Could be the charge controller it set way too high on charge or float to long before going to float.
Read your manual a couple of times on it.
Batteries may be cooked.
I somehow let the desulfation cycle run too long and cooked the batteries.
Every time something new happens or malfunctions it is do we panic time.
I'm one that who thinks I don't need assembly instructions.
If not for the advise o quite a few I would have foundered.
Wasn't quite sure what to do when plug on water heater blew.Now, I'm prepared to to fix the thing and carry lot of spare plugs and threading tool and so on.