Ted YapoNot great, but something. If you count just getting them to start, it's 19, but really only 3 were properly driven.
The NiCd's were charged in about a day, so the current drain on the CR2477 was fairly high (for a coin cell), and not much energy was extracted to the NiCd's.
I have some others charged over longer periods, but I'm saving those for my #Coin Cell Jump Starter .
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After this test, I decided to see how many screws the same cells could drive if charged fully in a normal charger.
Answer: at least 27! That's all the holes I had. So, the coin cell charged the NiCd's to no more than 11%. I suspect it was less than that, though, since the screwdriver still had enough juice to remove all those screws after I stopped the video!
If I end up with some extra cells after the jump starter experiments, I might try this again.
I always thought this screwdriver was lousy, but I never tried it with anything but alkaline cells. With NiCd's, it's actually not that bad...
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Yeah, and flat charge curve, too. During charging, the NiCd voltage goes from 0 (after being shorted) to 1.2+ in a very short time, then stays there. Really no way to know what's happening by the voltage.
From what I've read, the only way to really know the state-of-charge (for both charge and discharge) is Coulomb counting: keep a running tab of the current in/out of the cell.
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@EricH NiCds still power the bargain cordless tool industry. Lithiums have taken over the high-end, but the NiCd is still used for many of the cheaper ones. They're inexpensive, easy to charge, and the constant-voltage discharge means power lasts until they're dead.
Oh, I should say that you can detect a fully-charged cell while charging by a few different mechanisms, so you can tell 100% and 0%, but in between it gets hazy.
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