Best Way To Charge A Lithium Battery With A 7-Pin Trailer Plug On A 2021 Ram 2500
Updated 12/08/2025 | Published 11/19/2025
Question:
Good Morning, I am wiring up my enclosed trailer with 50amp RV service using a progressive dynamics 4590 and using a 100ah LifePo4 lithium battery. My question is, how should I wire in the charging wire from the vehicle 7 pin trailer plug? Is it as simple as the power wire from 7 pin to positive of battery? And positive from battery to pd4590? Obviously Ill install a couple inline fuses as well. Been reading too much on the vehicle not being able to charge lifepo4 battery correctly or the lifepo4 over running the vehicle battery and kills vehicle batteries. Vehicle is a 2021 ram 2500 6.7 diesel with tow package and factory trailer brakes.
asked by: Joe B
Expert Reply:
Hey Joe, great question. You’re thinking about it the right way. You can technically run the charge line from the 7-pin’s 12V power wire straight to the positive post on your battery, but with lithium you’ll want to do it safely. Your truck’s alternator and factory charge line aren’t designed for lithium charging, and without control, the battery can either overdraw or back-feed to the truck.
To fix that, install a DC-to-DC charger like part # 331-BCDC1225D between the 7-pin charge wire and the battery. That keeps current flow safe in both directions and ensures proper voltage for the lithium battery. You’ll still run your positive from the DC-DC charger to the PD4590 and your negative back to the frame or ground bus, with inline fuses on both ends. That setup will keep your lithium battery and truck system protected while charging efficiently.
(click to enlarge)
Product Page this Question was Asked From
Redarc In-Vehicle BCDC Battery Charger - Dual Input - DC to DC - 12V/24V - 25 Amp
- Battery Charger
- Battery Charger
- RV/Camper
- Trailer
- 12V
- Charges and Maintains
- AGM
- Calcium
- Gel
- Lead Acid
- Lithium
- Solar Panels to Auxiliary Battery
- Vehicle Battery to Auxiliary Battery
- Smart Charge
- Trickle Charge
- Redarc
more information >
Featured Help Information
Instructions
Continue Researching
- Shop: Victron SmartShunt Battery Monitor - 300 Amp
- Shop: Victron VE.Direct to USB Interface
- Shop: Victron SmartShunt Battery Monitor with IP65 Protection - 500 Amp
- Shop: Devos LightRanger Motion Sensor
- Shop: Victron GX Touch 50 Display for Cerbo GX Communication Center - 5" Touchscreen
- Search Results: anl fuse
- Search Results: torque wrench automotive tools
- Search Results: victron smart shunt
- Shop: Victron Lynx Shunt VE.Can with Built-In Battery Monitor - M10
- Shop: Victron Lynx Shunt VE.Can with Built-In Battery Monitor - M8
- Search Results: victron
- Search Results: victron multiplus
- Search Results: victron inverter
- Q&A: How To Attach Loose Wires to Class T Fuse Block for Go Power Inverter
- Search Results: rv power converter
- Video: Review of Victron Battery Charger - Blue Smart 12V Battery Charger With Bluetooth - VN65ZR
- Video: Hands-On Review with the Big Truck Big RV Trailer Tongue Weight Scale
- Shop: RV Power Cord
- Video: Review of BTBRV Tongue Weight Scale - BTBRV004
- Video: Review of Go Power Battery Charger - PerfectPower Battery Charger 12V DC - GP95QR
- Q&A: DC to DC Battery Charger Kit Recommendation for a Scamp Trailer
- Video: Review of P and F Products Trailer Trim - Top/Bottom Edge - PF36FR
- Video: A Closer Look at the Andersen Camper Wheel Chock and Leveler
- Video: Review of the Quick Disconnect Propane Hose
- Q&A: What is the AUX Power Pin for on a 7-Way Trailer Connector
- Shop: RV Camera
- Q&A: Best Weight Distribution System for a Forest River Rockwood Geo Pro G19FD
- Q&A: Recommended Weight Distribution System for a 4,000 lbs Trailer
- Shop: Suspension Enhancement
- Q&A: Can I Charge My Trailer Battery Using 7-Way Trailer Connector on Truck
on Battery Charger
Jesse M.
12/8/2025
Hey Joe, how did things go with adding the DC-to-DC charger between your truck’s 7-pin and the lithium battery? It’d be great to hear if that setup kept your charging system stable. Your results could really help others wiring similar trailer setups.