Dead and resurrected battery

[Stefano]

Sorry for the bad english.


Recently due to a flashlight with a defect (high parasitic discharge) it seems that I have lost two Sanyo NCR18650GA batteries.


The first long time ago I found it empty (the light did not come on) I thought that perhaps the light had remained on or that the battery was defective.
I recharged it and some in time 20 or 30 days this battery it emptied again, in an Xtar VC4 it did not charge, it was seen as: Ni-MH and the charger hand was on 1 V (I don't remember now if the VC4 said 0V or 1V) maybe I tried to recharge it even with a another charger - however this battery has been disposed of.


Later, with an identical battery the same happened, I also tried to measure it with my multimeter (perhaps unreliable) and I saw 1 V.
In VC4 I had the same situation (low voltage, seen as: Ni-Mh, no recharging) I also tried to insert also it in a VP2 but the charger indicator light always remained green without any charge.


I left this battery in the corner for many days waiting to dispose of away.


Today I took it to dispose of it in the appropriate containers but before I inserted it for a moment in the VP2, it immediately went into charge - when the charge started i saw that the voltage was 2.54 V


Charged in VP2 at 0.25 A the voltage in a few moments increased from 2.5 to 2.8 V (too quickly it seems to me ..)
As I write this post the voltage reached 3.35 V (I increased the charge speed to 0.5A)
Inserted for a moment the battery in a flashlight everything seems to work..
This battery may have suffered from too low voltage for an extended period, I don't know if I can trust it.


In the next few days I see if it keeps charging, I still wonder if it can be used safely in powerful lights or if it is better not to consider it a reliable battery anymore.

 

[archimedes]

If I am understanding you correctly, your batteries were Li-Ion and at or around ~ 1V for an extended period of time ? ... not safe

 

[Stefano]

If I am understanding you correctly, your batteries were Li-Ion and at or around ~ 1V for an extended period of time ? ... not safe

Yes, right.
I also know that under 2.5 V the 18650 lithium battery is lost.
I do not explain why the second battery after many days accepts the charge and before not.

 

[Mr. LED]

If I am understanding you correctly, your batteries were Li-Ion and at or around ~ 1V for an extended period of time ? ... not safe

Is it dangerous?

Stefano, Xtar chargers claim they can revive "dead" over discharged batteries. Also maybe the battery after a few days resting, the voltage went back up to a point where it would accept a charge?

 

[archimedes]

The safety issue is not whether or not it holds a charge.

I am not an expert on the chemistry, but my understanding is that (microscopic) sharp metal "spikes" can form, under those conditions, and result in catastrophic internal short-circuit.

Might not happen immediately, and could be triggered by trivial physical stress or jolt (say, a drop, or knock, or bump)

Personally, I would not trust it.

 

[Stefano]

Is it dangerous?

Stefano, Xtar chargers claim they can revive "dead" over discharged batteries. Also maybe the battery after a few days resting, the voltage went back up to a point where it would accept a charge?

I know of this function but both the first and second batteries have been loaded with Xtar VP2/VC4 (perhaps I have also used an MC1S or SC1) with no initial result.
Maybe I should have insisted? I don't remember how much I insisted but I think at least a couple of minutes.

 

[stuart]

Protection circuit?

I'm not an expert on this subject, just adding an experience. About a year or two ago was doing a runtime test on a Malkoff bodyguard with a Keepower 16650. The bodyguard runs on high for about 8 seconds at about 2.1 amps and then steps down. I wanted to see how many 8 second burst one could get out of the battery. The did this over the course of several days. I took a bunch of breaks in order to keep things cool and measure voltage. My last voltage recording was 3.52 Volts. A short time later the battery went completely dead. Voltage measured zero. I panicked and put the battery outside on a concrete patio overnight.

My intention was to safely discard it at some point. Probably stayed outside for about a week. Don't know why, (probably read about it) but decided to charge it and see if the protection had been tripped. Still read 0.00 volts before charging but once I put it in the NItecore D2 charger all was well. I used that battery for another year (never fully trusted it after that) but it worked fine. I assumed that the protection had tripped and that all was well.

Didn't know about the metal "spikes" but that makes sense. I know that car batteries that stay in a discharged state suffer sulfation (basically kind of like rust) and that the metal flakes make contact with each other and short out the cell. If one cell shorts then the lead acid battery is "bad". You can still charge a heavily discharged car battery that has set for a long time, but the more sulfation, the greater the chance of a short and a bad battery. Wouldn't want to take that chance with a lithium.

 

[peter yetman]

Stefano, please just take the battery for recycling.
It is just not worth the risk of it burning you or someone else.
I know it's a challenge to get it going again, but you have raised the chances of having an accident.
Please just get a new one.
P

 

[Mr. LED]

The safety issue is not whether or not it holds a charge.

I am not an expert on the chemistry, but my understanding is that (microscopic) sharp metal "spikes" can form, under those conditions, and result in catastrophic internal short-circuit.

Might not happen immediately, and could be triggered by trivial physical stress or jolt (say, a drop, or knock, or bump)

Personally, I would not trust it.

I didn't know that! Thank you! How low the charge should be so that this could possibly happen? Not to be off topic, but I think it's general safety interest for the group.

 

[WalkIntoTheLight]

Read the specsheet for the battery. Below 2.5v does not necessarily mean the battery is unsafe. For example, the Samsung 30Q specsheet states that under 1.0v the battery is unsafe and should not be recharged. Between 1.0v - 2.5v, charge at 0.1C until above 3.0v, then normal. There's also something about a drain of 10uA below 2.0v.

So, it seems that the cell is fine down to at least 2.0v, and possibly down to 1.0v if you're just dealing with parasitic drain. Below 1.0v, get rid of it.

To be safest, I think 2.0v is the better cut-off point, unless you're sure how it was treated between 1.0v and 2.0v. Different brands may have different cut-offs than the 30Q.

 

[Stefano]

Stefano, please just take the battery for recycling.
It is just not worth the risk of it burning you or someone else.
I know it's a challenge to get it going again, but you have raised the chances of having an accident.
Please just get a new one.
P

Thank you, I have a lot of batteries.
I won't take any risk with this battery.

 

[peter yetman]

Goodoh.
P

 

[archimedes]

I didn't know that! Thank you! How low the charge should be so that this could possibly happen? Not to be off topic, but I think it's general safety interest for the group.

Yes, snd this is not off topic at all here, I would say.

I think that the overall quality of most batteries used by our group is testament to the infrequency of serious problems we see reported on CPF, yet ironically can lead to some complacency about safety issues.

As others have said, the safe voltage range is critically dependent upon the exact chemical makeup and physical structure of the particular cell involved.

Interestingly, the higher the capacity that is stuffed into a fixed size, that tends to increase the risk of potentially dangerous internal shorts (as the onion-like layers separating anode and cathode may be thinner)

Depending on your level of interest in such matters, reading spec sheets may be incredibly boring or quite fascinating

As a general rule, the damage done by undervoltage is time-based, progressive, and irreversible.

For most "normal" lithium ion chemistries, for me personally, I am uncomfortable if the cell has been below 3.0V for any significant duration. Or below 2.0 - 2.5V even briefly.

I tend to be pretty cautious about such things, because why wouldn't one ?

 

[Stefano]

Read the specsheet for the battery

I had to struggle a bit in the end I found this:
The discharge end voltage should be more than 2.5V/cell
(3) Over discharge
Do not discharge the battery less than 2.0V/cell

 

[Mr. LED]

Thanks for all the info guys, I thought I knew enough about batteries but I was wrong. I'll dive in and read a lot more.

 

[peter yetman]

Thanks Stefano, I think we all learnt something from your thread.
P