How to wire electrical

ReluctantTraveler

Active member
Is there a canonical resource on how to wire electrical in a DIY camper? I've found a bunch of resources on the web, but nothing I view as a must-read for overlanders/expedition rigs.

If it helps at all, for my build I'm looking to include...
  • A DOMETIC RTX 2000 12v AC
  • 12v fridge
  • Maxxair fan (or two)
  • A portable induction range
  • A propane furnace
  • A TV or two
  • A bunch of outlets (110 and USB)
I want to be able to run for at least a few days off battery, with charging via solar, the truck's alternator when driving, and shore power. I know I'll need an inverter to power my 110 outlets from the battery bank.

From my various reading, it sounds like I could either bypass the batteries for shore power when plugged in, or use shore power ONLY to charge the batteries, and run everything off of them all the time. I'm not sure which one is better.

I'm also not sure how you determine what size fuses/breakers you need (for 12v and 110, respectively) or gauge of wire. The camper will need lights tied into the car's lights. Is there a plug-and-play solution for that? Basically, I'm feeling very overwhelmed by this part. Everything else about the build seems manageable.

Those of you who've built your own rigs: did you DIY the electrical, or hire an electrician to wire it up for you?
 

Herbie

Rendezvous Conspirator
There are a LOT of questions here, probably too many to answer directly, but let me start here:

RULE #1: AVOID SETTING YOUR RIG ON FIRE

If you keep Rule #1 in mind while making all your other decisions, things get more clear.

Rule #2 You size the Fuse to the Wire - the fuse is to protect the wire from burning up if it gets short-circuited to ground. (See Rule #1) This means the fuse should be as close as possible to the current source (battery, etc.) as practical. A fuse 3-feet down the wire doesn't protect you from a short 2-feet from the battery!

Rule #3 You size the Wire to the Load.

Look in your user/installation manual for the AC. If your AC pulls 15A, you need a wire that can handle 15+ Amps (plus margin). You will want to find a "Wire Ampacity Chart" - study it carefully as different kinds of wire (and different operating temperatures) confer a lot of different current-carrying capabilities. Again, remember to build in margin - if you use a 15A wire for a 15A load, things could eventually get hot and melt the wire (or pop the fuse). So for a 15A load, I suggest a minimum of 20-30A current carrying capacity.

Repeat the above steps for each and every load in you intend to support.

Add up all the loads - 15A for the AC, 7A for the furnace, 10A for the USB outlets, etc. etc. and this will tell you your max amperage load. You may not use all of these things at once, but you need to keep in mind the total load. If you run a big cable from the battery to a fuse box, that cable needs to be big enough to support all potential current at the same time. (See Rule #3, and Rule #1)


Rule #4 You size the battery to the total load. You should by now know how much current you expect to use for each thing - multiply those by how many hours you expect each thing to run, and add those up - that's your total Amp-Hours needed. Now go learn about battery capacity - some chemistries (AGM) can only be safely discharged to 50%, so take your total AH-needed and double it. LiPo, etc. is more forgiving. Do the math to know your capacity vs. need.

How will you charge your battery?

Rule #5 You size the charging systems to the Battery and the Total Load. Your battery is just short-term storage - anything you plan to take out, you have to put back. There are a number of ways to do this, so you'll need to figure out what's right for you (Solar, Alternator, DC-DC, Generator, etc.) based on, you guessed it, more math.
 
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NatersXJ6

Explorer
I don’t disagree. I’m also someone who just likes to understand how my whole setup works.

Any good resources for that?

I started learning by burning down wiring harnesses in old cars when I was a teenager trying to get better stereos and keep my old junk running. I don’t recommend it!

Over the years, I’ve refined a lot of that knowledge by reading everything I possibly can, including a lot of really good info here in the Power Systems sub-forum.

I can’t recommend a specific book, but… don’t laugh…

Snap Circuits are a great and fun way to learn the extreme basics of electricity and electronics if you are starting from zero.
 

ReluctantTraveler

Active member
I started learning by burning down wiring harnesses in old cars when I was a teenager trying to get better stereos and keep my old junk running. I don’t recommend it!

Over the years, I’ve refined a lot of that knowledge by reading everything I possibly can, including a lot of really good info here in the Power Systems sub-forum.

I can’t recommend a specific book, but… don’t laugh…

Snap Circuits are a great and fun way to learn the extreme basics of electricity and electronics if you are starting from zero.

it didn’t occur to me that power systems meant electrical etc. thanks!
 

ReluctantTraveler

Active member
There are a LOT of questions here, probably too many to answer directly, but let me start here:

RULE #1: AVOID SETTING YOUR RIG ON FIRE

If you keep Rule #1 in mind while making all your other decisions, things get more clear.

Rule #2 You size the Fuse to the Wire - the fuse is to protect the wire from burning up if it gets short-circuited to ground. (See Rule #1) This means the fuse should be as close as possible to the current source (battery, etc.) as practical. A fuse 3-feet down the wire doesn't protect you from a short 2-feet from the battery!

Rule #3 You size the Wire to the Load.

Look in your user/installation manual for the AC. If your AC pulls 15A, you need a wire that can handle 15+ Amps (plus margin). You will want to find a "Wire Ampacity Chart" - study it carefully as different kinds of wire (and different operating temperatures) confer a lot of different current-carrying capabilities. Again, remember to build in margin - if you use a 15A wire for a 15A load, things could eventually get hot and melt the wire (or pop the fuse). So for a 15A load, I suggest a minimum of 20-30A current carrying capacity.

Repeat the above steps for each and every load in you intend to support.

Add up all the loads - 15A for the AC, 7A for the furnace, 10A for the USB outlets, etc. etc. and this will tell you your max amperage load. You may not use all of these things at once, but you need to keep in mind the total load. If you run a big cable from the battery to a fuse box, that cable needs to be big enough to support all potential current at the same time. (See Rule #3, and Rule #1)


Rule #4 You size the battery to the total load. You should by now know how much current you expect to use for each thing - multiply those by how many hours you expect each thing to run, and add those up - that's your total Amp-Hours needed. Now go learn about battery capacity - some chemistries (AGM) can only be safely discharged to 50%, so take your total AH-needed and double it. LiPo, etc. is more forgiving. Do the math to know your capacity vs. need.

How will you charge your battery?

Rule #5 You size the charging systems to the Battery and the Total Load. Your battery is just short-term storage - anything you plan to take out, you have to put back. There are a number of ways to do this, so you'll need to figure out what's right for you (Solar, Alternator, DC-DC, Generator, etc.) based on, you guessed it, more math.

this was supremely helpful! Rule #1 is why I’ve considered just hiring a pro.
 

Herbie

Rendezvous Conspirator
I suspect you will struggle to find a “pro” on the 12V side unless you look at the Marine world. If you are near an Ocean or the Great Lakes it might be a bit easier.
That used to be true, but in my area at least, I'm seeing more businesses specifically catering to the "Overland" crowd with a specific focus on wiring and electrical installation. Some are standalone and some are general overland/4x4 type shops that have expanded their services.
 

clintium

Member
I was where you were like 6-12 months ago and I agree it's just exhausting and overwhelming to get started. Eventually I just ordered all the pieces and started putting them together. It's overall pretty simple if you're DIY inclined and like learning about this stuff. But if you really don't have the time or energy to learn to do it safely I definitely recommend paying someone.
 

1000arms

Well-known member
... The camper will need lights tied into the car's lights. Is there a plug-and-play solution for that? Basically, I'm feeling very overwhelmed by this part. Everything else about the build seems manageable. ...
Instead of connecting a trailer to your truck (and using the appropriate electrical connectors), you will be connecting your camper to your truck (and using the appropriate electrical connectors).

Connecting any camper house batteries to your truck alternator(s) will the same as connecting any trailer house batteries to your truck alternator(s). (Additional, but heavy duty, wiring and connectors.)
 
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ReluctantTraveler

Active member
Instead of connecting a trailer to your truck (and using the appropriate electrical connectors), you will be connecting your camper to your truck (and using the appropriate electrical connectors).

Connecting any camper house batteries to your truck alternator(s) will the same as connecting any trailer house batteries to your truck alternator(s). (Additional, but heavy duty, wiring and connectors.)

I was thinking specifically about the "in camper" part. I noticed the IdaCamper plugs in just like a tailer.

It'd be awesome if there was a box you could just plug the camper lights into to wire them up. I'm sure there must be.
 

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