Do NOT buy hand-crank lights with LiIon cells in them!

I bought a hand-crank flashlight with three 5mm LEDs and a small LiIon cell inside. I liked it as all NiMH based hand-crank lights have terribly high self-discharge rates, and a LiIon cell would solve that problem.
I opened it up and found out it was a LIR2032 button cell.

There is, however, suspiciously little circuitry inside:



This made me uneasy, as I know LiIon cells really don't like being charged at more than 4.2V, and that cheap motor working as a generator has a widely variable output.
Then again, I thought maybe there was something under the board for voltage limiting.
As a test I hooked two multimeter leads to the battery terminals, cranked enthusiastically, and sure enough the voltage got to 4.4V!

I'd be surprised if the poor cell in this flashlight lasted more than a few months, maybe even weeks.

I'm taking the LiIon out and swapping in three NiCD rechargeable AAAs.

Now, it's not fair to say that ALL hand-crank lights with LiIon cells in them are like this. Some might have actual charging circuitry built-in. However, unless you are SURE they do, you're probably better off with the old-fashioned NiMH ones.

So crank slower.

Took it apart, and there's considerable componentry on the back of the board.
However, half of it is unpopulated. There are pads for a small IC too. I don't know if the absent components are meant to support other modes or to allow proper charging.



Oh well.

I have always recommended against most crank lights, except for Freeplay. It's far too easy to over charge, or over discharge those little LIR2032 cells, thus killing the light. A few of them don't even charge an LIR2032, they just run off a CR2032, and you are left with a light that won't work after that runs out.

Marduke said:

I have always recommended against most crank lights, except for Freeplay. It's far too easy to over charge, or over discharge those little LIR2032 cells, thus killing the light. A few of them don't even charge an LIR2032, they just run off a CR2032, and you are left with a light that won't work after that runs out.

Click to expand...

How big a does an LIR2032 make?

AndyTiedye said:

How big a does an LIR2032 make?

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Pretty sure they just die quietly, but I don't want to test it.

:thinking: um guys, that's just a 2032 Lithium battery, not a Lithium Ion battery.

The 2032 is a non-rechargeable, one time discharge, disposable battery, not unlike an Energizer E2 Lithium battery.

I'm pretty sure that's a discharge only battery and was never made to be charged. So I'm not sure what the light is supposed to be using as a capacitor. Anyhow, I could be wrong but I'll know that I'll be rightly corrected if I am..

CR2032 is non-rechargable. LIR2032 is a Li-Ion rechargable version, hence LIR = Lithium Ion Rechargable

They are rechargeable, most of those lights are (how ever pathetic the cell is), but due to the circuit design they can't hold a charge, most flashlights mechanically open the circuit, when there is no mechanical switch disconnecting the battery from the circuit it will leak power, over a few days .5mA from those cells will drain them. Hope that helps.

Wouldn't it make more sense to put in a big capacitor, probably cost the same.

The NiMH lights are pretty handy. I've got two around, and while the tiny cells have rather high self-discharge a few seconds of cranking every now and then keeps them charged enough to be useful.
I'll soon mod the best one with Jeleds and Eneloop AAAs :devil:

Fallingwater said:

The NiMH lights are pretty handy. I've got two around, and while the tiny cells have rather high self-discharge a few seconds of cranking every now and then keeps them charged enough to be useful.
I'll soon mod the best one with Jeleds and Eneloop AAAs :devil:

Click to expand...

Freeplay uses NiMH AA's. Thinking of replacing mine with Rayovac Hybrids.

Yes, a NiMH Freeplay with Eneloops upgrade would be ideal. Minimal self-discharge!

wow, I didnt expect that much SMT components on the PCB....
4.4V....mmm, is that a constant regardless of rpm?
if thats the case extract it and mod it to run of a bicycle

AndyTiedye said:

How big a does an LIR2032 make?

Click to expand...

firecracker equivalent...probably not the best thing to do
I've tossed Cr2016s into fire before, Im fairly certain LIR2032s might pop louder

double post

Illum_the_nation said:

wow, I didnt expect that much SMT components on the PCB

Click to expand...

Me neither.
I wonder what they do, since they're obviously not doing anything related to charging. The light has two modes (one led / three leds), but you'd think a three-stage switch would be enough for that...

4.4V....mmm, is that a constant regardless of rpm?

Click to expand...

No, just if you crank it fast.
Problem is, if you crank it too slow it doesn't get to a sufficient voltage and doesn't charge at all.
This means that the cranking speed has to be kept in a not-well-defined narrow range to allow charge and prevent overcharge.

The LIR2032 has been removed and used for another project of mine. When I get the Jeleds I'll do the mod.