I just recieved my VW solar panels and have a question.

[Alphacarina]

I just measured my single VW panel output and got the following:

14.05 volts
0.24 amps

And its a beautiful sunny day. Thats about 3.4 watts. Not as good as I would have hoped but good enough

Assuming you're charging anything larger than a motorcycle battery, you'll have no need of a regulator then - No way you can overcharge even a garden tractor battery with a 1/4 amp panel . . . . even if the sun shines 24 hours a day

Don

[Airspeed]

I have 4 of the same panel and I removed the in line charge controller that came with them and they measured 23.5 volts, how will the higher voltage affect the wattage?
Thanks! Aaron

[bdosborn]

How did you wire them together? Did you wire them with all the red wires connected together (parallel) or red to black (series)? I don't think you want to charge with a voltage that high. But, I think your Siemens controller will regulate the voltage down to a more acceptable level. What's the voltage with the controller?
Bruce

[Airspeed]

I wired them in parallel, but the panels measure 23.5 volts individualy as well. The Siemens controller can handle up to 26 volts so I should be ok.
Im just curious how the higher voltage affects the wattage?
Thanks! Aaron

[bdosborn]

It shouldn't affect the wattage, that's a function of the device and won't be changed by a higher voltage. The current the array puts out will go down though. 20W/23.5V=0.85A. The voltage might fall when you put a load on the array. Have you wired it to your battery yet to see if it goes down?
Bruce

[Airspeed]

I haven't wired it up to the charge system yet, I am going to wire up the controller and a new fuse block this evening when it cools off a bit, My tear is sitting in full sun and I feel to lazy today to drag it in to the shade. unfortunately the sun will be going down by then so I will have to wait until tomorrow to see the results. I did hook up a 12 volt light to one of the panels a little while ago, the bulb burned brightly for about 5 seconds then "Poof" the bulb blew. I will post the results of my charge system tomorrow when the sun comes up. Thanks again! Aaron

[Alphacarina]

Unloaded solar panels sitting in the sun will give you some really ridiculous voltages - They don't mean a thing. As soon as you connect the panels to even a small load, that voltage will come down into the correct voltage range - Something around 14 volts

Wattage is the volts times the amps the panel can produce in full sun, under a load - Usually it's a little lower than the spec'ed wattage for the panel, because those are 'cold' numbers and as soon as you begin to 'work' the panel, it will heat up some and the wattage will go down a little

I 'lived with' a pair of 100 watt panels permanently mounted on a hard bimini on my 34' sailboat, connected to a pair of 400 AH battery banks, powering a 12 volt refrigerator - I never used a voltage regulator because the panels couldn't put out more power in 24 hours than the fridge consumed, so no danger of overcharging the huge battery banks. I could anchor in one spot for a couple weeks though and run the fridge, the stereo and TV and all the lights before I needed to run the diesel engine to recharge the batteries though - Since I seldom stayed put in any one place for longer than a week or so, the panels saved me lots of engine running time and therefore, lots of $$$

Don