I'm not sure. Perhaps they don't handle high capacity charge -
discharge cycles very well under heavy use.

All I know is that I had a set of AGMs on my Ranger producing 24 Vdc
for my MotoGuide 67 Great White and they were useless after about two
or three long discharge uses - they would take a charge, but last
about a half hour. I didn't even get a month out of them.

The two Interstate HD RV/Marine batteries I have in the boat now are
two years old, take a quick charge and last as long as I need them to
when fishing.

I've been told they've built some different AGMs for trolling
purposes, but I wouldn't ever use them again.


While your experience was indeed real, I suspect it was an exception to,
rather than the norm.