As long as the charger has an AGM setting you should be fine. However a few people have found some chargers to have the setting, but charge at an improper voltage i.e. 15.5-16v where it should never be higher then 15v max. Ideal is 2.4v per cell.
A battery tender is fine for one battery. But it really isn't a good charger. It only puts out a few amps which takes forever to fully charge multile batteries. You are better off buying a charger that has a float setting.
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