This is a waterproof onboard Charger/Maintainer that can charge/maintain up to 2 batteries at once! Just plug your extension cord into this unit after your fishing trip is over and leave it alone, if you want to fish again tomorrow or 6 months from now, this charger will ensure your batteries are ready when you are. 12-24 Volt - 6 amps per bank - 12 amps total - 3"Hx6.5"Wx7.25L - 5LBS.