Running electrical cables

If the battery is the heart of the van, then the electrical cables are its circulatory system. They take power from the battery to where it’s needed, either at 12 volts or via the inverter, which converts 12 volts DC to 120 volts AC to run regular household appliances. 

Making spaghetti - 12v and 120v cables

120 volt cables can be as thin as 12-gauge diameter and still deal with all the power requirements of the van. However, 12 volt cables need to be sized very carefully to prevent them from overheating.

Because the voltage (“pressure” of electricity) is lower, the amperage (“volume” of electricity) that the cable carries has to be higher in order to provide the same total wattage (“energy”). Volts x Amps = Watts. And squeezing too many Watts into a thin cable will make it heat up, and in the worst case melt its housing or start a fire.

Luckily there are online calculators you can use to work out how thick your cables need to be. Most of the cables we ran in the van were fine at 10-gauge (and yes, lower gauge numbers means thicker cables). The lights and some of the lower-power devices could have used thinner cables, and I did use some 14-gauge I had lying around, but if you’re buying a 100-foot reel of cable, it makes sense to use it rather than buying additional thinner-gauge cable as well.

The solar charger has 2-gauge cables, and the run from the battery to the main bus bars and to the inverter is 4/0-gauge (“four-ought”, or four over zero gauge). The wires we used are welding cables. These have multiple strands, which means they are very flexible. It also means they crimp nicely when you want to add lugs to the end to bolt them on to battery terminals.

We also kept the distance between the high-current devices as small as possible. Greater distances also increase resistance, which drops the voltage you receive at the other end as well as wasting the energy as heat.

Once you start using these very large cables, you need tools that can cope with them. Even cutting that many copper strands is hard without a ratcheting cutter.

4/0 AWG cable and a special cable cutter

Crimping is possible with a $15 tool and a hammer, but I decided to buy a $45 hydraulic crimping press. It’s really fun to use and creates very sturdy crimps. Note the interesting translation of the warning sticker. It actually sums up my approach pretty well, I think.

Hydraulic crimping press

Update: We’ve written more now about cable crimping.

8 Replies to “Running electrical cables”

  1. Do you recommend a wire stripper for large gauge cable? Or any suggestions to do this quickly without cutting strands? Your site is THE BEST! Constantly refer to it, thanks for sharing your knowledge:)!

    1. Ryan, we just used a razor blade on the large gauge cable and worked very carefully. Once you’re nearly all the way through the insulation you can normally just pull and it’ll stretch/tear along the line you scored. The cable we used had a layer of paper insulation inside the plastic so it gave a little margin for error.

      Glad you like the site!

  2. Hi again-
    I’m curious about your cable routing strategy– my original plan was to run much[most] of the DC wiring from my fusebox which is behind the drivers seat, up the B-pillar. I’m finding that there isn’t quite as much space as I had planned for and things are getting a little too tight. Did you route your cable up through separate conduit?

    thanks again for all the tips. Couldn’t imagine figuring out much of this on my own 🙂


    1. Oren,
      Our DC cables fan out in all directions from our fuse/distribution panel near the rear of the vehicle. We ran many of the wires inside the walls. In retrospect I think it’s better to try and NOT run through the walls, so I think your B-pillar idea is good.

      We ran separate conduit along the top of the driver’s side wall from front to rear. It contains the factory wiring harness and several of our cables too.

      There are some plastic flanges inside the B-pillar plastic moulding that provide strength for it, but which you *could* trim back to allow more room for the wires.

      If you are prepared to remove both the driver and passenger seat and the seat bases, you can get access to the factory cable conduit that runs between the two seats. Then, you could run cables through that and up the passenger B-pillar for any devices or outlets you wanted on the passenger side of the van. It would reduce the number of cables running up the driver side B-pillar but it would be a pain to achieve.

      Good luck resolving the wiring hell!

      1. oh- interesting. I didn’t realize there was conduit down there. Not sure it is worth the effort, I’m starting to think that adding conduit tight against the back of the pillar may be my best bet for anything I can’t fit. Will see how the next few hours go. Thanks again!

    1. Andy, we used single conductor wire mostly. Any duplex stuff you see is probably leftover 16AWG speaker wire. Mostly you’d be fine running duplex wires. There were a couple of places where the gaps were pretty thin though and single conductor was easier to fish through. The Ancor tinned copper wire is really nice to work with.

      For AC wiring, we just bought some long 10AWG extension cables (surprisingly hard to find) and cut the ends off them. It’s SO or SJ rated stranded cable typically and it’s really flexible to work with. 12AWG would be fine for most uses but we wanted some of it to be rated for 30A circuits.

      1. Got it, thanks, the duplex just seemed easier to run and had the protective sheath on it, but of course is more expensive since it seems to only come in marine grade. I guess I am going to stick to individual wire and just buy a big spool of red and black. Seem like different colors for different things, spar, fans, lights would be cool, but I would end up buying a lot more wire that way. Tx in advance as always.

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