# Battery bank question



## trapperJim (Jan 24, 2008)

When running a cabin on a battery bank with a power inverter, is the cabin wired in (normal) fasion with 14/2 or 12/2 wire and common outlets?


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## Sand Flat Bob (Feb 1, 2007)

The wire size should be based on the amp load of the lights, or other device you are suppling power to. Roughly figure that No. 14 wire will carry 15 amps. No. 12 wire will carry 20 amps. Since you are in a cabin, assume all runs are very short, less than 50 feet. The above will give you a small safety factor. Wire size is dependent on amps. The voltage is not important in sizing wiring as long as it is below 600 volts. This is greatly over simplified, but it will work safely.

Good luck,

Bob


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## deaconjim (Oct 31, 2005)

I'm more inclined to oversize a little. To be honest, I can't remember ever buying any 14/2 for anything. I would use the 12/2 w/ground, regardless of whether it was commercial power or a battery bank. The 12/2 will have a lower resistance, resulting in lower line losses (even though the line losses are small in either case).


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## WisJim (Jan 14, 2004)

To answer what I thnk is your original question, yes, you would wire it just as if it had "normal" 120 volt AC grid power, for all the outlets/fixtures powered from the inverter. Your breaker box gets its power from the inverter, instead of the grid, and everything on the house (load) side of the breaker box could be wired like a "normal" house. I would also agree that using 12 gauge wire minimum makes sense.


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## trapperJim (Jan 24, 2008)

Thank you for the replies. I lived off grid back in the 80's and am headed that way once again but want to be a little more (adavanced) this time around. I have a lot to learn about battery banks and solar etc. From what I'm gathering from your replies, my set up should be as follows:

Batteries >> to inverter >> to breakerbox. 

If I want to have it so that I could power up the place with a generator occasionally to operate power tools and such, is there a *simple* process to bypass the inverter so that I can power up the house straight from the generator without disconnecting the inverter?


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## Gary in ohio (May 11, 2002)

The answer to your question is YES. Wire it as you would any other home. The source of the 110v power be it 1kw inverter or megawatt nuke plant is the same power. People sometimes forget that a alt power system can still kill you.


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## wy_white_wolf (Oct 14, 2004)

Wiring for everything that you want 120v would be the same. Batteries > inverter > breaker box.

The difference comes in if you want any DC loads. They would run off the batteries to a load controller (shuts down when voltage drops too low) and then to a DC breaker box. Then all wiring must be sized to handle the expected load on it and its length.


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## greg273 (Aug 5, 2003)

Oh, dont forget the charge controller between the panels and the batteries. And DC-rated disconnects (SquareD 'QO' line is one) between darn near everything...
Yeah, theres some learning involved, but all in all its a satisfying expierience to know your electricity is coming from sunlight.
Heres a simplified path...
Panels > PV disconnect/breaker > Charge controller > Disconnect/Breaker> Batteries > Disconnect/Breaker > Inverter > AC Load Center> Outlets


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## greg273 (Aug 5, 2003)

wy_white_wolf said:


> Wiring for everything that you want 120v would be the same. Batteries > inverter > breaker box.
> 
> The difference comes in if you want any DC loads. They would run off the batteries to a load controller (shuts down when voltage drops too low) and then to a DC breaker box. Then all wiring must be sized to handle the expected load on it and its length.


 Thanks for mentioning the 'load controller' on the DC side, I almost forgot about that one! WHen my water system is up and running, it will be a 24volt DC pump. And I will have a 'spare' C-40 controller when I get the new MPPT controller. I guess I could put the C-40 inline to prevent over discharge of the battery bank if somehow a pipe ruptures when I am away or something. I would hope that the pump would simply overheat first, before draining down the battery bank, but i dont know...
Probably the best option would be to shut the power off to the pump before I leave the house!


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