What's the deal with AGM batteries?

[RobLewis]

I have a 4000W Coleman generator, a MTD lawn tractor, and a John Deere Gator that are all in their 20's in age. When new battery time comes, is there a downside (or an upside) to getting AGM batteries? I've read that standard lead-acid chargers will damage AGM batteries; true? Any tips appreciated. I guess the claim is that AGM batteries last longer; is it worth it?

 

[SHOZ]

The OE Hyundai batteries I had and the new JD mower battery are all sealed vented lead acid but there is no access to add water. Usually there is an internal baffle and any fumes will condensate, also has a pressure relief system. AGMs we made had a 10 psi cap per cell but were big cells..

The Evermax I now have in both cars has vent caps but I personally witnessed the hired help carry one from the back of the store with the vent caps pointing sideways and didn't leak a drop! I was freaking out they were clueless......