Don't ask me why... confused
An Optima battery needs a special charging cycle..
Even though some smart chargers state they can handle AGM batteries..
I have Optima batteries in all (4) of my cars, typically I get 6-8 years, sometimes up to 10 years.
If an Optima battery is low, I bought an Optima charger, and it works great to bring it back up.
1 of my Optimas'(yellow top) I accidently left a small hood light ON and it ran the battery down, hooked up the Optima charger and the battery recovered just fine..

Just my $0.02... wink