - 16 volts on a 12 volt battery) HERE IS WHERE THE VOLTAGE FOR AN AGM OR SEALED BATTERY IS RELAVANT BECAUSE YOU CAN'T REPLACE THE ELECTROLYTE OR MONITOR THE INDIVIDUAL CELLS
5. Recheck electrolyte specific gravity and quit equalizing when no further evidence of improvement is noted or if battery starts getting hot, or electrolyte becomes colored at all.
6. Determine if battery if good after 24 hours of rest following any charge or equalization.
AGAIN.....AT YOUR OWN RISK! THIS REALLY IS ONLY SAFE TO DO IF YOUR AUTOMATIC CHARGER HAS AN EQUALIZATION MODE (genius, xantrax, and progressive dynamics make automatic chargers that equalize) BECAUSE DOING IT MANUALLY WITH A DC POWER SUPPLY REQUIRES SOME KNOWLEGE TO AVOID INJURY, FIRE, EXPLOSION, OR EVEN DEATH!!! I wouldn't even do them on my boat, and I don't have a big boat...just sayin'. Take them out and do the equalization in a controlled environment!!!! Did I say...AT YOUR OWN RISK YET????