Optima Batteries were nto designed to be used with a run of the mill battery charger. They were designed to be jumped by a jumper battery, power pack, or another car.
My optima dealer has told me a regular battery charger for a car will kill a cell or more on the battery and it will not function properly.
'92 300CE - Sold
2004 C240 - C7 Wheels
2015 ML350 - P1, Pano, Ash poplar wood, Sport Dinamica interior, Running Boards Keyless go.