Hi There may be two different types out there or you may not have them in the same intensity light. A Solar panel is a constant current generator. Its current and open circuit voltage is dependent on the amount of light falling on the panel. Each cell in the panel outputs about .5 volt in full sun. The cells are connected in series or series-parallel to get the voltage high enough to charge the battery plus a little overhead. The VW panels only need about 14 volts to charge the battery in the car so they may have a version of the panel wired for only 15 volts. The three panels I once had would output about 18 volts in full sun open circuit and about 170 mA under full load. You can test the output current by connecting a 10 ohm 5 watt resistor across the panel and measuring the output voltage. 170 mA would be 1.7 volts. I have some commercial Solarex panels that will output up to 30 volts open circuit in full sun and almost 6 amps under load. This panel is about 20x57 and rated at 80 watts. The VW panels have a blocking diode in the plug to prevent reverse current. This reverse current will discharge the battery when the panel is dark. If you remove the plug be sure to install a blocking diode unless your controller includes one internally. You can parallel several panels to increase the current but a blocking diode is a good idea on each panel to prevent reverse current flow when one panel is in the sun and another is in the shade. Even if you have two panels with different voltages if you parallel them through the blocking diodes once they are connected to a load the voltage will drop to the battery voltage and the current from each panel should flow into the battery.
Don Brown KD5NDB ----- Original Message ----- From: "Scott" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Tuesday, June 21, 2005 6:48 PM Subject: Re: [Elecraft] Using the KX1 on Solar Power > Don Brown mentioned the VW solar panels... > > After seeing them referenced on this list a few times over the years, I > finally went to the local dealer yesterday, asked gently about solar > panels, > and walked away with two of them. What a deal! > > ( Now I'm wondering: Why does one read 15V and the other 25V when they're > side by side? ) > > Scott N1AIA > K1 00139 > > _______________________________________________ > Elecraft mailing list > Post to: [email protected] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
