We Go Solar

20 09 2010

Take my word for it that connecting the last cable in a solar setup is so freaking cool. Going from charging off of an alternator or a generator to charging off of a big ball of fire in the sky is awesome.

We picked up two 60 watt solar panels a few days before Burning Man. Having found them on Craigslist, we got an awesome deal from a guy who needed to quickly relocate to Seattle, not knowing what to do with the gazillion panels he had powering his house and – get this – his remote weather stations. Not only did we pick up two panels at a sick price, but as we were about to drive off the seller came running out…. to give us a charge controller – the ~$125 piece of equipment that knows what to do with the juice from the solar array. Sweet.

A trip to Lowe’s and a quick-and-dirty lesson in wiring from Dave in the electronics section left me with a lot of equipment and an able-but-wary feeling that I could make our panels suck up the Sun’s magic and somehow get it into our battery without blowing anything up.

Enter Burning Man: Six days in the desert (actually, we stayed for eight) with beautiful beautiful sunlight all day long. What better a place to give solar power a go?

Here’s what you need to know about how a solar setup works (Only if you actually care to understand it. Otherwise skip the bullets.)

  1. We have a deep-cycle coach battery that has a certain capacity. Think of it as a fuel tank that holds a certain amount of fuel.
  2. When the RV draws current from the battery, it depletes that fuel.
  3. ‘Fuel’ usage is measured in amp hours. If a load draws one amp for one hour, the ‘fuel tank’ is has been depleted by one amp hour. If a load draws five amps for a half hour, you’ve used 2.5 amp hours of ‘fuel’. (Theme: amp hours used = draw in amps * duration of draw in hours.)
  4. Deep cycle batteries are meant to be discharged to most of their capacity without adverse impact to the battery’s life span. (Within certain parameters.)
  5. But wait! If you discharge the battery, you probably want to recharge it.
  6. Enter solar! Our solar array can put out ~7 amps at best, so following what we learned in item #4, if the panels deliver 7 amps for one hour, we’ve replenished 7 amp hours of ‘fuel’ (which we’ll stop calling fuel…)
  7. It gets more complicated. Our panels put out 17.1 volts, but our battery will fry if it gets that much voltage. At different points in the charging process the battery needs different voltages, usually in the 13v to 14.5v range.
  8. Enter charge controller! The charge controller takes whatever current and voltage it’s receiving, figures out what the battery needs, and delivers it while displaying data on what’s going on.

So where do things stand? Setting up solar at Burning Man was fun. I put together a mobile panel array with fifty feet of cabling from the panels to the controller. That way the panels could be out of the way and could be angled toward the sun for best possible exposure.

Our (Very Temporary) Solar Array At Burning Man

Our (Very Temporary) Solar Array At Burning Man

But a mobile setup isn’t convenient for RVing in the city. It takes time to set up and isn’t conducive to us leaving the RV (and panels) unattended. The obvious solution is to mount the panels on the RV’s roof. I’ve struggled over whether to do the project myself or to have the panels professionally mounted. I’m leaning toward the latter, but am working on figuring out the best way to make it happen. I don’t mind paying the few hundred dollars for labor (and knowledge!), but I’m also considering pitching a barter arrangement where the technician would do the install and I would give them some of my time working around their shop. There’s certainly more to come on this.

[Oddly enough, just as we’re moving forward on solar we’re at our first spot in six weeks where we’re plugged in to shore power. Ah, the irony.]

posted by jay




4 responses

20 09 2010

Awesome. I’ve been thinking about doing the very same thing to The Falcon. Now I’ve got someone’s brain to pick on the subject! Best of luck with the roof install.

To Simplify…

21 09 2010

Thanks! I’m a bit new to things, but have a pretty good idea as to how it all comes together. Shoot me an email if you have any questions.

21 09 2010

Yeah, solar is a good way to cut back on your expnses when you’re out on the road. Upfront cost yes, but savings over the long run. Look forward to hearing more when you get the panels up on the roof.

21 09 2010

And I’m looking forward to seeing the panels on the roof! I’m definitely looking at solar as a long-term way to cut back on expenses.

(I actually think we may have already broken even. We picked up our panels for an unheard of $1.50 / watt, so resale should be pretty fun.)

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