Reviving lawn light solar cells.

Hello All,

I have several solar cells from old dead lawn/driveway lights.  Ultimately, I'm sure that it was the rechargeable battery that failed, but the solar cells are in some sorry shape, also.

While they have not been tested outside in bright sunlight, in my workshop, shining a high lumen flashlight (unsure of exact output, but it does reflect significant heat to the lighted area) produced less than 600mV.  The rechargeable battery is AA size (1.5 V).

The cell faces have heavy oxidation, which is going to block light, I know.  The cell faces are encased in some sort of clear epoxy/resin substance.  The connections are badly corroded, rust is evident around cell connections (which I found strange, but perhaps it dripped down from housing screws).  I know that the connections can be replaced somewhat easily, but what about the oxidation?  Without knowing what material is is encased in, how should I proceed in removing oxidation?

No flashlight can compare to the sun, I know this.  But even without a true solar test, I know that these cells will not experience optimal performance. 

What can be done to revive these cells?

Thank you in advance for any suggestions!!  You all help me learn!

Huck

Comments

[knife141]

Semichrome metal polish is very good for removing oxidation and light scratches from plastic. I've used it on solar cells and on PDA touch screens with great success. Put a dab on a clean rag, rub it on aggressively, and buff with a clean cloth. Automotive headlight restorer will also work, but it only comes in a kit which would probably be enough for 10,000 solar cells. Semichrome comes in a small tube.

[Jack A Lopez]

There is a certain irony here, in that your plastic solar yard lights are being destroyed by the very sunlight which gives them life.

It makes you wonder:  If the darned things were intended to be used outdoors, why were they built out of materials that degrade in sunlight? 

The answer to this question is that your solar yard light was not intended to last forever. More likely, it was designed to have a very short lifetime, with the expectation that when it does die after just a few years, that you, being a good consumer-zombie, will simply go back to the store and buy another one.  Ha!

But for some reason you feel cheated, and like Roy Batty, you WANT MORE LIFE!!!  For your solar yard lights that is.

I have often wondered if there might be some way to "harden" solar yard lights to protect them the most damaging component of sunlight; i.e. the high energy UV radiation.  It might be as simple as housing them inside a glass jar, although I have not tried this.

As far as fixing sun-damaged plastic... this sounds tricky to me, but I have seen some chatter on that subject, here:

http://www.ehow.com/how_8486195_repair-solar-cell-plastic-light.html
http://www.ehow.com/how_8035126_clean-fix-solar-light-cell.html

[psychowoman]

The glass jar idea is an awesome idea seeing how when people make solar panels, they house them under a piece of glass to protect them and they don't oxidate the way that the patio lights do... I found your question looking for ways to reuse the old patio lights that have stopped functioning myself... Thanks for answering the question as to why they stopped working in the first place. I may try to fix them now that I know...

[huck alexander]

Thank you for the wonderful explanation of why this happens. These things go on blowout sales for 4 or 5 bucks. Not a terrible expense to replace a few. You're spot on about this being their exact intention. After taking a very close look, they were obviously designed (1) as cheaply as possible (2) to fail after a certain time of outdoor use, or (3) both. Not difficult to nail it down.

In order to find redemption for this trickery, I must find a way to revive them.

Slow wireless right now, so can't reply to every suggestion individually, BUT:

knife141: great suggestion. I looked up a few promising applications. And I can get "enough" for 7 bucks.

mpilchfamily: also a good option. Though I have never actually used these kits, I have seen the commercials (and the kits in the store). Part of the reason I wanted to do this was to (hopefully) reclaim the cells, but not have to fork over the dough to replace them. Though I wouldn't mind having these items laying around the shop, it's out of budget right now. I have to justify any cost to my wife, who does not understand going through the trouble when you can just buy new ones cheap. Thanks for mentioning it.

tstupple: almost exactly what I had in mind. A nice small case that folded open to reveal the panels all on one side or something. I want it to not look like I have my phone (!!or my calculator!!) wired to a conspicuous box with exposed components. I've read about people going to jail for far less. A switch, charging indicator led, voltage regulator and resistor should be encolsed and hidden. Anyone know if a tight space would cause too much heat build-up with 4x~1.8V (optimal) cells in series to the vreg?

[mpilchfamily]

You can try buffing out the coating on the cells to take out any yellowing and scratch in them. You can get a buffing kit made fore car headlights that is made by 3M that works great. Comes with all the sandpaper and buffing wheels you need to do the job with a cordless drill.
http://www.amazon.com/3M-39008-Headlight-Restoration-System/dp/B001AIZ5HY

The oxidation can be cleaned up with a small wire brush. Reheating all the solder joint with a soldering iron will also help remove the oxidation.

[tstupple]

You can wire a couple together to make a solar phone charger. All you need is 4 solar cells and a female USB plug. you need to wire 2 solar cells in parallel and 2 in series then connect to the 2 power cables on the USB plug