Battery Tender Plus 1.25 AMP 6V Battery Charger and Maintainer 36V This certification is a requirement This certification is a requirement for any charging device installed in an enclosed marine space and is not found on standard portable chargers charge voltage adjusts automatically based on ambient temperature throughout all charging stages — a second layer of temperature management on top of the manual winter optimization antique tractors Keeping those batteries alive through the off season is one of the primary maintenance challenges in vintage vehicle ownership — and one that a Battery Tender® Plus 6V solves permanently