LiIon bare cell experience

Seeing that there seems to be a lot of experimenting with LiIon cells, I thought I would share today's experience with you.

I opened up an old laptop battery. Out of the 10 cells in the pack only 2 showed any voltage, all the rest showed 0.0v. Their internal fuse must have fused.

The 2 good ones I charged up using a homemade charger. I then took one of them and ran it direclty into a high flux led. The LED drew about 500ma and I monitored the battery voltage from about 4 to about 3.6v over a 10 minute period.

As I removed the tester to check the current again, I heard a small pop, the LED went out and the battery showed 0 volts.
It's possible that I may have moved some wires and caused a short. I guess the internal fuse in this cell also went open circuit.
I dont think it was the high current draw that caused the trip.

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Streak said:
Seeing that there seems to be a lot of experimenting with LiIon cells, I thought I would share today's experience with you.

I opened up an old laptop battery. Out of the 10 cells in the pack only 2 showed any voltage, all the rest showed 0.0v. Their internal fuse must have fused.

The 2 good ones I charged up using a homemade charger. I then took one of them and ran it direclty into a high flux led. The LED drew about 500ma and I monitored the battery voltage from about 4 to about 3.6v over a 10 minute period.

As I removed the tester to check the current again, I heard a small pop, the LED went out and the battery showed 0 volts.
It's possible that I may have moved some wires and caused a short. I guess the internal fuse in this cell also went open circuit.
I dont think it was the high current draw that caused the trip.

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I am not sure that I am correctly visualizing your test setup, but are you sure that "small pop" wasn't the LED failing as a dead short thus pulling the battery terminal voltage down to zero?

No, the LED is fine. Since the pop, the battery out of circuit shows 0 volts.

In any way, your battery should be able to supply at least 10Amps of current. It's quite amazing to hear that you said it poped. Have you try charging the rest of the 0.0v, you might want to check out their resistance to confirm that the fuse is blown?

Thye old motorola nicd battery have a short circuit resettable fuse in them. I think that they are the same function. Why not just use the bare cells without the circuit board? If you slow charge them or get a smart charger there should be no proble. Just be careful not to short them as they can discharge a lot of amps causing them to heat up and explode.

The cell I used was a Panasonic 18650HM with no external circuit board.
My experience with the other dead cells is once they measure 0.0v they have gone open circuit and will not accept any charge at all. The one that went pop is showing the same signs.
I will try out another cell today and see how it goes.

you have to get a camcorder li-on charger to charge li-on bare cell battery,if you use ni-cd charger you will destroy the life of the li-on battery (it happen to me once).

I have built the circuit at http://www.shdesigns.org/lionchg.html
which has worked well to charge the bare cells. The circuit id fairly primitive but it does the job.

I am waiting for some samples of IC charge controllers which will make a better charger.

The ROHM BA3170 is non SMD controller which will handle two LiIon cells. Sounds like a good opton.