600 AH Electrical Build on 2015 Ram Promaster 2500
November 26, 2025
How I Wired My 2015 Ram ProMaster 2500 Camper Van (Full Electrical Build + Parts List)
Disclaimer: I am not a professional electrician. This post is simply a walkthrough of how I wired my 2015 Ram ProMaster 2500. Always double-check wire sizes, fusing, and installation techniques, and consult a qualified electrician if you’re unsure. Some of my early wiring diagrams had wire sizes that I later upgraded, so do not treat my diagram as professional advice.
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I bought my 2015 Ram ProMaster 2500 for $8,500 and turned it into a rolling cozy cabin with a full off-grid electrical system: solar, alternator charging, lithium batteries, inverter, shore power, and more. In this post I’ll walk through my setup, the parts I used, and a simple wire gauge cheat sheet so you can start planning your own system.
1. The Heart of the System: 600Ah of LiFePO4 Batteries
The core of my system is 600 amp hours of lithium power, built with two 12V 300Ah LiFePO4 batteries. That’s a ton of usable power for a van — enough to run lights, fridge, fans, outlets, and even heavier loads when needed.
Wire Diagram (double check wire guages)
PUPVWMHB 12V 300Ah LiFePO4 (x2 for 600Ah total)
🖤 Buy Battery on Amazon
Quantity: 2
Type: 12V 300Ah LiFePO4
Use: Main house battery bank powering everything in the van
The batteries are mounted securely inside the van and connected using properly sized cables and lugs. Always make sure your batteries are secured so they can’t move in a crash or hard turn.
2. Inverter / Converter: Turning 12V into 120V
With a big battery bank, I wanted the ability to run standard 120V household devices. That’s where the 2000W inverter comes in. It turns 12V DC battery power into 120V AC power.
Chargers for laptops, cameras, and other electronics
Small appliances (within reason for 2000W)
The inverter is connected directly to the battery bank using 2/0 gauge cable and properly sized fuses to handle the high current on the 12V side.
3. Shore Power: Plugging the Van into the Grid
Even with solar and alternator charging, sometimes it’s nice to just plug in. I added a NOCO AC inlet port on the outside of the van so I can connect to shore power when I’m at a campground, driveway, or shop.
One important part of this build is that I grounded both the 12V system and the 120V system to the van chassis. The chassis acts as a common reference and fault path.
Key points about my grounding:
Main 12V negative from the battery bank is bonded to the chassis at a solid, cleaned metal point.
The 120V system (through the inverter) has its ground tied into the chassis as well.
Paint was removed at the grounding points, and star washers were used to bite into bare metal for a solid connection.
If you’re not sure how to properly bond your AC and DC grounds, talk to a professional. Getting grounding wrong can be dangerous.
10. Wire Gauge & Distance: Why Size Matters
One thing I want to be very clear about: some of the wire sizing in my early diagrams was not ideal and I corrected it later. Don’t blindly copy a diagram (including mine). Instead, think about two things for every wire run:
How many amps will flow through this wire?
How long is the wire (one-way distance)?
On a 12V system, low voltage means you need thicker wire to carry the same power. And the longer the run, the more voltage you lose (called voltage drop). The more voltage you lose, the more heat you build in the wire and the less power actually reaches your devices.
Quick 12V Wire Gauge Cheat Sheet
(These are rough, conservative guidelines. Always use a proper wire size calculator for your specific setup.)
Amps
Approx. Distance (one-way)
Suggested Gauge (AWG)
1–5A
0–15 ft
16–18 AWG
5–15A
0–15 ft
12–14 AWG
15–30A
5–10 ft
10 AWG
30–60A
5–10 ft
6–8 AWG
60–100A
3–6 ft
2–4 AWG
100–300A
1–5 ft
2/0 AWG
Simple rule of thumb: If you’re unsure, go thicker. Undersized wire is dangerous; oversized wire is safe (just more expensive).
11. Extra Parts That Made the Install Easier
These aren’t the “core” components, but they made the installation cleaner and more flexible:
Between all the major components, wiring, fuses, breakers, and extras, my total electrical cost came out to around:
Final Total: $2,263.25
For a 600Ah lithium system with solar, alternator charging, shore power, and a 2000W inverter, that’s still way cheaper than paying someone to install a comparable system.
Final Thoughts
This setup has turned my $8,500 Ram ProMaster 2500 into a legit off-grid tiny home on wheels. It’s not perfect, and I’m always tweaking things (including wire sizes and layout), but it works and it’s taught me a ton.
Again, I’ll repeat the warning: I am not a professional electrician and this is not professional advice. Use this post as inspiration and a parts reference, but always double-check your designs and code compliance.
If you want a downloadable wiring diagram, checklist, or a more detailed breakdown of each circuit, let me know and I’ll put together a version you can print and take into the van with you.
