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