Date: Sun, 17 Jun 2007 09:36:58 -0400
Reply-To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject: Re: Solar panels for your Vanagon..
In-Reply-To: <4674A31B.3030306@gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Lamp cord should be 18 gauge. Still to small for high current solar
systems.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Michael Elliott
Sent: Saturday, June 16, 2007 10:58 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Solar panels for your Vanagon..
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
>
|