Gem nev batteries being damaged while charging

I have a 2002 GEM Nev E825. I’m on my second set of batteries in a year. I bought the expensive Trojans from NAPA. The first set died in 90 days. They replaced them. The second set is dead now. I can’t get them to take a full charge. They discharge when a load is not connected. What is causing these batteries to go bad during charging? Is something destroying them or is it coincidental hat two sets went bad? Help

Seems it must be the charger.
Unless you let them go dead.

They did get drained, but that shouldn’t destroy the battery.

It can damage them…
Or if not balanced, they can overcharge.
Bad charger Or set to wrong setting.

I thought about sending the charger in to be rebuilt and set for gel batteries. Do you know who can do that for me?