Over-discharged NCR18650B - Throw Away???

I pulled the cells out of my Eagtac SX25L3 the other day and they have all virtually drained to nothing. All three of them are reading around 0.17V :(( I don’t know how this has happened because I often go through all my lights and check the cells with my DMM to make sure none of them are getting too low, but this one obviously got past me.

The cells only have 2 cycles on them so they have hardly been used, but should I still just throw them away? They are protected Panasonic NCR18650B cells, so a bit more expensive than your average laptop pull etc!

I understand that often the protection circuits won’t trip when discharging if its such a small current??

Yes, I’m afraid they are past the point where you should not recharge them.


Thanks for confirming what I was thinking. It’s a shame but oh well, these things happen.

Are you sure they’re empty? The protection may have engaged and might need to be reset. Did you try to reset the protection circuit?

Resetting protection circuit

When protection trips, the battery will read 0.00 volts. Since he’s seeing 0.17v that means he’s reading the actual cell voltage.

Sometimes a DMM will give off a small fluctuating reading. Even if there’s nothing there. Nothing to lose by trying to reset it. Before I toss them, I even remove the protection and test them again to make sure.

Hopefully I won’t get flamed for saying this but I would charge them outside and see how it goes. If they don’t get hot or take abnormally long to charge, personally I would continue using them monitoring closely in the future.

I don’t see how two new protected cell could both drain themselves without the protection kicking in. That’s why I’m leery about believing they’re both drained.

Three cells!

I will try resetting them tonight when I get home. Will let you know how I go.

Protection chips apparently don’t trip when under very low current draw. Like you find in some e-switch lights that have high parasitic drain.

*If *you want to go for it, put the charger out side (like in middle of drive way no direct sun) and try charging. I had a Maglite, I built with a faulty driver, kill Two brand new 26650 King Kongs in like 3 days. The were zapped almost like yours. I was able to save them. One at a time on a Xstar charger @ .5 amp charge. Year later cells still going great.
Call me crazy, but try it at your own risk. lol

The only thing that got me, is I understand that parasitic drain usually takes ages to kill a cell.

These batteries have been charged within the last 6 months and there are three of them in the light so I would have thought it would take quite some time to kill them.

Yea, it’s odd. Being a more expensive brand, I’d like to expect Eagtac lights would have low parasitic drain. At least a year to drain full cells. And really I’d want to see 2-3 years.

I had to go see if anyone measured the drain.

fonarevka.ru review (english) 167uA
3400mAh / 0.167 = 848 days, ~28 months

CPF report

3400mAh / 0.640 = 221 days, ~7 months

There we go. It appears that it varies and can be quite high. 7 months is horrid imho.

Can you point out where it says Overdischarge detection will always function regardless of current? Or that it will trigger from cell self-discharge?

I just spent awhile going over it and I am not seeing at all. Just to check that I didn’t miss it, I also used find to search every reference of “overdischarge”, “self-discharge” and even “current”. Nothing.

You can check overdischarge detection at very low currents yourself. Drain a cell to 3v or less (but above the trip point) then attach a resistor selected to drain a few hundred uA. 5KΩ to 30KΩ. You can even do a 1.7v red led + 3-10KΩ resistor so you can see it.

As what some others have sggested, try to jump start the battery in case the protection circuit has tripped.
If the battery is not charging after the jump start or slow charging, carefully remove the protection circuit as the stock batteries may or may not be salvaged.
If the stock battery is also “kaput”, off to the recycle bin it goes.

I had a similar experienced with almost a brand new protected Olight 3400mAh battery (only had 2 charging cycles) and I finally manage to salvage the stock battery.

Well I’m sure glad I asked here!

Did a reset on all of them using a Samsung laptop pull I had and bam, all of them registered at around 2.80v.

I have all three of them on charge in my SkyRC MC3000 at the moment. It must sense that they are low as it is limiting itself to 150mA at the moment even though I set it higher than that.

Thanks for everyone’s input!!

Glad to here it. That was just too weird.

First, I’m happy to see that fact-based troubleshooting has prevailed here. Congratulations on restoring your cells.

Second, as to the excess precision implied (I’m not picking on you Halo, you just expressed the concept the most succinctly), TRY this:

I can generate more DC Volts than that, just by straightening the leads on my trusty (if less than honorable) Fluke 77 IV!

Try it for yourself. Place your DMM in DC Volts mode, Auto Ranging, on the edge of your bench with the leads hanging down. Take the probes w/o touching the metal & simply “flip” them (gently) like reins on a horse-drawn buggy. Or start at the DMM end and pull them together through your fingers to straighten them out. Watch your display.

I get as much as 0.5xx vDC sometimes. Since almost all of you already understand the Physics involved, I won’t insult anyone by explaining the phenomenon of a conductor moving in proximity to another one.

0.00 - 0.17 isn’t significant to me, in a ~4v cell. ‘Margin of error’ and all that rot.

(Full disclosure, I’m prejudiced by having worked on Industrial Automation QA systems where micro-volts at the source determined pass/fail. If you have Nuclear Energy flowing through your mains in the US or Great Britain, You’re Welcome.)

i figured they would be fine.cell rated to 2.5v so not even any loss.now for that defective light….