We recommend the Victron Orion-Tr Smart 12/12 18amp DC-DC charger. It regulates the charging voltage/current properly for the trailer battery, prevents backflow between the trailer and vehicle, and is compatible with both smart alternators and lithium batteries. If your tow vehicle has a smart alternator, we strongly recommend using a properly configured DC-DC charger between the vehicle and the trailer battery. Smart alternators often reduce charging voltage while driving, which can make direct charging through the standard 7-pin connector unreliable, especially for lithium batteries.

For best performance, we also recommend using 10ga charging wire between the tow vehicle battery and 7-pin plug whenever possible. Because the run of wire is so long, charging performance will always be limited, in practice we’ve seen between 6-8 amps of charging power which is equivalent to 6%-8% of added charger per hour of driving.

We can install the DC/DC charger for you here in the shop for $480, or you can purchase the charger on your own and we can send you the instructions, wiring harness and provide 30min of phone support for $75.