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garden lanterns' solar panel help needed

hafcanadian

I'm new to learning circuitry, so forgive any ignorance that I may reveal

 

I've got several solar yard lanterns of various sizes that I've accumulated over the last 10-15 years.  Some are classical, some have an amber glow, some "flicker" like a candle, and some are modern with bright white LED's that have little staying power and dim within a few hours after nightfall.  Out of about 10 of them, only 4 still function, and two of those have to have their AA batteries recharged manually in order to work.  Some of the others might work if charged batteries were inserted, but I haven't tried them all;  running around the yard each evening removing dead batteries and installing fresh Nicads or Nihydrides just isn't plausible.

 

Lately the oldest lantern, heretofore very reliable, has started failing as well, so every several days I replace its rechargeables with fresh ones charged in the house.  In all cases I can see the solar collection panel on the top (some newer lanterns have 4 panels) has deteriorated.  The surface of the panels loose their smoothness and polished shine, but below the surface the visible pathways have dimmed and discolored.  The oldest (and most favorite) has worked flawlessly for 10 years or more until now, whereas others I've bought lasted only a few months before summer sun faded their panels to an inoperative state.  The manufacturer sent replacements that have lasted several years, but one of those is acting up this season, and they never asked for the 2 original lanterns back so I still have them.

 

I'd like to replace the faded and faulty panels and get as many yard lanterns up and running again as possible.  It's obvious that in almost all instances the problem comes from failed or failing solar panels, although some circuit boards aren't in the best condition;  they are outside afterall, exposed to moisture and spider activity.  The lanterns were made by various companies, some of which no longer exist, and all of whom will not replace panels.  They are bulk-made in China - the market has no room for parts provision as a customer service.

 

Can anyone advise me on a source for replacing the various types and formats of small garden lantern solar panels?  I'm sure there will have to be some consideration for electrical output capacity as well as physical size, but I should be able to get that information for each lantern off its battery pack, circuit board, or instruction sheet if I still have it.  I'm still unclear as to whether I'll need to be careful which battery type to use - the oldest ones use Ni-Cads, the newest ones use NiMh;  I know I have to use the proper charger for each in the house, but can the older lanterns charge NiMH?  Ni-Cads are getting hard to find in stores anyway.  I need resources for obtaining decent panels though.  From the two units that faded and failed within a couple of months in the sun, I can tell there's junk or poorly coated panels out there I need to avoid.

 

Thanks for any help.

-hafcanadian

  • 0

    Generally it is hard to suggest replacements that are not identical, because it is guesswork what the original designer intended. For example NiCd cells have a different end-of-charge detection than NiMH (NiMH has a different voltage gradient preceding charge termination, from memory, and for NiCd various designers may use different methods, such as change in voltage, or temperature gradient, or combination). Without a circuit diagram (which only the manufacturer is likely to have) it is not easy to know. A simple garden device might just trickle charge however - it's the most likely scenario. It's safer and more likely to work for another 10 years if replaced with similar cells, i.e. NiCd and not NiMH.

    Farnell do sell solar panels, however they may be too large. This leaves you with scouring hobby electronics sites or ebay unfortunately, for something approximately the same size so it can fit. In theory solar cells should last for 20 years or more if assembled well. 10 years is quite good for a garden lamp. There are a few different types of solar cells, some more efficient, but it may come down to cost.

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    Hi Joel  I have taken several different kinds of lawn lamps apart and looked at the circuits. In all cases it is a 2 volt solar panel that feeds through a voltage sensitive solid state switch. When the voltage from the solar cell is sufficient it trickle charges the battery ( one AA or one AAA ) and when the voltage from the solar cell falls below a certain level it switches the battery over to the LED. I do not believe it will matter if it is a NiCad or a NiMh cell as no charging control is incorporated in the circuit. For the fun of it you might try buffing the surface of the solar cells to make them smooth and clear again. If I was going to try this I would use some automotive paint polishing compound. If you have a small multimeter you could check the current that is flowing from the solar cell to charge the battery before and after polishing. This would tell if it is improving the charge rate or not. I recently bought, for parts, some yard lamps at the Dollar Tree store for $1 a piece. Each one has a solar cell, an LED, a switching circuit, and a AAA rechargeable battery. Not a bad deal for a buck. I have some old dull photo cells from some old awn lamps and tomorrow I am going to try to polish then to see if I can improve their output. I will let you know the outcome.

    John

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    Hi Joel, I ran the experiment. My old solar cells weren't as bad as I remembered. I tested them under load with a constant light source before polishing. After polishing I could see a visible difference in the clarity of their surfaces however it did not affect their output. You can try and it might make a small difference if the cell has a very dirty of cloudy surface but it may not be as effective as I hoped for.

    John

  • 0 in reply to jw0752

    I tried using a 2-part plastic polishing routine last summer on several of the lanterns.  It did improve some a bit, but then there are those that aren't working at all.  I'd just like to replace the discolored panels altogether in the hope that there are better quality ones out there;  I presume that means they have finish coatings on them that protect the inner circuit from deterioration.

     

    It's pretty obvious, from the two big ones I bought a few years ago where the panels all (4 per light) totally "fogged" over within a couple months use in the sun, that there is a big difference in panel coatings.  The two that the company sent as replacement lanterns haven't deteriorated, although one of them has turned contankerous operationally just this summer.   I've yet to take it down from its high mounting place to examine it;  could be just bugs or spiders on the circuit board.

     

    My favorite ones are the oldest - one larger white resin-bodied "pagoda" and two small version "pagodas" I think that I got at Costco about a decade or more ago.  Their lamps "flicker" like a real candle and have a natural yellowish tint as opposed to today's bright blueish LED lamps.  I have one small coach lantern style that's about 7 or 8 years old that flickers too, and it still works very well.  The two small pagodas quit on me within the last 5 years, though one still works if I recharge the batteries in the house.  Ditto for the old reliable large pagoda which just this season finally opted not to solar charge itself - it was my very first solar one and remains the most treasured.

     

    I bought a pair of stainless coach lamps 5 years back, but I'm not nuts about them.  One quit totally and the circuitry was so bad I tossed it out.  They put out a bright white light that only lasts a couple of hours after the sun goes down.  At least the remaining one does still work, such as it is.  I would like to rejuvenate the pagoda ones at least, since they are really beautiful when fully operational.  You can see cloudiness deep around the metal foil inside some panels, and some are so clouded you can't see the foil strips at all.  One panel totally came unglued from the top of one small pagoda, fell off, and is completely clouded anyway.

     

    I think the panels just need replacing but don't know where to get them.  I'll try the Farnell site as Shabaz mentioned, but won't hold my breath.  As he alluded, my lamps have different size panels in different configurations from one alone to four in groups, and from 2"X2" to maybe 1"X3".

     

    Joel

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    Hi Joel,  If you are going to try to order replacement cells from someplace other than a manufacturer you have to be aware that the solar cells used on these lights are not single cells but rather 4 cells built into one package. A single cell has only 1/2 volt and would not be able to recharge a battery. Therefore they get special packages with 4 integrated, in series, solar cells that put out 2.0 volts. This give them enough voltage to get through the internal switching circuit and still have enough voltage to charge the battery.

    John

  • 0 in reply to jw0752

    Wouldn't ya know I'd find them readily at Amazon.  Since all my lanterns use AA rechargeables, either NiCd or NiMH, I'd assume one of these 3v units would do, at least for the smaller pagodas;  the original panels look a lot like these

    Amazon.com: Small Solar Panel 3.0V 70mA with wires: Industrial & Scientific

     

    Others at Amazon are options perhaps for the other lanterns.  I just am not sure how resilient and long lasting they are, except for whatever reviewers' information on each item there may be.

     

    JOel

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    Yes those look like they will work just fine if they have the right physical size. They in fact look just like the ones I was using in my test.