I've got a lot of recent experience with a Shorie LiFePO battery. The one Battery Tender offers is the same chemistry -- and there's likely only one formula making it onto the market. These are very, very different creatures than the lead-acid batteries we know so well.
They do NOT work at all with the tender-style float chargers we all like. The desulfation mode actually DISCHARGES LiFePO batteries. (Don't ask me how I know.) A special lithium-battery charger is NOT required, though many folks are heppy to sell you one for $70+. What you need is a bare-bones, low-amp trickle charger. Harbor Freight sells a 700 m.amp one for $10 or so. I have had GREAT success using one that had been sitting on my shelf for years.
They do NOT need to be connected to a tender. Fully charge then leave it alone. It will hold almost a full charge for months. (Probably years but I can't go that long without riding.)
They put out energy faster as they heat up -- opposite of lead-acid batteries. Output does NOT diminish as charge is consumed. They put out full voltage until suddenly they don't -- then it's just about nothing.
Did you really "mess up" the first one by not charging it? Seems inconsistent with my experience. LiFePOs can be completely discharged and still function perfectly afterwards. (Don't ask me how I know.) They supposedly are good for 3,000 such cycles. I do not intend to test that number.
The Shorai went into my bike in April of 2012. I have been very, very pleased with it despite not fully comprehending the differences I would encounter when switching from lead-acid technology. (Most of the lack-of-comprehension showed up when dealing with a stator failure.) If it lasts half as long as the AGM it replaced (eight mostly trouble-free years) then I will be completely satisfied.
Amazon has a very good price on the
Battery Tender LiFePO.