Dual battery charging is made easy with the Ridge Ryder dual battery isolator. The water and dust proof unit is easy to install, even under the bonnet of your 4x4. Once installed correctly, the isolator waits until the main starting battery reaches 13.3V, then allows charge through to the secondary battery as well. If the main starting battery drops below 12.8V, the unit cuts out to make sure your starting battery stays fully charged. Got a flat main battery? In an emergency, you can press the switch on the top of the isolator and use power from your secondary battery to help start the vehicle, or power a winch etc. If you need installation advice or help, there is a toll free number in the instructions so you can talk to one of our experts. This unit may not be suitable for vehicles with a variable voltage alternator, check with the vehicle manufacturer for more information.