Folding Solar Panel
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Hi All
I finally got the solar panels mentioned below so here is a report on them. The panel is 5.5x8 when folded and has 5 sections 4 of which have solar cells. There are 4 metal grommets in the corners of the end panels for mounting with rope or bungee cords. It comes with a 10ft cord that can be removed and a cigarette lighter socket adapter. The panel is housed in a nylon fabric and is simi-flexiable. I measured the output at 20 volts open circuit and 380mA in noon sun. This is over 5 watts and the sun is not as bright this time of year so it should do even better in the summer when the sun is higher overhead. I connected it to one of my low power controllers and a 2.8 amp gel cell battery and it had the controller cycling within a few minutes although the battery was not really discharged much. The bottom line is this would make a great panel for backpackers as it folds up into a small package and is only a few ounces. It is much more practical and lighter than a VW panel as well as more powerful. It can charge a small gel cell or a 10 cell pack of NiMH batteries to run a K1 or KX1 in addition it could also charge a cell phone, GPS, IPod or lamp as long as you monitored the charge time. With one of my low power controllers and a small 1-3 amp hour gel cell you could leave the battery on charge all day without worry of overcharging. Don Brown >>>>>>>>> Hi All I just ordered 2 solar panels from Northerntool.com to experiment with. These panels are on close out and are rated at 5 watts. They appear to be about 4x5 when folded and fold out into 5 sections. It has a weather proof nylon shell with grommets at the corners for mounting. This looks like a great little panel for backpacking or other portable use. They are only $35 on sale now catalog number 339974-1615. I have seen similar panels go for much more than this and these are higher power than the popular VW panels. A small 2-5 amp gel cell and one of my low power solar controllers would be great for a K1 or KX1. You can also easily charge a 10 cell 2000-2500 mAH NiMH battery pack without a controller as long as you did not leave them on charge too long, about 4-5 hours with full sun. Usual disclaimers no connection with Northern Tool Don Brown KD5NDB <<<<<<<<<<< _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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G'day folks,
| nylon fabric and is simi-flexiable. I measured the output at 20 volts open | circuit and 380mA in noon sun. This is over 5 watts and the sun is not as | bright this time of year so it should do even better in the summer when the | sun is higher overhead. Calculating the wattage of solar panels by using the open circuit voltage and short circuit current does not represent a real world operating condition, albeit a common method used by manufacturers to mug the unwary. >From bitter experience (hill top solar powered microwave telephone network repeaters) I reached the conclusion that once you have got the nominal solar panel/system voltage matched all you are interested in is current into and out of the battery. Batteries operate in a world of current, Ah capacity, watts are virtually meaningless, only giving a rough guide to panel dimensioning for a given load. Regards, Mike VP8NO _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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Hi
I use 14 volts times the current delivered to calculate the wattage of a panel. The open circuit voltage is only useful to get an idea of how much overhead you have and is determined by the number of cells in series. Each cell will produce about .5 volts at a current determined by the size of the cell and the amount of light falling on the cell. This folding panel has 40 cells that are 1 1/4x 1 3/4 each. I measured 380 mA into a fully charged battery at 14 volts. .38 times 14 volts is 5.32 watts. This is what I based my statement of an output exceeding 5 watts. I have panels that output as low as 18 volts and some as high as 30 volts open circuit but as solar panels are constant current devices the open circuit voltage is really not critical as long as it is somewhat over the batteries maximum terminal voltage plus any circuit drops in the wiring or controller. My controllers use power fets with very low on resistance and shottkey blocking diodes so the drop is less than 2 volts at full rated power. I would prefer the panels were rated in current but that is not the case. Most of them are rated in watts and I have found that using 14 volts (assuming a 12 volt system) as the charging voltage gets you fairly close to the rated current the panel can produce in typical situations. This allows you to at least compare panels from different sources as well as give you an idea of what your charging current will be before you spend money on a panel. Don Brown KD5NDB ----- Original Message ----- From: "Mike Harris" <[hidden email]> To: "Elecraft" <[hidden email]> Sent: Friday, January 06, 2006 4:40 PM Subject: Re: [Elecraft] Folding Solar Panel > G'day folks, > >SNIP > Calculating the wattage of solar panels by using the open circuit voltage > and short circuit current does not represent a real world operating > condition, albeit a common method used by manufacturers to mug the unwary. > >From bitter experience (hill top solar powered microwave telephone > >network > repeaters) I reached the conclusion that once you have got the nominal > solar panel/system voltage matched all you are interested in is current > into and out of the battery. Batteries operate in a world of current, Ah > capacity, watts are virtually meaningless, only giving a rough guide to > panel dimensioning for a given load. > > Regards, > > Mike VP8NO > Elecraft mailing list Post to: [hidden email] 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 |
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