I use 2amp (schumaker I believe) unit on my Cummins (two batteries) and they are original to truck (built June 24, 2002!!) . . . and have other units on other cars . . .just monitor your chargers and batteries to ensure everything is ok. If you are going to go away for extend period of time, then unplug the unit for safety sake. . . one other thing for long battery life - if the caps can be taken off (even when it says "maintenance free"), take them off and ensure that you have fluid level topped up to bottom of cap well (you can see the change from flat level to "cupped' meniscus when level hits bottom of well), using distilled water. I truly am amazed at the batteries in my truck, almost 20 years !! Then again, I don't drive it in winter . . . most of the batteries in my cars are well over 10 years now, with no issues - thanks to battery maintainers. Just use smartly and safely . . .