I find it sadly unamusing that even the battery makers keep contradicting their own information about how each type is best treated or used. Even in Lifeline's little blurb about battery life, I'm guessing they made an "oops" because their #1 scenario for best battery life does not mention equalizing at all--and they're one of the few AGM makes who say to equalize their AGMs. While most everyone else says that is unnecessary or will kill them.
The AGM makers have changed their data & marketing sheet's many times. When they first came out it was double or triple the cycle life of wets (of course this was all "Lab" not real world). Now it is less than or comparable cycle life to wets. They also said discharge to 80% of the capacity now they say discharge to a max or 50%... The real world and realities of the marine market place seem to thin out the BS over time...
AGM's have GREAT benefits IF you can take advantage of them.
I just finished an install with a bank of 4 Odyssey PC 2150's, an Electromaax 140A alternator, serpentine kit, Balmar MC-614 & Balmar Duo Charge feeding a smaller Odyssey start battery. This set up PUMPS the current and the Odyssey's take it. I ran it at 130A + output for over an hour last week and it was still under 195 degrees!!! Based on the bank size he's not taking a "huge" advantage of acceptance but he's certainly ahead of the acceptance he'd have if his banks had been wet so he's about 40Ah ahead per hour of engine run time which is all in all pretty good. Based on the stock Valeo alt on the Volvo MD 2030 he's about 110Ah ahead per hour of engine run time. I tried to talk him into a 160A or 180A alt but he was concerned about the HP loss..
"BTW this is the hidden cost of the wet cells..acceptance rate and" Chef, I would note that the acceptance rate for wet cells is normally given as C/5 (one fifth of the charge capacity) while it is given as C/4 for AGMs. That means wet cells can be charged at 20% of their rated capacity while AGMs can be charged at 25%. A real difference--but not a huge one. And while many folks have reported charing AGMs way faster for years with good results, again, that's just what the folks who make them have to say about it.
Chef's acceptance story of 3 hours vs. 5 hours makes one stop to pause because based on the numbers given it does not make much sense. I am guessing it is a monitor calibration or set up issue? Very often people forget to program the Peukert number and with a 3.3A draw (based on 80Ah per day energy diet) Chef's 600+ Ah bank is considerably larger than 600 Ah so not really drawn as deeply as one would assume.... Both banks were in bulk and could take WAAAAAAY more current than they both had available so neither boat was limited by "acceptance" unless the wet bank was sulfated due to under charging.....
But AGM does have one compelling case, and that's low self-discharge. If the batteries are going to sit without being trickle-charged, i.e. over the winter while the boat is on the hard with power not always available, that's where AGMs win. They can SIT for six months and pretty much come back to 100% afterwards, while a wet lead battery starts to take permanent sulphite damage at 30 days. If you're living on board or boating every week all year round, or have reliable power (dockside or solar) that's not an issue.
A batteries self discharge drastically slows in colder temps as do the chemical reactions that accelerate sulfation. Our batteries, wet, are left on-board all winter. One winter just to experiment I left them uncharged. They lost very little, and are still going strong at year six. AGM's would have lost less but ours did not lose enough in the cold temps of Maine to have any issues, based on very detailed testing. Ours have been stored on-board for over 20 years and topped up only once or twice per winter. In warmer climates self discharge is a big issue but less so for those of us storing on the hard in the cold white North..
I applaude the folks like bt and Maine who have tried to set up battery banks on the bench and get some objective long-term testing done. And I'm astounded that Maine could leave wet calls all winter and get no capaity loss, cold or no cold. I only wish the industry would try as hard to lose the smoke and mirrors.
To be clear I did not lose "no capacity" but I lost less than I would have expected and I lost more than an AGM or GEL in the same situation. Of course coming from a science and chemistry background it makes sense as chemical reactions, like those in a battery, almost go into hibernation when it is cold..
I'm one of those who has to see things for myself so as a result I do loads of experimenting, Bill T. does too.... My prop drag test locked vs. spinning is but one of my favorites...