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All DC 12 Volt systems
May 29, 2012
5:36 am
Forum Posts: 6
Member Since:
November 14, 2011

So, I've been helping a friend (who shall remain nameless) with his cabin on and off over the past few years. He had the option of connecting to the grid for $20-25,000 plus monthly fees and of course ongoing electricity charges and decided (before I ever got involved) that since he was there less than once a month he would be far better off simply buying a generator and paying for a large tank of LP to fuel it. From a cost standpoint I think this was a pretty good thing to do – but it very much set him down a path that I think wasn't in his overall best interest and has cost him far more than his system needed to cost.

In particular I think he ended up building a cabin that wants to be connected to the grid. Of course, the cabin itself doesn't care, but all of its orientation is toward feeling and acting like a house connected to the grid. There's a microwave he brought up after he upgraded one at home, a home stereo system a friend was getting rid of, and mostly there's an amazing array of lighting both inside and outside. Having a generator on site that produced 120V Alternating Current made all of this seem very easy and reasonable. I also think it was all wrong.

Last year he decided that he wanted a battery array because the generator was too loud to run at dinner or at night when he wanted to use lights. His battery system cost essentially as much as his generator in part because it includes a giant inverter so that either the generator or his battery array can power the entire cabin as if it were connected to the grid. In all fairness there's no "additional" fuel cost associated with that investment, nor will there ever be and at some point he can replace the generator with a PV array and eliminate all fuel costs.

But the bigger issue for me is that his cabin is not connected to the grid. Unfortunately, since the entire house was wired for AC already he needed the battery/future solar system to be able to provide it.

If instead of going AC at the start he had opted for a 12V Direct Current system he could have avoided the inverter and a generator sized for peak load to say nothing of the inefficiencies of converting DC from the battery/PV system into AC (and in the case of his laptop and cell phone, back into DC again). If he really felt like some kind of generator was necessary he could have invested in a small generator that topped off his batteries rather than tried to meet peak load.

But what would he be giving up? Very little, it turns out: LED lighting runs on DC and there is a very large spectrum of 12V DC lighting that is available, prices keep coming down and the selection of lights keeps getting better and better. His home stereo could have just as easily been a car stereo. And it turns out there's even a DC microwave (** you don't have permission to see this link ** – no endorsement here, just pointing out that it exists) that can run enough power to pop popcorn (because nothing says city living like microwave popcorn).

I'd love to hear more about anyone's 12VDC off grid systems. Do you use an inverter for certain appliances or not at all? Are you charging from a 120V AC source or straight DC?

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