AGM battery question

[Valiente]

I would agree. Leave that sleeping dog lying unless you are prepared to buy a proper charger at the same time as AGMs. On a mooring you can buy a cheap and flexible solar "mat"-style panel and you can provide a trickle charge for your existing batteries...after you do all the usual stuff like sample the electrolyte with a hydrometer, clean off the contacts, seal the cables, and so on.

Lead-acid batteries in a non-abusive situation should last six-seven years. Baby 'em and keep them charged (but not overcharged) and you can get longer than that. AGMs seem more tolerant of being "off charge" and can be drawn down farther without damage, but just like lead-acids, the key is getting a "shallow draw on a deep discharge" for maximum cycles of use.

[camaraderie]

"the key is getting a "shallow draw on a deep discharge" for maximum cycles of use."

Actually the optimum point of discharge for AGM's is 50-60% generally Val.
This will give you the most AMPHOURS over the life of the battery and cost per amp hour delivered is the best measure of what optimum discharge is.
Yes...you will get more cycles at 30% discharge than at 60% discharge...but NOT double the cycles which is what you would need for the cost to be equivalent.

[Valiente]

Thanks for the clarification, Cam. The rule of thumb for lead-acid seems to be 80% or so, but that indicates that the "sweet spot" for lowest-cost per amp over the lifetime of the battery is different for AGMs.

It's moot, anyway, as I just got off the phone with a guy who's selling me four 135W Kyocera panels, the new FM-60 Outback MPPT, a Pentametric monitot and various DIN breakers, a DC box, junctions, shunts and cables. My credit card's looking pretty worked over, but the whole point is to make so many amps, and to STORE so many amps, that I can experience cloudy, windless conditions for several days without having to motor around in circles just to get a charge on.

After I get all this in place, some sort of AGM house bank will be at the far end, but I still have to compare and contrast.