I have a 1990s Schumacher 6/12 (Schumacher, iconic drag racer team). My charger has been thrown around and dented. Still works like a champ. Use the closed cell/maintenance free mode, as optima is. Just use it to charge once a yr, once it's charged I disconnect it (it's charged), gen picks it up on driving season. I do have one of my batteries laying horizontal for yrs. Great battery the Optima is.
I should also thank Bubba,skip, and the countless others with ever start.
Interstate batterys have 2 different trickle chargers designed for Optima. one is a small ones that comes in 6 or 12v. the other is 12 v only that i use on my RV....DIGITAL 400
12V PERFORMANCE CHARGER and BATTERY MAINTAINER