How to reset Li-ion protection?

[herbicide]

Hi there.

I'm sure this vast pool of collective wisdom can help me.

I just received a pair of Ultrafire protected 17670s. Unfortunately one of them appears to have had it's protection circuit tripped, as it showed 0.00V when I took it out of the wrapper (I check all rechargeables as soon as they arrive).

My charger (WF-139) picks up the working one fine, but the one showing 0.00V just gets a green light.

I left it in the charger for a few minutes to see what happened and the voltage climbed, so it's being charged (I assume the charger has a threshold that the cell is still below, and won't pick it up.), but is it safe to continue to charge it?

I could RMA it, (I have a DX support ticket open) but would prefer to avoid the hassle and delay if at all possible.

So, am I good to proceed or not?

 

[DM51]

It's not a good sign that it arrived having been at a low voltage throughout transit, and for who knows how long before that. Li-Ion cells stored at low voltages will deteriorate.

What was the voltage after the few minutes you had it on the charger? If it was <3.0V, get rid of it.

However if it was >3.6V, you may be OK. Charge it to the full 4.20V, then let it sit for ~1 hour and measure the voltage again. If it has dropped to 4.0V, throw it out.

Ultrafire are crappy cells at the best of times, with lots of failures.

 

[herbicide]

The other cell shows 4.02V and seems OK. (I'm still waiting for a 1 cell extender, so I haven't tried it yet.)

The other one is charging now.

 

[DM51]

Is that 4.02V or 4.20V? If it charged to 4.20 and then dropped back to 4.02, it has lost capacity and should be disposed of.

What about the one that needed the reset? What did that show after a few minutes on the charger?

 

[herbicide]

Just checked it again - 4.02V

Checking other recently-charged cells, they show OK voltages - I've not noticed any problems, anyway...

After ~20mins, the 'dud' showed 0.22V hot off the charger, now 0.09V... 0.06V... T+ 3mins - 0.03V. A dud it is, then.

 

[DM51]

Please bin the dud with alacrity - don't attempt to charge it any more.

Try taking the 4.02V one up to the full charge of 4.20V, then see what it reads about 1 hour after that.

 

[LuxLuthor]

Follow DM-51's advice. For future reference, many of us consider Ultrafire brand similar to cow or dog manure. Trustfire is better, but Pila or AW brands of protected cells are what I use.