The WeatherTech Battery Charger constantly monitors your battery’s power levels and will turn on or off to maintain a freshly charged battery. If the battery is low, the compact unit will recharge it at an optimal rate, varying both current and voltage automatically. When the battery is fully charged, this charger will change over to a maintenance mode to keep your battery in top condition--for longer battery life. A built in surge protector helps protect your vehicle’s electronics. Clip onto battery terminals or attach connectors permanently to battery and unplug when not in use. Works for all 12V lead-acid automotive-type batteries. Three year limited manufacturer warranty.