Monday, July 27, 2009

Physics 102. (Roxi)


Amps X Volts = Watts

Who knew there would be a quiz so much later?

Our ultimate goal is to have a small solar set-up installed on the Duck. Even though this is a "green" area, we've had a hard time finding anyone willing to do this around here. Most solar businesses are familiar with the stick home applications, but solar RVing just hasn't caught on in the Northeast.

Instead, we've decided to buy a smallish Honda generator (reviews say the Honda is relatively quiet) for the trip, and have solar installed when we get somewhere. Arizona is crazy with solar technology, and even bigger with RVs.

Batteries: Unless we plan to plug in every night (we don't), we'll need a battery bank. A solar panel or two can keep batteries charged. So can a generator. So can plugging into shore power. [lingo alert] It's the shore power we want to minimize.

But, how much storage do we really need? This is tricky. I know what we need living here in our house - about 10 kilowatt-hours a day. Batteries are rated in amp-hours. What ... ?

(Amps)(Volts) = Watts

I know the DC system is 12 volts. If I wanted to use the same amount of power that I do here at home, I would use 10,000 watt-hours (10 Kwh) every day. If you stick an "hour" on both sides of this equation, you can make it work. I did. Squeeze the math until it cries.

(Amp-hours)(Volts) = Watt-hours

(Xamp-hours)(12volts) = 10000watt-hours

X = 833 amp-hours

So, we would need batteries that could store 833 AH, and would need to replenish them daily, for this kind of load.

But, this is not an experiment in living the same life we live now. What might we really expect to change?

  • propane refrigerator
  • propane range and oven
  • no dehumidifier
  • no cable telephone
  • no sump pump
  • no Ms. Coffee
We don't have a TV now, so I excluded it in the Change list. It's not an issue for us, but it might be for you.

[You see that we are shifting a lot of the energy to propane. I'm not claiming that this is ultimately greener, only that it permits another kind of economy.]

I really think we could get by on much less, maybe the equivalent of 5 Kwh/day. Less? You out there - tell me what kind of usage you've experienced.

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Lora said...

Have you checked out the website? It has a wealth of info for newbies to the rv lifestyle. It's produced by a 40 something lawyer-turned-fulltimer and he tells it like it is. He shares the transition on the "journal" (blog)from novice rv-er to fulltimer. He is also willing to directly correspond with people to help with questions. Also, the forum attached to that website has many helpful and friendly people willing to give advice and encouragement. Just a thought...

The Good Luck Duck said...

Lora, that's a great site - thanks for pointing me there! I went there immediately and started cruising the site ... when I saw that I was logged in. Soon, I found myself reading my own posts! So, this is evidence of how much I lose from one day to the next.

What was I saying?

Anyway, the point is, it's a great site, and it seems to be the most courteous RVing forum I've come across. Thanks for finding it for me (again)!