AGM Batteries - Any downside?

tatest wrote:
Advantages are "maintenance free" in the sense that you don't have to (can't) replace lost water, and the glass matts will absorb evolved gases if you stay within the design parameters during operation.


Disadvantages are cost, for capacity and life ( number of charge and discharge cycles).

For the AGMs I use, in motorcycles stored for the winter (like the RV) and used occasionally (more often than the RV), they don't last as long as wet cell batteries, either deep cycle or starting batteries. This puzzles me because they are supposed to have a longer life, slower self discharge, but my actual experience is that the kill themselves rather quickly with self discharge in storage. A Battery Tender helps, but wet cells do even better on the same "gently maintain a full charge" regime. My AGM experience is a lot like my NiCad experience, they lose capacity if not used "just right" and the way I am using AGMs seems to be abusive.

I don't think I would have this problem with AGMs used as house batteries for a full-timing motorhome, but for a few days a month, or even a couple days a week, use, with seasonal periods of longer storage (2-3 months) the AGMs are not living longer than wet cells, so for me, not worth the price premium if I have a choice. On motorcycle batteries I don't. On RVs, I do, so accepting that replacement will be frequent, I will buy what keeps replacement costs down.

You make some interesting comments.
What are you referring to with by " staying within design parameters"?
Doies your "battery tender" have automatic temperature-sensing, voltage regulation? These are a must have for AGM batteries.
What is ment by "used just right"?