Date: Sun, 17 Jun 2007 18:47:45 -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: <007101c7b12b$c601df30$febad34b@t41>
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Using these conservative assumptions, let's analyze my system.
Assume 6 hours of sunlight / day, with panels derated by 15%, as
suggested. My panels are 2x45W, = 90W, derated by 15% = 77W * 6 hours =
450W / day of power production. Assuming a 12.6 voltage system, call
that 35Ah of available power / day.
Our Norcold draws 2.5 amps when running, so if it ran for 24 hours a
day, it would use 2.5A x 24 = 60Ah in a day. But it doesn't run
full-time, it cycles on every ten minutes and on hot days it might run
five minutes per 10 minute cycle, and on cold nights maybe a minute per
cycle. So that's about 1.25 Ah during the day, and a lot lower at night.
So for a 24-hour period, call it 20Ah for the reefer.
We use a laptop about 2 hours a day. Laptops generally pull 3 amps. Say
we run the laptop for two hours -- that's 6Ah.
Our little Philips DVD player draws about 2.5 amps, and a film is
usually about two hours, so that's another 5Ah.
For lighting we have some 8-watt 12-volt dc fluorescent fixtures, and a
couple of 12-volt halogen "reading lights." Each of the various lights
draw an amp or so when running, but we don't do a lot of that - one
light at a time, usually, and no lighting if we're watching a DVD. For
general lighting we use Dietz oil lamps. Electrically, we probably use
less than 1Ah for lighting per night.
All told, we use around 35Ah per 24-hour period. Add 25% as suggested,
that comes to 44Ah.
Based on these numbers, we're clearly using 9Ah more energy per day than
I'm generating from my solar rig. But in real life, our battery is fully
charged by noon every day and until we lose sun in the evening, we have
a power surplus.
Now if my life depended on a solar power system, I would use very
conservative assumptions, at least as pessimistic as the ones that Larry
has proposed. But we are only camping, and in good weather, too. If
things get sucky, we'll move on.
--
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
Larry Chase typed:
> Frank,
>
> Based on my own experiences with solar, I have a couple of concerns with the
> assumptions
>
> 1) "find the size solar panel that will keep the charge up for the 6 hours
> without sunlight on those Mexican beaches."
>
> Actually just the opposite is true.
>
> For system design you should assume 6 hrs of good solar production each day.
>
>
> This is a standard solar design parameter and I have found it be be
> accurate.
>
> Whatever your total daily usage requirements are, you need to be able to
> replenish that amt in 6 hrs of solar usage.
>
> Your actual experience will be a bit better in Mexico because of the extreme
> southern location ... But 6 hrs is a good solar
> planning number.
>
>
> 2) "So far my research is showing that the Koolatron P65 Kargo Cooler, 33
> quart capacity with a 3 amp current draw as being
> the best."
>
> Koolatron's are Thermoelectric Cooler and actually are not very efficient.
>
> It is much like comparing the efficiency of our OE Dometic fridge to a newer
> Norcold DC0040 fridge.
>
> A direct valid comparison would be the Koolton P65 vs a Engel MT35
>
> The Kooltron P65 - Thermoelectric Cooler
>
> Cost ~$145
>
> - Uses 3 amps per hr on 12 volt
> - Duty cycle is approx 100 % ... runs continuously
> - Performance spec is 40°F degrees below the outside temperature. 90F
> outside will get you 50F fridge temp.
>
> So a kooltron using 3 amps per hr at 24 hrs will equal = 72 amps hrs daily
> usage.
>
> Solar panel requirement would be = 72 AH / 6 hrs = 12 amps per hr.
>
>
> The Engel MT35 - Compressor operated (Reliable & Efficient )
>
> Cost ~$690
>
> - Uses 0.7 - 2.5 Amps per hr on 12 volt. I estimate the average usage would
> be 1.5 amps per hr.
> - Duty cycle, I would estimate approx 50% at 90F outside temps. So figure 12
> hrs per day.
> - Performance spec ... Set it at any temp you want all the way down to 0F no
> matter what the outside temp.
>
> So a Engel using 1.5 amps per hr for 12 hrs per day = 18 amps hrs dailt
> usage.
>
> Solar requirement would be = 18 AH / 6 hrs = 3 amps per hr.
>
> That’s 72 amp hrs for the Kooltron vs 18 amp hrs for the Engel.
>
> Big difference.
>
> Of course the cost of each unit is significant ... $145 vs $690.
>
>
> 3) Battery automotive battery vs deep cell battery
>
> You might be able to get by with automotive battery with a Engle ... But I
> don’t thing you will using a Kooltron.
>
> If you were just using it on a weekend here and there ... A standard
> automotive battery would be fine.
>
> But you will be using it everyday and that means you will be cycling the
> batter everyday.
>
> No automotive battery will last long with that usage.
>
>
> I would made these recommendations.
>
> 1) Assume no more than 6 hrs of efficient solar production per day during
> summer.
>
> 2) Derate solar panel specs by 10-15%
>
> 3) Increase calculated estimated usage by 25%
>
> 4) Put panel in sun and van in shade
>
> 5) Keep the connection cord as short as possible (longer length = less
> efficiency)
>
> 6) Use a properly rated gauge for the connection cord
>
> 7) Go with a efficient cooler like Engle
>
> 8) Install a deep cell battery for the cooler.
>
> larry chase
> www.roadhaus.com
>
> - - -
>
>
>
> Date: Sun, 17 Jun 2007 07:20:08 EDT
> From: Frank Condelli <RAlanen@AOL.COM>
> Subject: Re: Solar panels for your Vanagon..
>
> 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
>
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