Date: Sat, 16 Jun 2007 19:57:31 -0700
Reply-To: Michael Elliott <camping.elliott@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Michael Elliott <camping.elliott@GMAIL.COM>
Subject: Re: Solar panels for your Vanagon..
In-Reply-To: <001001c7b055$11e0c380$49b2d8d1@dhanson>
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Hi Don,
Right on. I can't tell if generator people are oblivious, inconsiderate,
or some mixture of both.
To others considering a solar rig, I would suggest using wire thicker
than lamp cord to "remote" the panels. Low voltage systems are high
current systems, so wire resistance wants to be low in order to get as
much power from the panels to the battery. That means fat wire.
Lamp cord is usually pretty skinny stuff, like 22 gauge. A 15-foot
length of 22 gauge has about .36 ohms of resistance (send and return
combined). In my system, the panels might be delivering 4.7A @ 17 volts
in full sun. That's 80 watts. If I were using 15 feet of 22 gauge wire,
the voltage lost due to wire resistance would be .36 x 4.7 = 1.7 volts.
At 4.7 amperes, that's 4.7 x 1.7 = 8 watts lost as heat in the wire, a
10% loss.
Standard North American-style household grade ac receptacles and plugs
are supposed to have less than .03 ohm contact resistance -- when new.
That adds .06 ohm more resistance to the mix, with an additional 1.3
watts of loss.
11% may or may not be important, depending on your system. It's just
something to consider. I wanted the freedom to locate my panels pretty
far from the van, in case the good sunlight isn't conveniently close. I
use 6 gauge wire, and a 40-foot extension. That's just .028 ohm, giving
a loss of .6 watts passive wire loss. The PP75 Anderson Powerpole
connectors have only .0002 ohm of resistance.
--
Mike "Rocket J Squirrel" Elliott
71 Type 2: the Wonderbus
84 Westfalia: Mellow Yellow ("The Electrical Banana")
74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
KG6RCR
Don Hanson typed:
> Solar is the way to go. I agree with Rocket J. Squirrel about having them "remote" from the van..Mine has about 15' of lamp cord hard wired into the panel and the controller. On the van, I have the female half of a regular plug..So that it won't short, from the auxiliary battery that the solar panel supplies. I have mine built into an "A-frame" plywood case.. Deployed to gather sunlight, it resembles one of those sidewalk sign boards you see sitting out front of store, etc. The base of this triangle become a cover for the front of the panel when folded up...All the cord goes inside, wrapped around a couple of cleats. I have a handle on the outside..So, when folded up, it is just a big double sided plywood book and very well protected for packing other stuff without worry of it harming the panel or the controller at all.
> Dunno any of the numbers, but mine easily supplies my lights, my stereo and lap top, charges my cell phone and sometimes runs an inverter powered tool or two. I've spent months at a time in Baja without need of a generator, many times..I have one for the van, one for the Alaskan camper, and my wife just bought a travel trailer, also with a panel that works...until you forget to turn off a light or something...
> I don't know why every RV doesn't use em..You can charge your system chock full when traveling, then when you stop to camp, stick out the panel and it will maintain the charge...But it seems some RVers just love the sound of their own generators...I see em drive into a camp area and immediately start the generator...Often.. We love (joke) this one guy we often see/hear in the desert at a spot we frequent...He fires up his generator outside his travel trailer, then leaves for the day! I asked him.."Hey Walt, how come you start your generator and leave?" He says, "I don't like all the noise"...Clueless!
> Don Hanson
>
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