12V inverter wiring question

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12V inverter wiring question

Postby Mr. Lahey » Sat Oct 15, 2016 9:04 am

I have some light duty 110V items I wish to run off a 12V inverter. I would like to have one outlet in the trailer bed cabin and one outlet in the galley. Will use a 1000 watt or smaller inverter. Very small 110V loads will be used.

My question is should I place the inverter in my rear bulkhead area and run long massive 12V cables to it from my front mounted battery?

Or should I mount inverter near battery, and distribute the 110V power from inverter with regular 110V Romex cable to the desired outlets?

What's the best way to do this?
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Re: 12V inverter wiring question

Postby daveesl77 » Sat Oct 15, 2016 11:59 am

If possible, mount the inverter as close to the battery as you can. 12v DC requires much larger wiring to compensate for voltage drop than does 120v AC. Thus, put the inverter close to the battery and use large cable to connect the two. Then the 120V side can drop down to extension cord size wiring. Be aware that an inverter might be 80%+/- efficient, meaning that for something requiring 800 watts to continually operate, it can take perhaps 1000 watts of input power to develop that. 1,000 watts at 120 v is essentially 8 amps, but at 12v is 80 amp. For my 2,000 watt inverter I ran #00 battery cable 3 feet from the battery (tongue box) to the inverter (inside front wall). I have nothing that fully taxes that inverter.

That is actually why Edison lost out to Tesla/Stanley/Westinghouse in having the U.S. being a DC or AC country. It was called the "War of the Currents". Edison wanted lots of little generators all over the place (he held the patents), while with the alternator and transformer (Tesla/Stanley/Westinghouse) for AC you could go with only a few high voltage power stations and thus much smaller wiring and far more distant transmission areas. Edison did a major PR campaign to try to terrify people into not using the high voltage system, but it backfired on him.

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Re: 12V inverter wiring question

Postby troubleScottie » Sat Oct 15, 2016 3:28 pm

To the Tesla/Edison thing, AC can be easily transformed from one voltage to another. Transformers are very simple electrical devices. The winding difference determines the voltage change.

This ability to be transformed helps with transmission which requires higher voltages for distance and the reduction at the customer end (back to 110/120 V).

DC does not radiate. AC does radiate. That is why AC is at a low frequency. High frequency would make the power lines just big antenna radiating the power away. Hence the compromise of higher voltage, low frequency AC.

Also to the same point, to run 10 ft of AC cable is really not bad given the correct gauge wire. One's house may have 100+ foot wires with no noticeable loss of power at the outlet. From my electrical panel to the farthest outlet is over 150' (small, multi-story house). One would have to be concerned about a similar DC run.
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Re: 12V inverter wiring question

Postby Mr. Lahey » Sat Oct 15, 2016 8:53 pm

Thanks guys!

Had a hunch it was best to run the long wires with the AC current instead of DC.
Nice to have some confirmation on that.

So it shall be. Back to work I go.
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