Land Rover Defender 110 County - Our Dual Battery Setup with a 20A Battery to Battery Charger.

This is my experience of putting two batteries in a Defender and some ideas. I'm not an auto electrician and you should take professional advice if you don't feel competent to undertake this sort of work - there are many potential hazards if you get it wrong - including the risk of serious fire / burns etc. We have deliberately fused the output from our second battery at 20A and wired it with cable rated at 40A. Our use for the second battery will be low current draw for long periods (fridge and Eberspacher heater). We will be monitoring carefully the working temperature of the Battery to Battery charger, particularly when its providing its rated 20A to the second battery when the second battery is low after prolonged use. If necessary we will add additional ventilation, possibly via a thermostat controlled fan in the battery box with outside air ducted in.