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LandLocked66c 01-28-2010 07:37 PM

Solar Panels?
Hey guys, I have some questions about this particular scenario. I've got quite a few of these VW car solar panels. They use them at dealerships to keep the cars batteries fresh. If I had 4 of these running parallel to a controller then to the battery bank, do you think it would help much? How fast would it charge? I've just started reading the 12volt Bible so be easy on me... :D

Here are the specs:

Elec. Ratings at 1000 W/m squared, AM1.5, Cell Temp. 25 degrees Celcius

Max. Power: 3.2 W
Voltage at max. power: 18.8 V
Current at max. power: 170 mA

It looks like this gentleman figured it out as well... First 235 Tips: VW Solar Panel for Battery Upkeep

Architeuthis 01-28-2010 08:02 PM

If you had 4 you could have up to 12 watts. I doubt that it would charge much at all but if your bank is small it might keep it up while in storage. It really depends on bank size and type.

Of course the advantage is no need for a regulator. I have a 30watt that is so small for my bank that I do not need a regulator for it, even in florida but then I always have something on.

LandLocked66c 01-28-2010 08:08 PM

I plan on running two 6 volt deep cell batteries in series. It's a 23' boat so all i'll be running will be depth sounder, radio, and lights at any given time. I'd like to run more like a laptop and router but that's down the road...

sailingdog 01-28-2010 09:29 PM

If you're running two T105 golf cart batteries in series... those four panels are barely going to keep up with the self-discharge rate on the batteries..

LandLocked66c 01-28-2010 09:56 PM

Holy crap! So how many would I need then to be any kind of help? I should be getting quite a few tomorrow! Maybe I could lay the whole deck with them! :D

Architeuthis 01-29-2010 12:18 PM

Even free I doubt they would be worth it as they take up too much space. Maybe get enough to keep batteries charged while away from the boat. Determine that by checking voltage every time you visit the boat (you already do that) and keep adding until you find the voltage does not drop between visits but is not higher than about 13volts, or get a regulator at that point.

COOL 01-29-2010 12:51 PM

It is definitely worth playing with.
I find my 400mA 6W panel is big enough to
work as a maintenance charger.
I also have a 1.2A 18W panel that can keep
up with our live aboard house loads in the summer.
On a very sunny day it can be powerful enough to
cook a battery if used without a charge controller
and not watched carefully.

mitiempo 01-29-2010 02:31 PM

1.2 amp keeps up with your house loads? You can't be turning much on though.

wind_magic 01-29-2010 03:06 PM

Land, those smaller panels are really better for camping and charging up things like your music player, laptop, or other personal electronics. They do a good job of that!

LandLocked66c 01-29-2010 03:49 PM

I need to research this more, but is it possible to run multiple panels in series to increase output? I know that most panels are just a bunch of cells run in series to give more output. Bigger panel means bigger output. If I end up with enough of these I may sacrafice a few for research! :D

If anything, my main goal would be to make sure my bank doesn't get 50% discharged at any given time. I don't know what my average weekend of use will consist of yet - hell I don't even have the boat in the driveway yet... :D

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