What Type of Charger is Needed to Charge a Lithium Battery on a Trailer

Updated 08/07/2025 | Published 07/09/2025

Question:

Hi, I need the for dummies explanation on something. Im looking to upgrade the battery on my travel trailer from lead acid to lithium. i want my truck 170 amp alternator to give a basic charge to the trailer battery just to recover it powering a 12v fridge while in transit. Because of the lithium Im looking to get a dc-dc charger for the travel trailer to properly charge the trailer battery and to protect the truck battery/alternator. So my questions are 1 do i need an isolated or non isolated dc-dc charger? 2 is it necessary to run a separate 4 or 6awg wire from the alternator/battery to an anderson plug in the back of the truck? wouldnt this still have power coming through the 7 pin connector thats unregulated? 3 if using an isolateed dc-dc charger, how would it connect back to the negative terminal on the tow vehicle battery? Im not trying to use the tow vehicle gas silverado HD as a generator, just trying to keep enough charge to prevent the battery dying from the charge is loses powering the 12v fridge and other minor accessories. and for the dc-dc charger looking at 12-12/30a obviously just keep things from overheating and/or keeping everything in the correct charge profile. thanks.

asked by: Jack

Expert Reply:

Hey Jack, we have chargers designed specifically for this situation with the Redarc BCDC charger part # 331-BCDC1225D this will connect to your truck's charge wiring and will then convert the charge to a voltage that can charge a lithium battery like you have. This is capable of a 25 amp charge. I attached a diagram that shows how this would get wired up for a lithium setup.

expert reply by: Jameson C

Redarc Battery Charger Diagram
(click to enlarge)

Jameson C.

8/7/2025

Hey Jack, how did the Redarc BCDC charger work out for your travel trailer setup? I'm curious if it helped keep your battery charged while powering your 12V fridge during transit. Let me know, as it could help others in a similar situation!