Are lithiums safe as long as they are not in series?

[Poppy]

I think the title pretty much says it all.
"Are lithiums safe as long as they are not in series?"

I've read many, but not all of the threads in this section, and it seems to me that the problems with lithiums and fires, occurred for the most part, years ago, and more often than not when two batteries were put in series.

Further the problems with batteries in series occurred when the batteries were of different capacities, and or charged to different levels.

Some threads or at least individual posts suggest that with the advent of protected cells, there isn't much of an issue anymore.

Its my understanding that one still needs to be aware, when charging an over-discharged battery that there may be a fire, but that should be a concern only after it has been depleted to the point that the over-discharge protection circuit has tripped.

I only have one light that I use CR123s in series, (it won't fit an 18650) and won't buy another due to the fire concern. Am I correct about about being concerned?

 

[archimedes]

I think it would be fair to say that single-cells are generally safer than batteries in series.

Even single cell batteries have certain safety risks, however, protected or not. Any battery may short-circuit, for example, releasing a lot of energy (particularly for lithium-based chemistries). Batteries in a handheld device (such as a flashlight) are at risk of being physically damaged, when dropped.

Some risks may be unique to the specific battery chemistry, while others may be more general.

 

[SilverFox]

Hello Poppy,

The main concern during use comes when you have 2 or more cells in series and they are not all at the same charge state. This applies to both primary and secondary cells. A weak cell can suffer from reversed polarity in this situation and that may cause rapid venting sometimes accompanied with flame.

A secondary battery made up of several cells in series can also have problems when charging if no attention is paid to balancing the cells during the charge. In this case it is possible to overcharge the other cells in the battery pack. Another issue can manifest itself when charging a cell that has been over discharged.

A secondary cell that has a protection circuit should eliminate the over discharge concern. If you rely on the protection circuit to tell you when the cell is empty you will most likely not enjoy full cycle life from the cell but the protection circuit should keep you from experiencing problems during recharging.

It comes down to factoring the risks and rewards.

Tom

 

[lightcycle1]

I had my first run in with a single cell setup today.

and this was with a high quality protected cell.

granted, the small accident I had was my fault.

The flashlight crushed the protection circuit on the cell and it shorted. It was an eye opener. Burned my finger but could have been worse.

http://www.cpfmarketplace.com/mp/showthread.php?p=4766447

Sent from my SCH-S720C using Tapatalk 2

 

[archimedes]

....A secondary cell that has a protection circuit should eliminate the over discharge concern. If you rely on the protection circuit to tell you when the cell is empty you will most likely not enjoy full cycle life from the cell but the protection circuit should keep you from experiencing problems during recharging....

Although perhaps not relevant for all torches (depending on the specifics of the driver), my understanding is that a very low current draw may still cause over-discharge, even in protected cells .... I have had difficulty finding a reference source for how small this must be to "escape" the typical protection circuit - how low do you think this might be ?

 

[SilverFox]

Hello Archimedes,

I don't know what current is able to bypass the protection circuit. I remember it being discussed before but can't seem to find the discussion.

In addition for those lights that are less frequently used you need to remember that the protection circuit also draws a small amount. However I believe it would take several years to completely drain the cell just from the protection circuit.

Tom

 

[archimedes]

Thanks, I'll keep looking .... I always enjoy your informative posts, by the way - :thumbsup:

 

[Poppy]

SilverFox, and Archimedes,
Thank you both, for responding to my questions. I appreciate your knowledge and willingness to share.

lightcycle1,
Thanks for sharing an issue I was not aware of. I'll be sure to check my battery/s (for compression damage) the next time I drop any one of my lights. Hehehe... and I DO drop them.

 

[lightcycle1]

actualy it seems as if it were a squeeze damage from the cell possibly being too long for the light. I used an ET3100 18650. I just bought the modded light a few days ago. Seller stated he only used AW 2900's in the light which according to him are shorter. I havnt researched this yet but for the time being the light will be shelved. I dont trust it and I dont need a light smoking brand new 15-20$ cells either. I was a little upset as that ET3100 was essentially brand new with only a few charge cycles on it.

As far as the hot-vent incident, the protection circuit did its job and the cell was stable, smoked, but stable until I tried to get cute with it and remove the protection circuit chips thinking I could use the cell as a flat-top unprotected one. It didnt like that one bit and it spit hot gas on my finger, and lt was HOT. As in super-heated and it happend in a split second. I was more scared of the fumes. Thankfully the gas was minimal and I didnt get a bad noseful of it bit the little bit that did escape was very acrid and chemical smelling.

Moral of the story: Don't screw with a cell gone bad.
My first instinct was to dispose of it immediatly.
Should have done that but my curiosity got the better of me.

Stupid. Never again. Live and learn I guess.

Sent from my SCH-S720C using Tapatalk 2

 

[lightcycle1]

FWIW.
Appears that cell length is not the issue.

Sent from my SCH-S720C using Tapatalk 2

 

[Poppy]

lightcycle1,
Thanks for posting.
I read the link that you provided above, and since *I* rarely follow links within threads, I'd like to add a synopsis of that thread here for others who may read this thread in the future.
In brief, the host light was modified with a shortened body. So short that the tail cap could not be screwed on all the way. IF it WAS screwed on all the way, it would have crushed ANY 18650 battery's protection unit and destroyed the battery. The AW 2900 is actually a little longer than the ET 3100.
The modified host destroyed the battery, and poking at the battery with a knife caused it to short, overheat and vent.

LOL... maybe I should change the title to "Are lithiums safe as long as they are not in series, or crushed in a shortened body, or poked at with a knife?"
Thanks for fessing up.

 

[darkangel55555]

...or shorted out, or heated up (like in a car parked in the sun)...

Also, the way you've phrased the question leaves the opening to interpret it as "...not in series, but instead alone or in parallel?", which is of course not the case. Cells in parallel can reverse charge each other even more easily, though they should not completely invert polarity (unless someone put one cell in a carrier backwards, in which case you've got more to worry about).

 

[Poppy]

...or shorted out, or heated up (like in a car parked in the sun)...

Also, the way you've phrased the question leaves the opening to interpret it as "...not in series, but instead alone or in parallel?", which is of course not the case. Cells in parallel can reverse charge each other even more easily, though they should not completely invert polarity (unless someone put one cell in a carrier backwards, in which case you've got more to worry about).

Well, yes, my understanding is that for the most part lithiums are safe when used singly or in parallel. You state that is NOT the case. Please enlighten me.

I'm thinking that putting them in parallel will be relatively safe, in that the flashlight's protection should kick in when the batteries' voltage drops low enough, and when in parallel, the batteries should have the same voltage, because as you stated they would back feed each other.

 

[Poppy]

...or shorted out, or heated up (like in a car parked in the sun)...

Also, the way you've phrased the question leaves the opening to interpret it as "...not in series, but instead alone or in parallel?", which is of course not the case. Cells in parallel can reverse charge each other even more easily, though they should not completely invert polarity (unless someone put one cell in a carrier backwards, in which case you've got more to worry about).

According to Battery University... Li cells are stable, depending upon their chemistry between 302F and 450F, yet according to another study the inside of a car in various outside temps in the sun can get up to 160F.
If I am interpreting that data properly, there is no specific danger to leaving a Li battery in a car. (maybe not on the dash)
Also according the Battery University, the protection circuit has a thermal cut off, at 194F.

[FONT=Arial, Helvetica, sans-serif]Let me assure the reader that lithium-ion batteries are safe and heat related failures are rare. The battery manufacturers achieve this high reliability by adding three layers of protection. They are: [1] limiting the amount of active material to achieve a workable equilibrium of energy density and safety; [2] inclusion of various safety mechanisms within the cell; and [3] the addition of an electronic protection circuit in the battery pack.
[/FONT]

[FONT=Arial, Helvetica, sans-serif]Lithium-ion cells with cobalt cathodes (same as the recalled laptop batteries) should never rise above 130°C (265°F). At 150°C (302°F) the cell becomes thermally unstable, a condition that can lead to a thermal runaway in which flaming gases are vented.

During a thermal runaway, the high heat of the failing cell can propagate to the next cell, causing it to become thermally unstable as well. In some cases, a chain reaction occurs in which each cell disintegrates at its own timetable. A pack can get destroyed within a few short seconds or linger on for several hours as each cell is consumed one-by-one. To increase safety, packs are fitted with dividers to protect the failing cell from spreading to neighboring cells.
[/FONT] [h=2]Safety level of lithium-ion systems[/h] [FONT=Arial, Helvetica, sans-serif]There are two basic types of lithium-ion chemistries: cobalt and manganese (spinel). To achieve maximum runtime, cell phones, digital cameras and laptops use cobalt-based lithium-ion. Manganese is the newer of the two chemistries and offers superior thermal stability. It can sustain temperatures of up to 250°C (482°F) before becoming unstable. In addition, manganese has a very low internal resistance and can deliver high current on demand. Increasingly, these batteries are used for power tools and medical devices. Hybrid and electric vehicles will be next.[/FONT]

 

[darkangel55555]

Well, yes, my understanding is that for the most part lithiums are safe when used singly or in parallel. You state that is NOT the case. Please enlighten me.

I'm thinking that putting them in parallel will be relatively safe, in that the flashlight's protection should kick in when the batteries' voltage drops low enough, and when in parallel, the batteries should have the same voltage, because as you stated they would back feed each other.

They are mostly safe when used in series. In parallel, the carrier can let them short until they are balanced - if this is sufficient to elevate the temperature beyond the envelope's failure, you will have a bad time.

Direct sunlight (and poorly designed/manufactured cells) can cause a failure where the ambient temperature is below 130F. I would personally worry more about cells where the envelope is thinner than spec, or the cap is improperly crimped to the casing. Basically, buy quality. That doesn't mean buy American, but American cells are of high quality, as are Japanese cells. The majority of the cells coming out of PRC I would be cautious (read:extremely cautious) about. I'm too pretty to die.

 

[moldyoldy]

I think the title pretty much says it all.
"Are lithiums safe as long as they are not in series?"
<snip>

no.

I gave a Fenix P1 (1x CR123 cell) and some lower-cost primary CR123 cells to a friend. He had the light turned on in his basement when suddenly the cell blew out the front lens with lots of noxious fumes, but relatively little fire. I sent the remains to Silverfox who investigated the resulting mess. Initially I was incorrect about which cell it was. It was indeed a single primary Lithium CR123 cell that rapidly disassembled itself.

The point is that even single Lithium cells can be dangerous. The brand was low-cost, but still well known. Since then I purchase only higher-quality CR123 cells for any of my acquaintances who still use the CR123-based lights that I gave them. I am attempting to move them all over to AA/Eneloop or 18650 protected cells - and thereby losing the considerable investment in the CR123-based lights. Even one failure is too many, especially for non-flashaholics!

 

[LEDninja]

Single rechargeable lithium ions can explode if
The charger charges them above 4.2V;
The charge or drain rates are above spec.;
The voltage drops below 2.7V.

I do not use my 18650 often and have thrown out many that have self discharged themselves to zero.

 

[BillSWPA]

no.

I gave a Fenix P1 (1x CR123 cell) and some lower-cost primary CR123 cells to a friend. He had the light turned on in his basement when suddenly the cell blew out the front lens with lots of noxious fumes, but relatively little fire. I sent the remains to Silverfox who investigated the resulting mess. Initially I was incorrect about which cell it was. It was indeed a single primary Lithium CR123 cell that rapidly disassembled itself.

The point is that even single Lithium cells can be dangerous. The brand was low-cost, but still well known. Since then I purchase only higher-quality CR123 cells for any of my acquaintances who still use the CR123-based lights that I gave them. I am attempting to move them all over to AA/Eneloop or 18650 protected cells - and thereby losing the considerable investment in the CR123-based lights. Even one failure is too many, especially for non-flashaholics!

Do you remember the specific brand of CR123 primary that caused the problem?

I have only used Duracell, Energizer, and Surefire CR123, and 100% of my current inventory is Surefire. However, lately I have been getting into single-cell CR2 lights, and, upon reading many positive comments about a particular brand of first-tier Chinese made cell, bought a bunch of them. Since the purchase, I noticed at least one explosion related to this brand of cells when used in series. A previous question about using these cells in single cell lights went unanswered. I really like this light format, and would like to be able to obtain cells at reasonable cost, but if there is any potential danger, I would be quick to recycle these things and buy something higher quality.

Thanks in advance!

 

[moldyoldy]

Do you remember the specific brand of CR123 primary that caused the problem?

I have only used Duracell, Energizer, and Surefire CR123, and 100% of my current inventory is Surefire. However, lately I have been getting into single-cell CR2 lights, and, upon reading many positive comments about a particular brand of first-tier Chinese made cell, bought a bunch of them. Since the purchase, I noticed at least one explosion related to this brand of cells when used in series. A previous question about using these cells in single cell lights went unanswered. I really like this light format, and would like to be able to obtain cells at reasonable cost, but if there is any potential danger, I would be quick to recycle these things and buy something higher quality.

Thanks in advance!

ummmmm, I would rather not cite the specific brand. Production of that brand for the US Market may have improved since the event over a year ago. I have used Surefire, Panasonic, Streamlight and Titanium Innovations with no problems. For my few remaining purchases of the primary CR123 cells, Titanium Innovations has been my choice. Why did I settle on this cell? Because of the PTC protection - essentially a thermal fuse set somewhere around 5A. Has anyone tripped the PTC protection? Yes - a few cells in either a 1x or 2x CR123 light. I cannot prove very much since I was called after the fact when there was no light at all. I replaced the CR123 cells and suggested an eventual changeover to AA or 18650 format. my last holdout now has an EA4 and two 18650 lights. so far, so good.

As for CR123 cells, take note of the changing marketplace. to my visibility, CR123 cells are fading from dealers, especially the rechargeable format of Li-Ion or LiMN, etc. In my experience, the lower runtime in currently available lights at a reasonable output is less than 30 min - too low to bother with. either 18650 or some number of AA cells, typically 4x (EA4, D40, etc). These people are not flashaholics, they use their lights, often at full brightness or maybe a notch down from full brightness if the light gets hot.

 

[BillSWPA]

ummmmm, I would rather not cite the specific brand. Production of that brand for the US Market may have improved since the event over a year ago. I have used Surefire, Panasonic, Streamlight and Titanium Innovations with no problems. For my few remaining purchases of the primary CR123 cells, Titanium Innovations has been my choice. Why did I settle on this cell? Because of the PTC protection - essentially a thermal fuse set somewhere around 5A. Has anyone tripped the PTC protection? Yes - a few cells in either a 1x or 2x CR123 light. I cannot prove very much since I was called after the fact when there was no light at all. I replaced the CR123 cells and suggested an eventual changeover to AA or 18650 format. my last holdout now has an EA4 and two 18650 lights. so far, so good.

As for CR123 cells, take note of the changing marketplace. to my visibility, CR123 cells are fading from dealers, especially the rechargeable format of Li-Ion or LiMN, etc. In my experience, the lower runtime in currently available lights at a reasonable output is less than 30 min - too low to bother with. either 18650 or some number of AA cells, typically 4x (EA4, D40, etc). These people are not flashaholics, they use their lights, often at full brightness or maybe a notch down from full brightness if the light gets hot.

Titanium Innovations is the particular brand of CR2 that I purchased. Glad you have confidence in them. Part of my thinking has been that less can go wrong in a single cell light, but your earlier post called that theory into question, which I why I wanted to check.