Did my 18650 vent?

[snowlover91]

I have a Trustfire 18650 protected battery that I was using in my Ultrafire C2 MC-E light. I unscrewed the head and soldered a spring so I could also use unprotected trustfire batteries in my light. Well I put a protected 18650 in there, and tried to measure the amps with my voltmeter. All of a sudden, the display read like 12 amps of electricity, and smoke started coming out of the battery tube very fast! I quickly stopped what I was doing. Now my question is, did the 18650 vent? I don't see really any residue, but it shows the voltage at 0 on my meter now. I took an unprotected 18650 in my C2 after this and it worked fine. Also, why would the spring make what I described happen? I had everything on my meter set up right to measure the amp pull, and I hooked the Leads up correctly also. The light still works so fortunately I didn't fry the MC-E led.

 

[JohnMuchow]

Smoke + Zero Volts = Fried Battery
Yup, it most definitely vented. Any smoke is a very, very bad thing.

Not sure why it happened but that battery is gone.

John

 

[mdocod]

your spring mod probably has an intermittent short.... Your trustfire's protection circuit probably wasn't very trustworthy...

We don't get very many reports of venting li-ion cells around here, as they tend to be very safe, but ~9/10 reported incidents are user error, and the other ~1/10 tends to be cheap cells. In your case, I believe there may have been some user error (somehow you shorted the cell with your modification IMO) but there was also some cheap-cell component to this failure as well, as a well made cell will not vent from being shorted by accident for a little while, even an unprotected cell made properly would survive some abuse before going evil-vent-time.

 

[snowlover91]

your spring mod probably has an intermittent short.... Your trustfire's protection circuit probably wasn't very trustworthy...

We don't get very many reports of venting li-ion cells around here, as they tend to be very safe, but ~9/10 reported incidents are user error, and the other ~1/10 tends to be cheap cells. In your case, I believe there may have been some user error (somehow you shorted the cell with your modification IMO) but there was also some cheap-cell component to this failure as well, as a well made cell will not vent from being shorted by accident for a little while, even an unprotected cell made properly would survive some abuse before going evil-vent-time.

So what do you guys think about using the spring with an unprotected 18650? All it is is a spring that is on the contact plate of the LED, just like in some of my other lights, I don't know how this would be shorting the battery though? Does an unprotected 18650 have these same safety features? Should I not use the spring then? Maybe somehow the spring and the protected battery along with me measuring the amp draw caused it to happen, because the light is working fine with unprotected 18650 batteries?

 

[mdocod]

what i mean is, in the way that you attached the spring may have somehow caused a short somewhere.. I'm not sure what the situation looks like... but imagine... what if the spring bend over or smashed out in such a way that it made contact with the body... there's lots of possibilities but you'd have to inspect the situation to make sure...

When I say that an "unprotected" battery shouldn't vent under these circumstances, I am not implying that there are any safety features in place like a PCB to prevent it, I mean that a well made unprotected cell, would be built well enough that shorting it out for a few seconds would NOT cause it to vent. Yes it would still short out and deliver a lot of current into a dead short, but it should be able to handle that a few times.. I'd almost bet money that I could take a decent quality li-ion cell, and discharge it into a dead short at least a few times before it exploded. I still suggest the use of only protected cells, as protection circuits will help extend the life of a LiCo cell when used in applications where they may be inadvertently over-discharged/charged or shorted, which are all possibilities when dealing with loose cells. Even "experts" have made mistakes.... Yes I have fallen asleep with cells on my WF-139 (old style) a few times, and woke up to cells at 4.30V and climbing... not good....

I'm trying to think of any other reasons for the short...

Like maybe your protected cell had a tear in the shrink-wrap somewhere?

It's always a good idea to try to figure out what caused a problem like this, so that we can know what *not* to do again

Eric

 

[snowlover91]

Nope, no tears in the wrapper. It is possible that since the spring was loose when I initially tried it, that somehow it made contact with the body and created a short, but it didn't do this with the unprotected cell? Weird isn't it? I am just glad my 18650 didn't explode, that could have been ugly!

 

[mdocod]

maybe the PCB shorted and it was a coincidence... maybe the smoke was the PCB frying and not the cell at all....

 

[LukeA]

Measuring amps is what caused this. Measuring amps creates a dead short between the probes. It's not a problem with the mod.

You are very lucky the cell didn't explode. You can probably thank the protection circuit for that. If you have to ask questions about what you're trying to do, you shouldn't do it, especially with unprotected cells. You can seriously hurt yourself.

Also, why are you attempting to attach anything to the 18650 itself? Nothing requires that. You can attach the spring to the driver board without danger to yourself.

 

[snowlover91]

Measuring amps is what caused this. Measuring amps creates a dead short between the probes. It's not a problem with the mod.

You are very lucky the cell didn't explode. You can probably thank the protection circuit for that. If you have to ask questions about what you're trying to do, you shouldn't do it, especially with unprotected cells. You can seriously hurt yourself.

Also, why are you attempting to attach anything to the 18650 itself? Nothing requires that. You can attach the spring to the driver board without danger to yourself.

I did it right, I watched videos and did it the correct way. I put the black lead on the - end, and the red lead on the thread contacts, isn't that the correct way to do it?

I didn't attach the spring to the 18650, I was attaching it to the circuit driver board. I am glad it didn't explode.

 

[mdocod]

Measuring amps is what caused this. Measuring amps creates a dead short between the probes. It's not a problem with the mod.

You are very lucky the cell didn't explode. You can probably thank the protection circuit for that. If you have to ask questions about what you're trying to do, you shouldn't do it, especially with unprotected cells. You can seriously hurt yourself.

Also, why are you attempting to attach anything to the 18650 itself? Nothing requires that. You can attach the spring to the driver board without danger to yourself.

I think you misunderstood his entire post.... He didn't attach anything to the cell and didn't short out the cell with the DMM leads. (well, technically he did, but his method of measuring current across where the tail-cap would have been was correct, there had to have been a short somewhere else to cause this connection to become the dead short, rather than the normal circuit closing function that the switch would have ordinarily done).

 

[MorePower]

Measuring amps is what caused this. Measuring amps creates a dead short between the probes. It's not a problem with the mod.

Clearly, the OP was measuring amps drawn by the LED, not through a dead short of the battery.

You are very lucky the cell didn't explode. You can probably thank the protection circuit for that. If you have to ask questions about what you're trying to do, you shouldn't do it, especially with unprotected cells. You can seriously hurt yourself.

No need to get all holier than thou; the OP did nothing wrong in trying to measure current draw in that manner. It was the correct way to do so.

Also, why are you attempting to attach anything to the 18650 itself? Nothing requires that. You can attach the spring to the driver board without danger to yourself.

Again, it's pretty clear from the first post that the OP attached the spring to the head of the light, not to the 18650.

 

[Illum]

what i mean is, in the way that you attached the spring may have somehow caused a short somewhere.. I'm not sure what the situation looks like... but imagine... what if the spring bend over or smashed out in such a way that it made contact with the body... there's lots of possibilities but you'd have to inspect the situation to make sure...

solder will flow into any metal part you heat up along with the spring. it may also be likely that during your little experiment you've reflowed the existing solder somewhere on the light...and that caused the short
or..
the spring closed a gap that leads to the short, but still a gap remained...it just so happened for that particular battery lowered into it in that position caused the`short on contact, which may explain why the other battery you tried does not have the same effect

 

[snowlover91]

solder will flow into any metal part you heat up along with the spring. it may also be likely that during your little experiment you've reflowed the existing solder somewhere on the light...and that caused the short
or..
the spring closed a gap that leads to the short, but still a gap remained...it just so happened for that particular battery lowered into it in that position caused the`short on contact, which may explain why the other battery you tried does not have the same effect

The 2nd reason sounds more likely. I was careful to make sure no solder went anywhere else, so I think it had something to do with the spring. Could it be the spring touched the wall (case) of the light while also touching the circuit board, causing the short?

 

[mdocod]

Could it be the spring touched the wall (case) of the light while also touching the circuit board, causing the short?

That was what I was talking about before, if the cell were able to squish the spring over in such a way that it made contact with the body, then you would have a dead short as soon as you tried to measure current... If the inside of the body is bare aluminum then this is very likely...

 

[Fallingwater]

My two cents: the smoke most likely came either from the protection PCB burning out or from dirt on the shorting spring.
It's easy to test the PCB; put the cell in a charger for a few seconds, pull it out, measure voltage. If it reads normal LiIon voltage, the PCB is fine. Otherwise it probably won't even charge; in this case you can cut away the plastic casing and bodily rip out the protection circuit from the cell, and you'll most likely have a working unprotected 18650.

If the PCB is fine, then the smoke probably came from the spring. 12 amps flowing through a thin bit of metal causes a hell of a lot of heat, and whatever dirt and grease might have been on the spring evaporated and filled your light with smoke.

Then again, when a spring overheats it's usually visible to the naked eye, as the metal changes colour and the spring is much less, er, springy than before.

You are very lucky the cell didn't explode.

Not really. Metal-cased LiIon cells that aren't meant for very high discharge rates are pretty safe. Even if you short an unprotected one they have protection inside that will permanently disable them if dangerous conditions are reached. Well, 18650s have, anyway.

 

[snowlover91]

That was what I was talking about before, if the cell were able to squish the spring over in such a way that it made contact with the body, then you would have a dead short as soon as you tried to measure current... If the inside of the body is bare aluminum then this is very likely...

My two cents: the smoke most likely came either from the protection PCB burning out or from dirt on the shorting spring.
It's easy to test the PCB; put the cell in a charger for a few seconds, pull it out, measure voltage. If it reads normal LiIon voltage, the PCB is fine. Otherwise it probably won't even charge; in this case you can cut away the plastic casing and bodily rip out the protection circuit from the cell, and you'll most likely have a working unprotected 18650.

If the PCB is fine, then the smoke probably came from the spring. 12 amps flowing through a thin bit of metal causes a hell of a lot of heat, and whatever dirt and grease might have been on the spring evaporated and filled your light with smoke.

Then again, when a spring overheats it's usually visible to the naked eye, as the metal changes colour and the spring is much less, er, springy than before.

Not really. Metal-cased LiIon cells that aren't meant for very high discharge rates are pretty safe. Even if you short an unprotected one they have protection inside that will permanently disable them if dangerous conditions are reached. Well, 18650s have, anyway.

mdocod, I think what you mentioned is very possible. The inside is bare aluminum, and it is possible that the spring squished out enough to contact and aluminum and caused the short you mentioned.

Fallingwater, I stuck it in the charger for 1 minute, and measured voltage. 0.00 was the reading, then tried a rcr123 an measured 4.09, so the battery is definately dead. I think I will just dispose of this battery, I don't know really where the smoke came from and want to be on the safe side of things. Thanks for the help everyone, now I have an excuse to order some AW 18650 cells.

 

[mdocod]

Not really. Metal-cased LiIon cells that aren't meant for very high discharge rates are pretty safe. Even if you short an unprotected one they have protection inside that will permanently disable them if dangerous conditions are reached. Well, 18650s have, anyway.

PTC devices are not found in all 18650s from what I have heard, but more importantly, most cheaper PTC devices are not capable of stopping a thermal runaway situation once it has started anyways.

 

[Fallingwater]

Fallingwater, I stuck it in the charger for 1 minute, and measured voltage. 0.00 was the reading, then tried a rcr123 an measured 4.09, so the battery is definately dead. I think I will just dispose of this battery, I don't know really where the smoke came from and want to be on the safe side of things.

At least measure the voltage behind the protection. You don't even need to peel off all the plastic, just cut enough to access a bit of metal on the side of the battery and put the negative probe of the meter there.
If it says 0V even in that case then yeah, trash it, otherwise it's definitely just the protection circuits that burned up.

PTC devices are not found in all 18650s from what I have heard, but more importantly, most cheaper PTC devices are not capable of stopping a thermal runaway situation once it has started anyways.

Hmm. This would require testing. We need volunteers with insurance

 

[Oznog]

There is no way a cell failure can cause 12 amps of current to flow into a functioning circuit. An internally shorted cell may draw tens of amps flowing inside the cell but not out through the terminals where an ammeter could measure it.

Therefore, it looks like he created a short for sure, either with the meter itself going from + to - without being in series with the load or maybe something else hooked up funny shorted the battery.

But you DID make a short for sure. The battery could not have caused high current on its own.