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My solar-powered driveway lights are a nice, cheap, science project

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embeddedrocks
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re: My solar-powered driveway lights are a nice, cheap, science project
embeddedrocks   8/19/2010 2:20:31 PM
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I purchased units with a glass top on an anodized or powercoated aluminum head. They had a Westinghouse brand name, and cost $2.50 each from Walmart. I initially purchased 6 last Spring and added 4 more. I certainly could not assemble them myself for three times that cost. The finish on the initial six is fading, but they still run 5-8+ hours per night depending on daytime sun, and did so all Winter when they were not buried in snow. It was remarkable to me that in our harsh upstate NY winters, they would exist under the snow for a week or more until uncovered by wind, then begin to function again. They also functioned quite well at -8 deg F, as well as our August heat (90+ Deg F ambient - though these units were much hotter from the solar radiation). The weather sealing is effective on these. Let's see if they survive two Winters. The battery is replaceable, so I intend to keep them running. I enjoy the light too much to bring them in for the Winter. To my children it is a simple but effective demonstration every night of how we can harness the sun's energy, store it, and use it when we need it.

Craig.Force
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re: My solar-powered driveway lights are a nice, cheap, science project
Craig.Force   8/16/2010 9:41:31 PM
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On a related note; I've run a solar powered dc brushless bird bath fountain pump in my TX backyard for over three years. Despite 100+ degree temps days running have left it to run dry many times it still works like a champ. The pump is low quality from China. If you're in the market for an integrated bird bath / solar cell and fountain pump, be sure to get one with a glass covered panel. Early models used a soft plastic panel encasing the cell which become hopelessly calcified from filling with city tap water from the hose bib (manufacturer recommended filling with distilled water...not in my backyard).

Raymond.Rogers_#1
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re: My solar-powered driveway lights are a nice, cheap, science project
Raymond.Rogers_#1   8/14/2010 12:53:18 AM
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"Of course, all of the units have a short run-time, usually less than an hour, and all of them come on befor it is really dark" Judging from the pr4403 circuit the threshold is set to high. In addition my NiMh units lasted over 6 hours, and even my off the shelf unit from last year with standard NiCad batteries runs for over 4 hours. Over all you seem to have poor units. Trying to NiMh batteries might help since the charge and discharge curves are flatter; but I doubt it. You could always reuse the batteries in a camera if they didn't help.

Rocketman49
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re: My solar-powered driveway lights are a nice, cheap, science project
Rocketman49   8/13/2010 11:27:27 PM
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I’ve been running experiments on my solar powered lights the past 4 years. I found, like Raymond, that NiMH batteries were compatible with the inexpensive NiCd charging circuits. The higher cost of the NiMH batteries is overridden by the longer life (2X) and better discharge characteristics over NiCd batteries. Spraying the insides with a good coating material helps with water corrosion on the contacts and PCB. It also discourages insects from making the internal spaces of your solar lights home. The solar cells from two lights that failed, after 3 years, have become part of a solar monitoring experiment.

WKetel
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re: My solar-powered driveway lights are a nice, cheap, science project
WKetel   8/13/2010 9:55:03 PM
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I given a few of these by friends who know how much I enjoy fixing things. What I have found as the most common failure mode is corrosion on the battery connections, which prevents charging and discharging. One unit also had a bad solder connection to the photocell array. Of course, all of the units have a short run-time, usually less than an hour, and all of them come on befor it is really dark, so that mostly they have run down by the time they could be useful.

Ted.Keys
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re: My solar-powered driveway lights are a nice, cheap, science project
Ted.Keys   8/13/2010 7:52:12 PM
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I've had a few of these. The usual failure mode involves being thrown in multiple pieces across the yard by a weedeater that got too close.

Raymond.Rogers_#1
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re: My solar-powered driveway lights are a nice, cheap, science project
Raymond.Rogers_#1   8/13/2010 6:58:58 PM
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Some referances for NiMh usage. Titles rather than google links; because the links are rather long Trickle charge: "The Nikonians Battery Guide" says that modern NiMh will tolerate .1C trickle charge. In fact the cheap solar cells won't come close to that: .1C for 2000mah is 200 ma is completely outside of their range. IC PR4043: pr4403.pdf It doesn't get a lot simpler than that folks. Solar cells: I haven't located a good reference; but I doubt if the little cells ever deliver 200ma; but the real thing would be doing load line analysis (vi battery charging vs. cell output) and tolerancing. Oh yes; I recommend spraying the insides with some coating. The units I looked at, after a year, looked reasonable but there was a lot of stuff that could have been attacked; bugs, salt, dew, etc....

dworkman
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re: My solar-powered driveway lights are a nice, cheap, science project
dworkman   8/13/2010 6:01:11 PM
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I bought 18 of these in a pack from Sams Club a while back. real glass, stainless steel, looked like quality...what a mistake. After 1 month half of them had failed. After a year only 1 or two were still working. I have managed to resurrect some but my overall impression is that they are all produced without the slightest thought as to life, and actual testing of the product has never ocurred to them. Main problems, other than shoddy workmanship, are corrosion of the battery contacts and CdS photocell, and bad batteries.

RLohrbach
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re: My solar-powered driveway lights are a nice, cheap, science project
RLohrbach   8/13/2010 5:34:04 PM
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I appreciate the sharing and look forward to trying out some of the suggestions others have already tried. Ours were $2 ea at Walmart.

Raymond.Rogers_#1
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re: My solar-powered driveway lights are a nice, cheap, science project
Raymond.Rogers_#1   8/13/2010 2:56:56 PM
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I did check and it was actually more compatible than NiCad. I can look up the chip and circuit that was used. About as low-tech as is available these days. After all these units only have to gather energy from crude photovoltaic cells, save it, and then deliver it when the source fades. They do not meet stringent requirements. In Mexico they charged and ran for about 8 hours at night. Reasonably sunny but sometimes cloudy.

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