DM51
Flashaholic
I think this is one of the very few issues where we can say with any certainty that the incan vs. LED argument makes no difference at all!
My Aleph 1 Exploded and cought on fire.
- Thread starter Barefootone
- Start date
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richpalm
Banned
Wow... that hydroflouric acid is some bad s##t!
http://www.emedicine.com/emerg/topic804.htm
Glad you're OK, and definitely keep us posted!
Rich
http://www.emedicine.com/emerg/topic804.htm
Glad you're OK, and definitely keep us posted!
Rich
SilverFox
Flashaholic
Hello Orion,
When cells become unbalanced during discharge, you end up with a strong and a weak cell. At the end of the discharge, the strong cell will try to reverse charge the weak cell. This is when things can get "exciting."
Tom
When cells become unbalanced during discharge, you end up with a strong and a weak cell. At the end of the discharge, the strong cell will try to reverse charge the weak cell. This is when things can get "exciting."
Tom
My hypothesis still is that these events happen near the end of the batteries' lifetime (Question to Barefootone: How old were the batteries? Could they have been near the end of their lifetime?), and that there's a high demand of current from the load during this time.
In the case of Incans, this high current demand stems from the lower resistance of the metal filament when cooling down during dimming.
Now, as I understand this, in both cases when such an event happened with an LED light, it was a REGULATED light. The problem here is that the regulator demands more current towards the end of the battery runtime to keep the power to the LED up.
Still, I think in order for the battery to 'vent with flame' a lot of things must come together. Such as, you need a slightly pre-damaged cell. And a regulator whose cut-off point is too far (all circuitry has some variability -- even if a circuit design is safe and sound, two real circuits based on that design might have slightly different characteristics).
Maybe part of the problem is our preference for flat regulation with LOOONG runtime?
Re: HF. Yes, that's a bad chemical to work with. But there's no need to get paranoid over the HF coming from damaged CR123As. First off, not all CR123A chemistries contain F that can form HF. Second, the amount of HF that can form from a cell that contains F is fairly low.
In the case of Incans, this high current demand stems from the lower resistance of the metal filament when cooling down during dimming.
Now, as I understand this, in both cases when such an event happened with an LED light, it was a REGULATED light. The problem here is that the regulator demands more current towards the end of the battery runtime to keep the power to the LED up.
Still, I think in order for the battery to 'vent with flame' a lot of things must come together. Such as, you need a slightly pre-damaged cell. And a regulator whose cut-off point is too far (all circuitry has some variability -- even if a circuit design is safe and sound, two real circuits based on that design might have slightly different characteristics).
Maybe part of the problem is our preference for flat regulation with LOOONG runtime?
Re: HF. Yes, that's a bad chemical to work with. But there's no need to get paranoid over the HF coming from damaged CR123As. First off, not all CR123A chemistries contain F that can form HF. Second, the amount of HF that can form from a cell that contains F is fairly low.
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I wonder if matching new cells by no load voltage would eliminate this risk, and if so, how close they have to match?
Khaytsus
Enlightened
I didn't mean to imply that he'd done anything wrong.. But one way or the other, it appears the cells were mismatched or just plain faulty.
Has this happened on any 1x123 cells that anyone knows of?
fieldops
Flashlight Enthusiast
Yeah, looks like an equal opportunity exploder, I'm afraid. Not good.
luigi
Enlightened
Yes, it happened with a Fenix P1D
https://www.candlepowerforums.com/threads/169038&highlight=exploding
Luigi
half-watt
Flashlight Enthusiast
I've read this claim here on these Forums before. I'd like to know how that works. Obviously, i must be missing something that's very clear to y'all.
Here's my mental problem. If we had two cells in parallel, i could buy into that explanation. However, we have two cells in series. How does the strong cell try to charge the weaker cell? Normally, charging occurs in the reverse direction of discharge. If we want to speak of it as electrons flowing, then we force electrons into the positive terminal of the battery which is inserted in the battery charger - a crude, but perhaps accurate enough description for our purposes.
How does this happen with two cells in series? I just don't see how we reverse current flow. *IF* current flow were reversed, then wouldn't a device with polarity requirements (like a semiconductor) be reversed biased and either not work, or "blow"? So, even if this could occur, our LED light with associated electronics would no longer be working and producing light.
now, if you're going to tell me that the weaker cell undergoes pole reversal (pos. becomes neg. and neg. becomes pos. - this can actually occur during long term storage under self-discharge conditions, but the voltage falls THROUGH and PAST OVDC potential state and then reverses), then that cell must have passed through a 0VDC potential state just before undergoing pole reversal. are y'all saying that this occurs in such a short time frame? i would think that if this occurred then some devices would stop functioning due to the fact that a single cell produces insufficient voltage to power the device.
i'm not so sure that this "reverse charge" is taking place. i just don't see a complete current path for such to occur. why wouldn't the stronger cell be reverse charing itself (not that this would occur)? it still has poles, does it not?
so, what precisely is happening to the poles areas in the stronger cell? i could buy into electron migration of some type in the chemical paste of the battery in the weaker cell caused by the difference in potential between the two cells, but not charging. i just can't envision how that would occur based upon the inviolate basic physical and electrical principles involved. what am i forgetting or missing? would someone please tell me? i'm very confused at this point on something that seems real clear to y'all.
does anyone see my intellectual dilemma on this issue? or, is my Post unclear?
would appreciate any education y'all can give me. many thanks.
now, i think i'll go and THINK! THINK! THINK! on this matter even though my brain already hurts.
many thanks to those who will try to help me,
half-watt (or is that "half-wit"!!!)
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Check Newbie's thread on this topic. I think it's essential reading for anyone using CR123 based lights:
https://www.candlepowerforums.com/threads/124776
Hans
BB
Flashlight Enthusiast
Several issues, some battery chemistries are pretty save to take down to ZERO volts (NiCads IIRC). Other chemistries are dangerous to take down below a certain minimum voltage, they will become "unstable" (Lithium Ion rechargeables--have individual cell protection built-in). Others, have varying issues too (high current, internal shorts, plating of pure lithium metal out of the matrix in certain conditions, etc.)...
In general, primary type CR123A Lithium cells are assumed to be pretty safe to zero volts (may be some other chemistry, manufacturing, etc. issues--ignoring for now).
So, if you have one battery--discharging to zero volts should be OK (other than leaving a discharged battery in a light can increase chances of leaking).
Place two CR123's in series on a filament Halogen bulb, if one battery is new, and one battery is used, you will quickly see the filament yellow as the used battery voltage fails--giving visual clues that the battery pack is going bad/discharged.
If the light was left one, eventually the voltage of the used cell drops to zero, and the good cell will start to "reverse charge" or cause pole reversal and charging on the used battery. Most batteries will be destroyed by this action--and some will become dangerous as the chemistries start to do things they were never intended to do.
With regulated LED lights, and multi cell lights, the chances that any one cell in the pack can get reversed biased (weak cell compared to other cells in packed--unbalanced pack design, etc.) increase as it can be very difficult to know when a cell in a pack is getting reversed.
For example, a 12 volt NiCad pack uses 10 cells. The difference in output voltage of a pack near discharge vs a pack with 9 good cells and 1 bad cell is very difficult to determine without metering every cell (like protection required for a Lithium Ion pack).
Anyway, read the NewBie thread--lots of examples and how-to's to make failures.
-Bill
half-watt
Flashlight Enthusiast
search OP Post for all references to "charg" and read context in which the search term was located.
did not answer the question of how a weaker cell could be charged by a stronger cell when both cells are in series. did i miss it?
i don't dispute whatsoever that there is a problem. i'm only questioning the commonly heard explanation of how this occurs, viz. a stronger cell charging a weaker cell in series.
excellent Thread by the way, many thanks for the hyperlink to it.
half-watt
Flashlight Enthusiast
BB, many thanks for the swift and comprehensive reply. I mentioned "Pole Reversal" in my Post to which you're replying as the only possible way i could see two cells in series performing a charging action. Many thanks for the confirmation that this is the reason for the "exploding" batteries.
So, like i also mentioned in that Post, a LED light with electronics should no longer be working when this condition occurs, and as you stated an incandescent light should only have its filament glowing.
Good clues that there is a problem a brewin'.
it didn't sound though from some of the Posts in various Threads that i read, that the light was no longer functioning just before the explosion. i, perhaps erroneously, got the picture of a perfectly good working light and then seconds later, or a very short time later after being switched off or placed down, or the user noticing that the flashlight was getting a mite hot, and then BLAMO or KABOOM. So, how was the light functioning so well, on only one cell? This confuses me. Any thoughts?
David_Campen
Enlightened
No, the LED could still work. The still good batteries would bias the LED in the proper direction and current would (could) still be flowing through the LED. If no curent was flowing through the LED there would be no current to reverse charge the bad cell.
Gazoo
Enlightened
Maybe the regulation circuitry in the flashlight is so good one wouldn't notice if it was only running on one battery, which would be around 3 volts? But this has me concerned too. I have a laser on the way that takes 2 CR123A primaries, and it has regulated circuitry. I think I will measure the voltage of each battery every couple of days or so just to play it as safe as I can. I have a 12 pack of Panasonic batteries I am going to use.
half-watt
Flashlight Enthusiast
only partially agree here. your point about the LED must be on for the pole reversed weaker cell to be charged is certainly correct - no doubt about that.
however, in some designs (without boost converter) 3V is insufficient to forward bias the LED, and this doesn't even consider any voltage drops across the weak cell or anywhere else in the electronics. how many 2xCR123A designs have a boost converter?
BB
Flashlight Enthusiast
Read through the NewBie thread... With two cell lights/simulations, he took one partial discharged cell and one full cell (primaries in this case), and ran them under load until "something" happened...
What was interesting, in at least one of the cases, it was the 100% new cell that vented--not the partially used cell...
Why--possibly the partial cell got hot, headed the "new" cell, and when the cell(s) failed internally, only the "new cell" had enough energy to overheat and vent. So, in this case, it would be assumed that it was not the polarity reversal of the "used cell" that "failed"--but it may have contributed to the venting of the other cell because of overheating.
In any case, the failure modes and mechanisms are numerous and varied. Some are probably happening in flashlights that have not been used for a while, others in flashlights the are even perfectly functioning until they got hot, made noise, "went dark" a few moment before, etc...
There appears to be no one failure mode--But the majority failures in primary lithium cells appear to be broken into to classes of causes--1) Heat--whether because of high current, "weak" cell in string, environmental; and 2) mechanical damage--dented cells from over-tightening, dropping, etc.--once "damaged" the massive amount of current available inside the battery causes internal shorts and I^2*R heating and/or chemical heating.
I have not read the whole thread yet--but most of the failures seem to involve two or more cells in series. Yet, there was, apparently, at least one failure noted (Air Canada incident?) with a single cell light that may have been dropped on the floor of the aircraft by a passenger.
In the end, these batteries have very reactive components and are able to release large amounts of energy in a short amount of time... Perhaps Lithium flashlights need a frangable spot or other venting system to help reduce propelling parts of the lights ("explosions") when failures occur.
Problem is that this will add costs, size, difficulty to change cells, and could reduce water resistance and such...
Problem is real, appears to be rare (unless abused on purpose), and is the cure worst than the problem.
In the end, the current rules that keep the size of the batteries small for use on airplanes and excluding from nuclear power plants may be enough.
In the case where a small "venting with flame and flying debris" incident is not acceptable, either the light(s) need to be redesigned or accept using alternative energy sources (alkaline or other chemistries/constructions).
The neat thing is with the high efficiency LEDs, these alternative sources of power can give just about equal performance with far less risk of "dangerous" failures.
-Bill
What was interesting, in at least one of the cases, it was the 100% new cell that vented--not the partially used cell...
Why--possibly the partial cell got hot, headed the "new" cell, and when the cell(s) failed internally, only the "new cell" had enough energy to overheat and vent. So, in this case, it would be assumed that it was not the polarity reversal of the "used cell" that "failed"--but it may have contributed to the venting of the other cell because of overheating.
In any case, the failure modes and mechanisms are numerous and varied. Some are probably happening in flashlights that have not been used for a while, others in flashlights the are even perfectly functioning until they got hot, made noise, "went dark" a few moment before, etc...
There appears to be no one failure mode--But the majority failures in primary lithium cells appear to be broken into to classes of causes--1) Heat--whether because of high current, "weak" cell in string, environmental; and 2) mechanical damage--dented cells from over-tightening, dropping, etc.--once "damaged" the massive amount of current available inside the battery causes internal shorts and I^2*R heating and/or chemical heating.
I have not read the whole thread yet--but most of the failures seem to involve two or more cells in series. Yet, there was, apparently, at least one failure noted (Air Canada incident?) with a single cell light that may have been dropped on the floor of the aircraft by a passenger.
In the end, these batteries have very reactive components and are able to release large amounts of energy in a short amount of time... Perhaps Lithium flashlights need a frangable spot or other venting system to help reduce propelling parts of the lights ("explosions") when failures occur.
Problem is that this will add costs, size, difficulty to change cells, and could reduce water resistance and such...
Problem is real, appears to be rare (unless abused on purpose), and is the cure worst than the problem.
In the end, the current rules that keep the size of the batteries small for use on airplanes and excluding from nuclear power plants may be enough.
In the case where a small "venting with flame and flying debris" incident is not acceptable, either the light(s) need to be redesigned or accept using alternative energy sources (alkaline or other chemistries/constructions).
The neat thing is with the high efficiency LEDs, these alternative sources of power can give just about equal performance with far less risk of "dangerous" failures.
-Bill
BB
Flashlight Enthusiast
Also, some batteries get quite warm when near discharged and operating under load (still able to supply sufficient current to operate the device)... Alkaline batteries do this for me (don't know about Lithium primaries).
-Bill
-Bill
half-watt
Flashlight Enthusiast
noticed that before when i read the OP's Post in that Thread. agree that there must be multiple reasons for these problems and not just one failure mode. this is part of the problem i've had accepting the simplified panacea explanation that is often offered of stronger cell charging the weaker cell. the owner/user description of the problem often speaks of a perfectly functioning light with no problems other than it gets very hot but is still functioning normally. in my experience, this isn't what happens when pole reversal occurs. this indicated to me that another failure mode of the cell(s) was occurring.
that charging occurs IF pole reversal has taken place i have no problem with, as i stated, i know this occurs. however, a device still functioning normally when this occurs (i've had a number of NiCd and NiMh cells undergo pole reversal and seen the effects in both lights and cordless power tools - have NEVER seen a device continue to function normally when this happens - the dead cell just isn't pulling its weight for the device to continue functioning NORMALLY - whether cordless drill or worklight. could it continue to work perfectly in some designs? i'd say 'yes' in the right design (like maybe one with a boost converter which allows lower voltages, like from a single cell, to still power the device properly?). i'd GUESS that there are not too many multi-cell powered designs (those using 2 or 3 123A cells - not AA cells - these would still need some boost for 2xAA to fwd bias an LED) that employ a combination buck-boost converter. certainly there are some. wonder if they were present in the lights with exploding cells?
other failure modes (a short for instance) certainly could have the device functioning normally is my guess - for a short time at least, until KABOOM.
anyways, BB, you've help clarify a lot of things for me. thank you. at least i know now that CPF doesn't think every failure is a result of the stronger cell charging the weaker cell.
Illum
Flashaholic
I ZTS my cells after every lengthy discharge if I can...and whether its the surefire G2 or the inova XO3 I have found cases were surefire cells that were 100% at start ended up with something like 80/20 or even a 80/zip
every pair that are unbalanced are discharged in single cell dorcys and so far other than the P1D accident theres have been no reports of single cell lights venting
in my experience so far the only double celled light I have that gives me consistent readings from both cells from start to finish is the surefire A2
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