Adding an auxiliary LIFEPO4 battery, charged off the alternator, to a vehicle 1.1

A schematic drawing showing how an Auxiliary 12 volt, 100ah LIFEPO4 battery can be added to an car, boat or truck.​

Included is low temp charging protection via a common electronic thermostat control board. Isolation is provided via a smart isolator. This prevents the LIFEPO4 battery from discharging into the lead acid starting battery and prioritizes the starting battery for charging. This setup is proven to work well.​

Since a smart thermostat is included, it would be easy to add a heating pad to warm the battery in low temps, to allow charging below a 32 degree ambient temperature. All of this can fit into a common 12 volt marine battery box which is widely available for about $15.​