Solar cell rechargeable patio lights.

[HuFlungDung]

So my wife is a 'light nut' (and she never reads these forums, heh ) and somehow, she's got me checking out the ones that don't come on, etc. I guess, with my Scottish nature, I'm also unwilling to throw anything out that might be made workable Heck, I've fixed a bunch of dodgy Chinese soldering jobs and gotten lots of lights working again

So I've got this one dual AA LED lamp that goes dead after a day or two, and I check both batteries and one is good and the other is dead. I've replaced the cells, and the same thing continues to happen.

When I check the voltage output of the solar cell, it doesn't seem to be high enough to charge against two AA's so it must charge one at a time. So does it work this way, and is there some kind of switching circuit that takes care of this?

I'll bet no one on these forums knows the answer to this one

[Geof]

Originally Posted by HuFlungDung .....I'll bet no one on these forums knows the answer to this one

Are you trying to challenge people.

Obviously your Scottish blood is more Scottish than my Yorkshiremans' blood is Yorkish; I throw the damn things out when they don't work.

Which has been surprisingly rare.

[HuFlungDung]

Yes, I'm trying to challenge someone

I also like to boast to my wife, whenever we play cards or crocinole, that I'm going to whopp her and her teammate: it makes her try harder to win, and I feel really good when I do pull it off, and she feels sorry for me if I lose Ain't I a shmuck? But hey, I fix her lights!

[bharbour]

Originally Posted by HuFlungDung So I've got this one dual AA LED lamp that goes dead after a day or two, and I check both batteries and one is good and the other is dead. I've replaced the cells, and the same thing continues to happen. When I check the voltage output of the solar cell, it doesn't seem to be high enough to charge against two AA's so it must charge one at a time. So does it work this way, and is there some kind of switching circuit that takes care of this?

I have never been inside one of those lights, but I would expect that it uses a little flyback boost converter. Are there any inductors on the board? The reason I am expecting a boost converter instead of switching batteries, is I think it would take more parts to switch between batteries than a little flyback boost converter.

Is it always the same battery that is going dead? Is there anything connected to the link between the two batteries? Can you post a detailed picture of the board from both sides? This seems like an interesting puzzle.

BobH

[jmelson]

Originally Posted by HuFlungDung So my wife is a 'light nut' (and she never reads these forums, heh ) and somehow, she's got me checking out the ones that don't come on, etc. I guess, with my Scottish nature, I'm also unwilling to throw anything out that might be made workable Heck, I've fixed a bunch of dodgy Chinese soldering jobs and gotten lots of lights working again So I've got this one dual AA LED lamp that goes dead after a day or two, and I check both batteries and one is good and the other is dead. I've replaced the cells, and the same thing continues to happen. When I check the voltage output of the solar cell, it doesn't seem to be high enough to charge against two AA's so it must charge one at a time. So does it work this way, and is there some kind of switching circuit that takes care of this?

NiCd batteries have one weakness, if you ever reverse the polarity of a cell, even sometimes for just SECONDS, the cell is irreparably harmed, and will never hold a charge again. Any time a string of cells is discharged too far, the weakest cell gets reverse voltage and is trashed. This is what is happening. Now, does this have a low-charge cutoff, or does it depend on the forward voltage drop of the LED to cut off current when the cells get low? You may need to add a diode in series with the battery string to allow this cutoff to happen before the cells run down too low. Finally, if the solar cells can't get up to at least 3.6 V there will be no charging of the cells. You might be able to save it with an aluminum reflector to funnel more sun into the solar cells, but if the solar cell has deteriorated by heat and UV exposure, then your only hope is to replace the solar cells.

Jon

[lwill]

Do you have more than one light of this style?
Open another one up that is still working and compare the voltages.
Are you measuring the voltage of the solar cell with the batteries connected? Is the bad cell dragging it down?
Are the batteries in series or parallel? (brighter, higher voltage - ~2.4v, or longer run time - higher Ah)
Did you replace both cells at once? Is the one that was dead, actually bad or is the other one killing it?
If you have more than one bad light, do they all have the same problem? Can you combine them to make the wife half way happy? Use 2 worn solar cells on one light?
That is most of what I can think to check with out seeing it.
Lyle