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Small Cabin Forum / Off-Grid Living / 12V Wiring for Dummies
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montecristo
Member
# Posted: 12 Dec 2018 17:39
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I've done standard house wiring before, but 12V DC seems to be a whole new thing.

I'm looking to run about 6 lights, a couple phone charging banks and 1 or 2 ceiling fans with the 12V system. The batteries would be charged from a generator but would like the possibility to convert to solar at some point in the future.

I would also have a couple 110 AC receptacles that would run off of a generator for larger items if the need arises.

Does anyone have any good resources/links to help me out with this? I am just trying to get a plan in place for the cabin that I will be starting to build in the spring. I'd like to keep it as simple and inexpensive as possible but don't really know where to begin.

montecristo
Member
# Posted: 12 Dec 2018 18:29
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I'm guessing I need to do something like this system, without the solar components.
Inkedoff_grid_solar_.jpg
Inkedoff_grid_solar_.jpg


Atlincabin
Member
# Posted: 12 Dec 2018 18:51 - Edited by: Atlincabin
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Works same as regular wiring and plumbing - stuff comes in one tube/wire and out the other tube/wire. I had an off-grid house we built in the 80s that had a primitive (by today's standards) solar system. Most of the time power was run through an inverter and the house ran on 110V, but when we had electronic issues, I could change over and use 12V bulbs and other small appliances when necessary, using the same wiring.

What you have in the diagram should work ok, just keep the batteries topped up above about 75-80% or they will have a shorter life. I would buy an "all in one" unit that contains the charge controller and inverter and battery charger now, so it would be relatively simple to add solar panels as you have the time and resources. You could include an automatic switchover (generator starter), or just wire in a manual switch (simpler and cheaper, but not automatic).

My two cents.

paulz
Member
# Posted: 12 Dec 2018 19:35
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Quoting: montecristo
I'm looking to run about 6 lights, a couple phone charging banks and 1 or 2 ceiling fans with the 12V system.


I'm running all that from 12v. I'm using all 110v cords, wall plugs, etc. 5v phone/tablet chargers made for cars by Anker. Just careful of polarity. I have no 110 to make it confusing.

razmichael
Member
# Posted: 13 Dec 2018 07:48
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As others have noted, it is not really that different. I remember finding 12 Volt Side of Life a very useful reference (with part 2 as well) although now very old. My cabin is mostly 12V although I also have 120V outlets run off an inverter (which is normally not on). Generally I used 120V wiring throughout so I could convert in the future. Given the improvements in technology (and drop in costs) I would likely just go 120 if I was doing it today. My inverter also acts as a transfer switch if I hook up the generator (and a smart charger) as mentioned by Atlincabin. Normally the solar handles everything.
The main concern with 12v is the voltage drop if you are running anything a longer distance - lots of calculators to check this out, and some ways to reduce the impact if needed.

montecristo
Member
# Posted: 13 Dec 2018 09:18
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So I can wire the cabin like I would a house (with 12-2 wire) to a breaker panel? Both the generator and battery bank would connect to an inverter that would connect to the breaker panel?

Am I thinking this right? Just seems like so much conflicting info on google.

Does anyone have a recommended inverter that would work well for what I am trying to accomplish?

Atlincabin
Member
# Posted: 13 Dec 2018 10:32
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That is correct. The assumption at this point is that everything in the cabin is run through the inverter and is running on 110V. You will need wall warts to convert back to DC and/or lower voltage to charge things like phones etc.

I've gotten several solar systems and parts from the folks at Wholesale Solar (out of California). Lots of info on their website. They can custom design something if you don't find something you like. And there are other vendors out there that have similar systems available. Most any of the inverters from reputable dealers should work ok. I've used Magnum, SolarEdge, and SunnyBoy inverters. Schneider is recognized as a good brand as well. And there are several others.

offgrididaho
Member
# Posted: 13 Dec 2018 13:20
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An inverter/charger can make the wiring easier... basically it's how it sounds, one device that inverts DC to AC current and also a charger to charge the batteries from the generator.

Check out Victron inverter/chargers as example of reputable company's products (there are others out there):
https://www.victronenergy.com/inverters-chargers

paulz
Member
# Posted: 14 Dec 2018 13:58
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Question: My cabin runs off my truck, 3 deep cycle batteries in paralell. The cord that reaches my cabin is about 50 ft, big 220v cord, 10g I think. The volt meter at the truck always read .1-.2v higher than the one in the cabin. Is it costing me battery power? What about inverting to AC at the truck and back at the cabin?

Atlincabin
Member
# Posted: 14 Dec 2018 17:53
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There are line loss calculators online. Here's one:

https://www.calculator.net/voltage-drop-calculator.html

Input your voltage, wire size, and distance and they will calculate your voltage drop. Using your numbers yielded 0.16V drop for a 1 amp load. So it's not surprising that you see a bit of difference from the truck to the cabin. Yes, it costs some power, lost primarily as heat (though you are unlikely to be able to feel that heat in the wire).

toyota_mdt_tech
Member
# Posted: 15 Dec 2018 08:51
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How about wiring it std AC voltage and add everything you want, then use an inverter to supply 110VAC from 12V bank, any size you want and also be able to use a solar charge controller for your 12V batterys in the future. You can buy a few of those outlets that have the USB charging ports in them now.

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