12-Volt Outlets

By , October 24, 2011

I’ve spoken before of the flurry of new projects, small and large changes to our property since Aly went away to college. I refer to it as “Homestead 2.0.” Many of the improvements are ones we’ve intended to make since we moved to the homestead more than 5 years ago. The most significant changes so far have involved the electrical system.

Our cabin lights are 12 volt DC. Our inverter feeds AC power to two sets of outlets in the house, one in the master bedroom on the ground floor, the other upstairs. In addition, we run a cord from the inverter to a power strip in the living room, which we use to power a variety of appliances on an as-needed basis, and to power our many rechargeable batteries.

We’ve always understood a basic irony of consumer electronics: that any tool that requires a bulky power plug, commonly called a “wall wart,” actually runs of DC electricity. The big, heavy plug actually inverts AC to DC for the appliance’s use.

Thus, we convert DC power to AC, plug appliances into that, which convert the AC back to DC. Energy is lost at every step, of course. It’s not an efficient use of power.

For that reason, I’d long planned to install at least one DC “cigarette lighter” outlet in the cabin. Somewhere along my garage-saling way I picked up a 3-outlet set in addition to a single outlet I purchased from a store. I put it off for years, mostly because I couldn’t decide where best to put them. I finally installed the single outlet near the inverter in late August, just days before we took Aly to school. This last week I wired up the 3-outlet set and mounted it in the area where we do most of our AC charging.

I ran a double course of 6 AWG wire—a tad robust for the distance, but it assures almost no voltage drop, and it’s a size I have on hand, so it was free. Since I intend to power my MacBook Pro through these outlets, I wanted to make sure it was more than hefty enough.

I’m extremely pleased with the results. We can now recharge a variety of tools without needing to turn on the inverter. In addition to saving power, it widens the charging “window” considerably. Before, we needed a reason to turn on the inverter. If it were an emergency, we’d turn it on solely to charge, but usually we scheduled charging around other inverter-powered activities, such as using the Internet. Particularly, it’s handy for the cell phones. We can now plug them into DC after we turn them off at night. They’re fully charged and ready to go when we turn them back on in the morning. As the days grow shorter, and our reliance on headlamps increases, it’ll be nice to charge their batteries without needing to turn on the inverter.

I hope to convert a couple of strings of LED Christmas lights to DC this winter. We often see long, dark, calm periods around Christmas, which makes it hard to run the inverter. When we do, its hum detracts from the ambiance. I look forward to quieter Christmases thanks to DC outlets in the cabin.

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