Date: Sun, 17 Jun 2007 08:58:51 -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: <d0c.128354cc.33a672e8@aol.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Hi Frank, I can't help with solar panel brands help. Near as I can tell,
all the major manufacturers have to meet domestic and international
standards for durability, and they do the best they can with efficiency
-- read the specs. I tried to find the most Watts per square foot, but
the variations among the good manufacturers are not big.
I got two 45-watt BP Solar panels instead of one big panel because a.
two panels are lighter and easier to handle than one big one, b. if one
breaks I have a backup, c. laid flat and stacked atop each other they
fit where the upper bunk used to live when the top is down. As mentioned
before, I don't mount the panels on the roof because where the sun is
and where I want to park are not often the same. I use simple camera
monopods mounted to the rears of the panels to prop them against, and
angle them as needed to follow the sun.
The Koolatron will want 3Ah to operate. During dark hours (six of them,
you say?) that's 18Ah. Group 41's are, what? 60Ah or so? So you'd use
30% of the battery's capacity. Add in the other appliances (lighting,
etc.) that you want to use after dark and you'll see how deeply you are
digging into the battery's capacity. The more deeply you repeatedly
discharge the battery, the shorter its life, but if you're not using
expensive batteries, just dispose of the old in a responsible fashion
and drop in a new.
During the day, the panel will need to run your appliances, the
Koolatron, and put that energy back into the battery. A 120W panel
should be good for at least 7 amps @ 17 volts with full sun. With a
controller to drop the voltage to battery level, that 7 amps will be
upped to around 9 amps. If nothing else is running, having 9 amps at
hand will allow the controller to bring the battery back to fully
charged in just a few hours, depending on how it manages charging. Good
controllers taper the current into the battery as it comes up to the
float voltage that you specify from the battery manufacturer's data
sheet. In my case, I've told my charger that 14.2 volts is the target
float voltage. As the battery voltage goes up with charge, the
controller chokes back the current until the battery is at the float
voltage. The controller then keeps the battery at this voltage with
about 0.8A charge current.
What I'm saying is that if your controller is outputting 9 amps, then
only two hours would be needed to replace the 18Ah Koolatron overnight
loss in the battery, but a good controller will not hurry things like
that -- it might stretch it out over a couple more hours. But anyway.
You should have enough sunlight and current to do the job, unless you
really hammer the battery at night, and run all your appliances during
the day so that the panel can't keep up with the charging load +
entertainment load before dark comes again.
Disclaimer: this is amateur knowledge. Dennis Haynes, Matt Roberds, and
David Etter know of what they speak.
--
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
Frank Condelli typed:
> In a message dated 16/06/2007 9:21:26 P.M. Eastern Standard Time,
> LISTSERV@GERRY.VANAGON.COM writes:
>
> Well, do the math. How much power does a coolatron require?
>
> Plug the data into the Handy Battery Demand Calculator
>
> http://www.altavistaaudio.com/Westy/Vanagon/battcalc.html
>
> and see how many ampere-hours your battery will need to supply, and from
> that you can see how much power the panels will need to stuff back into
> the battery during the sunlight hours.
>
>
>
>
>
> Yes, and yes, Now more to what I'm trying to do. Yes, as Mike said the
> solar panel must be removable from the van. Tripods or similar devices and
> extension cord is a must. Panel will be connected and angleable on the roof with
> a quick detach mechanism. You don't want to be parked in the sun to get
> your electrical charge, trust me. What I want is a large enough solar panel
> that can keep my aux battery charged while operating my Koolatron or other 12 v
> cooler while parked for EXTENDED times on the Mexican beaches I will be
> visiting next winter after the wedding. Now to the Koolatron or other 12 volt
> cooler. You need to find the one that has the largest capacity and lowest 12v
> amp draw. So far my research is showing that the Koolatron P65 Kargo Cooler,
> 20" h x 16" w x 14" d at 33 quart capacity with a 3 amp current draw as being
> the best. But - I'm still looking ! My aux battery is a group 41 Kirkland
> standard automotive battery from Costco, for cost and ease of replacement
> reasons. A charge controller as explained by Dave Etter in his previous message
> will be installed and I'm still looking for the best set up here Dave has
> some pretty good recommendations. I think the idea is to get the lowest amp
> draw cooler, calculate any other electrical requirements use, calculate the
> drain on the battery and find the size solar panel that will keep the charge up
> for the 6 hours without sunlight on those Mexican beaches. So far as I can
> determine a 120w ~ 150w solar panel should work with a 3 amp draw cooler,
> Satellite radio, standard radio, 12v cooling fans and LED lighting as the only
> current draws. So why all this for an extra fridge. Well, the OEM Dometic, is
> not large enough to handle the needs of extended stays on the isolated
> Mexican beaches. Once you get out there and set up you don't want to be moving to
> go get more Cerveza or food. I know, food can be gotten easily form fishing
> or from the Mexican vendors who frequent the beaches but still being
> realistic and having been there before you need the extra capacity of an extra
> fridge. The Dometic running on propane will keep all the beer cold and other food
> stuff go in the 12 volt cooler and will last even if the power goes out for
> a few hours at night. There will be a battery saver installed to keep the
> battery from discharging completely. I think they shut the draw off at 10.5
> volts. So this may happen infrequently depending on the draw and supply during
> the day.
>
> So.........back to my original question...........what's a "GOOD" solar
> panel ? I have seen so many and so many different prices, I'm confused ! I
> was told by one salesman the difference in price of the same watt panels is
> due to the quality of the chips. He said there are first, second and third
> quality chips on the market and therefore the cheaper panels are using the
> lesser quality chips and may fail sooner. Anyone know about this ? I have seen
> 120w ~ 150w panels from $500 to $3000, so what's that all about. I see
> Canadian Tire has a 120w on sale this week for $935 and RONA has a 130w on sale
> for $1225. Anyone know about these ? My question is where is the best panel
> for the least money ! ? ! ?
>
> Cheers,
>
> Frank Condelli
> Almonte, Ontario, Canada
> '87 Westy, '90 Carat, '87 Wolfsburg (Forsale) & Lionel Trains (_Collection
> for sale_ (http://members.aol.com/Fkc43/trainsal.htm) )
> _Frank Condelli & Associates_ (http://members.aol.com/Fkc43/busindex.html)
> - Vanagon/Vanagon Westfalia Service in the Ottawa Valley
> _Vanagon Stainless Steel Exhaust Systems_
> (http://members.aol.com/Fkc43/stebro.htm)
> _BusFusion_ (http://members.aol.com/BusFusion/bfhome.htm) a VW Camper
> camping event, Almonte, ON, June 07 ~ 10, 2007
>
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