I live on a river and built a campsite on an island across from my house (the dog loves it). I bought a deep-cycle marine battery but am getting too old to lug it in and out of the canoe for charging. So I got this little panel and, so far, have not run out of juice. And it's cheap enough so if someone steals it it's no big tragedy. I run a laptop, TV, fluorescent light and charge my cell phone. I even have a 12v car-vac to clean the sand out of the tent.
Of course, I'm not there 95% of the time so 5 watts is probably adequate. And I don't have to worry about overcharging. I screwed it to a big log in pretty open sun. So far, it has survived, even some small hail.
BTW, I use the power cord from an old vacuum cleaner and a 4-way 12v splitter to distribute power from the battery.
In 2006 I took a 3 week vacation out of the country. I left my car at the airport and away I went. Upon my return, I had to have the battery boosted for 15 minutes before it would turn my car's engine on. I have no idea what caused the drain (Sattelite Radio memory, car's other computers, etc), but I had to do something to prevent a $50.00 boost call in the future. A coworker told me about these devices and how his brother uses them to keep his mobile home powered when parked. Higher wattage products are sold, but if all you're doing is keeping a car battery charged, 5 watts is plenty of power for the job. No other devices (charger controllers) are needed. The charger comes with a couple of ways to hook up to the battery (direct battery terminal clips, cigarette lighter plug). I used the cigarette plug. Just plug it in to the power port, and lay the solar energy collector side face up on your dashboard. For those with heavily tinted windshields, I have no idea if the tint would cause a problem with the panel's energy collection.
This year, after returning from another 3 week trip (and using the solar charger), my battery started better than it did before my trip to the airport!
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I recently ordered one of these panels (June 2007). The first one arrived shattered the manufacturer packaging does not protect the panel much and it was inadequately packaged in the shipping box by Amazon. The replacement unit was also badly packaged for shipment.
I tested the electrical output in full sunlight and got 20V out into a 100 ohm load -> 4 watts which is pretty good.
One thing to consider though is that this product is not very rugged. The solar panel has a plastic frame but the middle is unprotected on the back (and front). So unless you handle it very carefully it is likely to break.
Someone using this on a car dashboard would need some sort of protective carrier (like those insulated pizza boxes) to protect the unit when it was not being used.
-----------Update Dec 2007 ----------------
Panel stopped producing electricity in November. Had to send it in to Sunforce at my expense for warrantee replacement. They promptly tested it and sent me a replacement. One thing I did notice is that the plastic housing on the unit that I returned had developed some small cracks. I am using the unit on my car dashboard to keep my battery charged.
-----------Update Jan 2013 ----------------
The frame around the panel has warped and cracked. As a result the panel no longer reliably charges my battery. This product isn't really engineered for reliable operation on car dashboards the plastic / frame cannot deal with the extreme temperature changes over time.
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I took this on my one month trip to the Colorado mountains and used it daily. It kept my batteries charged that I use to run my pop up, and they never did run down. After 10 days of using one I switched to another battery just because I wanted to, but the one I was using was still working fine. I wasn't using a lot of power, but at the same rate of use I've never gotten more than four days out of charged battery before without a solar charger. This works very well at a great price. I got it soaked several times with no problem. I'd recommend it highly.
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This unit has consistently performed _better_ than it is rated for. It routinely generates over 140% the rated voltage and even generates the Rated Voltage on overcast days. A *streetlight* at night caused it to generate a measurable voltage (~50% rated, as I recall). Also, it is weather/hailstone resistant. I am very pleased with the performance of this item.
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This charger works great and cheap too. Also when you get it don't throw away the little plastic bag that looks like junk ads. Its a tiny metal stripped chip that you stick on the inside of your phone under the battery to boost signal strength. It works great. I would only get 1 or 2 bars in my house, now I have full bars most of the time. Its great, just read the instructions on how to do it.
