Living off the Grid, Part II: Northern Exposure

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KT: That's right. Power flows from the batteries to the powercenter and then into the batteries. We then draw power from the batteries when we need it.

MOTHER:What purpose does the Powercenter serve?

KT: Mostly it regulates the flow of electricity going into the batteries so that you don't accidentally overcharge them. It also helps to regulate power coming out of the batteries and it also contains a surge protector just in case the solar panels get hit by lightning. An all-in-one powercenter is a very new thing, and it makes installing a home system much easier. (See "How Kip Did It" on page 52 for technical details.)

MOTHER:How often do you have to trek downstairs to check on the battery level?

KT: I'll go down twice a day if we've been running a bunch of appliances. Otherwise once a day.

MEN:How do you know when it's absolutely empty?

KT: It's very simple. The voltage meter on the powercenter is very much like the gas meter in your car. Twenty-five and a half volts is full, 23 is empty, and 24 is about half. The LED meter on the power center can be set to measure battery voltage, input amperage from the solar panels, or what my load or draw-out is. And that's how I know the difference between incandescent lights or how much the coffee maker draws.

MEN:It sounds like you could use all the power generated in one day with just an hour of large-tool use. Is that so?

KT: It would take two hours of continuous use of a heavy tool to dip into savings on the batteries. And a tool is rarely run for that duration of time. I mean, my arms couldn't take it. The planers are the only ones that I can run for a good two hours.

The other day it was rainy and overcast, but I had plastic over the frame so I could still work. When I started, the batteries were at 25.5 volts; when I was done planing by 4 or 5 P.m., they were at 24. But we still had all the lights we needed for the night and the radio in the morning. If they next day was sunny, the system would top out again. If not, I would hold off on the power tools a while or run the generator for a bit.

MOTHER:You have a DC to AC inverter in your system right?

KT: Yes. Solar panels produce DC, but a lot of the appliances in the house will require AC power, so I have an inverter between the batteries and the outlets in the house that changes the 24-volt DC power coming from the batteries into 120-volt AC. It's a snap. Wires come in one side of the inverter and out the other.

MOTHER:You've mentioned the generator a few times. How often does it run to help out when the batteries run low?

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