I've seen some rechargeable AA and AAA batteries at the store in packages labled "Solar Light" batteries. I guess they're meant for those solar powered lights you can stick in the ground along sidewalks and walkways. But why are they labeled that way? The look exactly like any other AA or AAA battery. So why are they labeled specifically for Solar Lights? How are they different from any other rechargeable? BTW, they are NiMH.
Solar light rechargables. What's the difference?
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They tend to be much lower capacity and should be cheaper.
Some theories that being able to fully charge the battery make it last longer, but it is questionable how much the capacity of a NiMh battery really declines when not fully charged. They can develop a voltage step (different from the capacity loss in NiCd), but this is recoverable. The capacity (maH) does not increase, but they develop a lower output voltage.
It is best that they do fully charge at least every once in a while. Hence, you could be okay with a higher capacity cells if you live in a sunny climate. In a poor sun climate, that could be an issue.
Some theories that being able to fully charge the battery make it last longer, but it is questionable how much the capacity of a NiMh battery really declines when not fully charged. They can develop a voltage step (different from the capacity loss in NiCd), but this is recoverable. The capacity (maH) does not increase, but they develop a lower output voltage.
It is best that they do fully charge at least every once in a while. Hence, you could be okay with a higher capacity cells if you live in a sunny climate. In a poor sun climate, that could be an issue.
RetroTechie
Flashlight Enthusiast
Perhaps a more likely explanation is that these cells may be designed to withstand overcharging better.
Especially in cheap solar lights, charging circuits will be minimal. Basically solar current -> battery with as little as possible in between. Meaning that if the LED(s) don't fully drain the cell(s) in a single night, cells will be overcharged. The alternative is to increase LED power, meaning they don't last through the night (especially in sub-optimal lighting conditions or winter time). And depending on solar cell and batteries used, perhaps overcharging can occur anyway.
Overcharging a NiMH may produce hydrogen + oxygen gas in the cell (see Wikipedia for example). From what I've read, NiMH's include materials to recombine those gasses into water (+heat!). Including more of those materials/structures may improve the ability to deal with overcharging, at the cost of capacity. It seems logical that for a solar/LED garden light, that trade-off would be made.
Especially in cheap solar lights, charging circuits will be minimal. Basically solar current -> battery with as little as possible in between. Meaning that if the LED(s) don't fully drain the cell(s) in a single night, cells will be overcharged. The alternative is to increase LED power, meaning they don't last through the night (especially in sub-optimal lighting conditions or winter time). And depending on solar cell and batteries used, perhaps overcharging can occur anyway.
Overcharging a NiMH may produce hydrogen + oxygen gas in the cell (see Wikipedia for example). From what I've read, NiMH's include materials to recombine those gasses into water (+heat!). Including more of those materials/structures may improve the ability to deal with overcharging, at the cost of capacity. It seems logical that for a solar/LED garden light, that trade-off would be made.
daan_deurloo
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I have some Batteries that came from a solar light ( Generic light green labeled 400mah NiMh, well come off at around 600+maH when charged ). Also have 800maH cells and those are in the 1000maH Range.
Yes those Generic Greenies are so cheap and you can get them from China ( Wish/Geek )
It are these batteries. They are extremely light, but works perfectly when the cell doesn't heat up so fast during charging and hold atleast 300~400mah.
Yes those Generic Greenies are so cheap and you can get them from China ( Wish/Geek )
It are these batteries. They are extremely light, but works perfectly when the cell doesn't heat up so fast during charging and hold atleast 300~400mah.
While it's a good theory, I think you will find in practice, that this is just not the case.
Pretty much all NiMh batteries can withstand a level of overcharge almost indefinitely as long as the current is not too high, and those solar panels on those lights generally have pretty low current output and as well, they only reach peak current for a small portion of the day as well ... and perhaps not even every day.
If I replace a 900mAH "solar" NiMh with a 2000-2500mAH regular NiMh, that capacity increase on its own is going to make it less susceptible in a given installation to over-charge damage, especially given the low current of the solar panels.
Those "solar" NiMh are just low capacity and cheap .... at least for the retailer. For the consumer, likely not as much. Unpackaged cells, 800mAH, will be <$0.20 for the retailer/MFR.
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When I was looking at them at Menards, they are normally 5.99 for a package of 4, but they recently had a rebate offer where you could get 10 packages for free after rebate. I just picked up 1 pack of AAA since I didn't have any AAA rechargables. I already have 4 AA, which is enough for my purposes.
