I have used a couple different models from Battery Minder and have had very good success with batty life.
I had several AGM battys given to me when pulled from a Corp data center as PM / end of "useful" life. I used some and kept spares on Battery Minders for ~10 yrs and some are still in service on my boat and doing fine.
I permanently mounted and wired their selectable 12V 2-4-8A model to maintain my house bank of 8 - 6V AGM GCs. All are multi stage smart units.
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