I have a AGM battery and currently use a battery tender. It seems to work, however, you guys recommend that ?
Afternoon TG R1150RT
It really depends on the AMG battery charging voltage requirement & the version of Battery Tender that you have.
Even a Battery Tender to AGM battery mismatch will charge the battery 80%-90% or so & that will work short term but long term using a lower voltage Battery Tender on an AGM that requires a higher voltage & a controlled current charge will ruin the battery, or at least sulfate it enough to significantly lower it's capacity.
The above is even worse in colder weather as the AGM requires higher voltage yet in cold ambients.
If you are going to keep using a non AGM rated Battery charger on an AGM battery then ONLY charge it long enough for the charger to go into maintain mode then disconnect it (ie don't leave it connected long term)