Over the last 12 years I have gone through 2 Odessey 920 batteries, 1nd 2 Concord 35ACX Batteries. I am looking for a battery tender / charger that will prolong the life of these expensive batteries. Does anyone have a proven unit that is under 200 dollars. The battery tender I was using up until a few years ago was a cheap unit (under 30 dollars) that may be the reason I went through so may batteries? Who has a suggestion for a Concord sealed battery that works by maintaining the batteries life over 3 years.