What's the consensus on Lithium Ion batteries?

I'm a noob. I've been dreaming of getting an 18650 powered flashlight since last year but could not justify spending more than $10. I saw a deal last week on a Fenix TK11 I could not passed up. I did my due research on lithium powered flashlights and found out the dangers that plague lithium batteries. I was surprised. I thought this would be an easy decision. Now I'm having second thoughts of getting the Fenix TK11. Such a nice light. I was thinking of giving it as a present.

I did a lot of research on the topic of exploding lithium ions and I'm more worried now than ever. I may have to stick with AA batteries. I do not want someone injured by a gift because I didn't heed the dangers and passed on a pipe bomb to an unsuspecting recipient. Am I justified to be paranoid or am I only getting one side of the story? How widespread or prevalent are exploding lithium ion batteries relative to nimh batteries? I understand that even nimh batteries can explode but it never made it on primetime news. I do remember the laptop battery fiasco a few years ago. Are lithium ion batteries inherently more dangerous than nimh batteries? As I understand it the main cause of the explosions are internal shorts, whether artificially induced or naturally occurs, that overheats the cells causing catastrophic chain of events. Overcharging produces the same effect.

Now, I've had more than ten nimh batteries develop shorts despite my utmost care. They leak and self discharge within a few days. They never explode fortunately. If these shorts can happen to lithium ion batteries just as easily then I am certain to encounter an explosion eventually. I want to hear if there's another side to the story. Just what are my odds?

Explosions are extremely rare and more often happen on lithium primaries when batteries are abused as in multi-battery set ups when one battery is significantly more discharged than the other. This sets up a reverse charge situation and then they can explode but only in an airtight light.

This whole run of situations is such a small chance and almost doesn't apply to the TK11 running 18650. For one you can't reverse charge a single cell, you can only kill it. The worst that happens is on the subsequent recharge, when it's in the charger it vents possibly with flame but that's extremely unlikely. To prevent this from happening you should get protected cells. And also get a quality charger with true termination cut-off to prevent overcharging.

You're not going to dangerously discharge these because in a single cell light there are multiple safety nets. First of all the Fenix light has a low voltage warning, when the voltage gets low on one cell the light won't even function but the cell should still be fine, and as a last resort the protection circuit will kick in. The protection circuit even protects from accidental short circuits. So a protected 18650 in a quality flashlight I'd say is even safer than multi-cell nimh for the most part.

Some Energizer batteries, especially the 2500s, were notorious for failing prematurely due to internal shorts.

That said, I am not sure I would give a lithium ion powered light to someone as a gift unless they were an enthusiast. Lithium ion cells really do need a little more care and attention to detail than ordinary NiMH cells, and unless they are used by someone with knowledge of what they are and how to care for them, they can be considered dangerous.

There are some very nice lights that take AA cells, and those would probably be more suitable as an introduction to advanced flashlights.

Normal lithium cobalt cells are unstable by design and if you use unprotected or bad quality no-name cells you might be in for a nasty surprise.

If you want to be relatively safe, use AW's black label LiCo cells with protection circuits. If you want to be completely safe, use AW's IMR LiMn cells. Lithium manganese is a safe chemistry unlike LiCo.

Still, rechargeable lithium might be strictly an enthusiast's domain. The cautions to not discharge cells completely lest you ruin their capacity entirely might be confusing and/or intimidating.

AA light + Eneloops should be a good bet :tinfoil:

I try to think of it as this. If the person is intelligent enough to use power tools, which a lot of them come with li-ion batteries, they're knowledgeable enough to use a single cell light. Actually I think the lithium packs for power tools is slightly more dangerous as the contacts are so close together and are easier to short. What scares me is the multi-cell power tool batteries don't seem to have a balancing circuit, yet they seem to operate just fine.

qwertyydude said:

I try to think of it as this. If the person is intelligent enough to use power tools, which a lot of them come with li-ion batteries, they're knowledgeable enough to use a single cell light. Actually I think the lithium packs for power tools is slightly more dangerous as the contacts are so close together and are easier to short. What scares me is the multi-cell power tool batteries don't seem to have a balancing circuit, yet they seem to operate just fine.

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AFAIK due to the high current draws power tool battery packs usually contain LiMn cells, which are 'safe' as opposed to LiCo.

qwertyydude said:

I try to think of it as this. If the person is intelligent enough to use power tools, which a lot of them come with li-ion batteries, they're knowledgeable enough to use a single cell light.

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Personally I don't find that analogy fits, because with very few exceptions, light manufacturers tend not to be also the supplier of cell(s) and chargers. In short, they (Fenix, EagleTac, ITP, Olight, Sunwayman, etc) are not full systems integrators.

A power tool maker is a systems integrator, responsible for the product at every level. Even if they don't produce all components within their product, they are the ones who bring it all together, with input from engineering, production, QA, safety, and support. Most often all these components require rigorous testing to meet various standards agency approval, and on top of all of this, the tool / cell pack / and charger all carry the makers name. Tool makers crave reliability and repeatability and they get it because they have volume.

Contrast that to the speciality flashlight industry where the enthusiast is the ultimately the systems integrator, more often than not buying components from varied sources, components which may be different from batch to batch, order to order. Is the XYZ Model II charger you buy today the same as someone else bought last week? Might not be.

If my Makita|DeWalt|etc li-ion powered hammer drill blows up while in use or burns down the kitchen I built while its pack is charging, I'll be going after Makita, not one tool maker here, a Pila or UF charger there, a cell packager there. Makita is fully aware of their responsibility and can produce a consumer-safe product because they know everything about every component in their tool system and can design a pack with safety features (a must for tools that can and do get dropped), design a tool which doesn't over-discharge or unsafely discharge the pack, and a charger which properly and safely recharges the pack. There is no finger pointing among suppliers, it is Makita's name on the line.

Mr Happy said:

That said, I am not sure I would give a lithium ion powered light to someone as a gift unless they were an enthusiast. Lithium ion cells really do need a little more care and attention to detail than ordinary NiMH cells...

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Two thumbs up.

When 18650 sized cells with appropriate characteristics are available at any corner store, then we'll know it is safe to give an 18650 powered light as a gift to the average user. The bottom line is li-ion rechargeable cells are really not consumer items at all, they are designed to be used by systems integrators.

I don't want that responsibility hanging over my head if I am giving a gift. A nice 1 or 2 AA light would be a much better choice and the output will still blow anyone away (in a nice way) that isn't already a plugged-in enthusiast.

pinoy said:

I'm a noob. I've been dreaming of getting an 18650 powered flashlight since last year ... I did my due research on lithium powered flashlights and found out the dangers that plague lithium batteries. I was surprised. I thought this would be an easy decision. Now I'm having second thoughts of getting the Fenix TK11. Such a nice light. I was thinking of giving it as a present.

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... and a high five to you. Your reservations are well founded, particularly for a light system meant as a gift.

However in your own hands, given you've taken the time to do some research, clearly you are an individual that could responsibly use such a building block in your own lights. As long as we don't forget that the responsibility for designing (buying) a safe "system" (light, cells, charger, method of use) is ours, we should feel comfortable using these components as the great tools they can be.

I avoid LIon cells wherever possible. I'm not concerned about their safety -- for me they are a fragile, short lived solution to a problem that I don't have. LIon holds about the same amount of power as NiMH when compared by volume. The tiny savings in weight offered by LIon Is canceled out for me by the fact that they begin to deteriorate the moment they come off the assembly line whether they are on a warehouse shelf, in a store or being used. In contrast, I just dumped a set of NiMH cells that I got eight years of service from.

The shorter charge times are nice but has little impact in any of my real world applications.

While I'm sure that there are great uses for LIons (just as there are for every other battery type) I think that they provide very little actual benefit in most of their current applications.

Sub_Umbra said:

While I'm sure that there are great uses for LIons (just as there are for every other battery type) I think that they provide very little actual benefit in most of their current applications.

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I think the single 18650 light is probably a nice form factor with the potential for high brightness and long run time.

qwertyydude said:

Explosions are extremely rare and more often happen on lithium primaries when batteries are abused as in multi-battery set ups when one battery is significantly more discharged than the other. This sets up a reverse charge situation and then they can explode but only in an airtight light.

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Can someone explain this to me? They can only explode when in an airtight flashlight?

I remember reading a news story last year about a police officer whose flashlight exploded in his hand. This was easier to understand as his flashlight was made of plastic and the plastic didn't stand a chance against the chemicals inside the 18650. I was therefore wondering if an all-metal flashlight like the Fenix TK30 could indeed become a pipe bomb. I always figured that the metal tube would offer some protection but now I'm not so sure. Some people are making it sound as if these 18650 batteries have some dynamite in them. Could the batteries inside a TK30 really blow the flashlight up and send shards of metal flying everywhere?

Pipe bomb? Really?

DVN said:

Pipe bomb? Really?

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Yes: confinement makes explosions. A battery in the open air may just burst into flames, but put that same battery inside a metal tube and you can have a significant bang with parts flying everywhere and injury to persons and property.

When you put an energetic battery like a lithium ion or primary lithium inside a sealed metal tube, you do indeed have a potential pipe bomb waiting for a trigger. Such events may be rare, but the potential is always there.

The main difference between a battery and a stick of dynamite is that the dynamite is designed to release its energy all at once, whereas a battery is designed to release its energy in a controlled flow. But the total energy in a battery, weight for weight, could be as much as 25% of the energy in an explosive like gunpowder or TNT. If you let that energy out all at once, a thin metal tube is not going to provide any safety.

DVN said:

Could the batteries inside a TK30 really blow the flashlight up and send shards of metal flying everywhere?

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Put gunpowder on the ground and light it, it hisses as it burns. Put it in a bullet and BANG! It's all about how fast the energy builds up and how it gets released.

It's actually very difficult to get a metal tube to explode into separate bits and create shrapnel going every direction. Shrapnel weapons use pieces that are already separate. It's even more difficult if the pressure builds slowly as it would from a battery.

What's really going to happen is the weak point of the light is going to fail. That might be the rubber in the tailcap, might be the front lens, might be some threads somewhere. You might even get a split in the tube. There could be a substantial POP as something lets go, and a small amount of shrapnel, especially if the lens goes. This may be followed, immediately or soon after, by flames shooting out the new hole in the light.

The violence of the 'explosion' is determined by how much pressure the light can hold before letting go and how much air volume was in the light before things went wrong.

It won't kill bystanders, but it might f___ up your day!

DVN said:

Pipe bomb? Really?

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Here's a thread on CPF with links to a thread discussing one such incident in some detail, with pictures and real blood. And his coffee maker didn't fare too well either!

In my mind it doesn't matter too much what the specifics are - protected cell or abused cell or not - the important point to be aware of is that lithium based rechargeables pack a ton of energy into a small space and if that energy does get released all at once, whatever the cause, really bad things can happen.

Knowing that, we can manage the risk with good equipment choices and by following straightforward best practice in using the cells and gear.

tandem said:

Here's a thread on CPF with links to a thread discussing one such incident in some detail, with pictures and real blood. And his coffee maker didn't fare too well either!

In my mind it doesn't matter too much what the specifics are - protected cell or abused cell or not - the important point to be aware of is that lithium based rechargeables pack a ton of energy into a small space and if that energy does get released all at once, whatever the cause, really bad things can happen.

Knowing that, we can manage the risk with good equipment choices and by following straightforward best practice in using the cells and gear.

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I was actually reading that thread earlier. In that case though, the tail-cap of the flashlight blew off which is different from the metal casing itself fracturing into small pieces. I can understand the tail-cap being blown clean off the body.

DVN said:

I was actually reading that thread earlier. In that case though, the tail-cap of the flashlight blew off which is different from the metal casing itself fracturing into small pieces. I can understand the tail-cap being blown clean off the body.

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In terms of potential harm to persons or property, I think the difference is somewhat academic...

DIWdiver said:

What's really going to happen is the weak point of the light is going to fail. That might be the rubber in the tailcap, might be the front lens, might be some threads somewhere. You might even get a split in the tube. There could be a substantial POP as something lets go, and a small amount of shrapnel, especially if the lens goes. This may be followed, immediately or soon after, by flames shooting out the new hole in the light.



The violence of the 'explosion' is determined by how much pressure the light can hold before letting go and how much air volume was in the light before things went wrong.

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This.

That's what I previously believed, that the weakest point on the flashlight would fail and that the pressure from the gases released by a faulty 18650 would escape. But after reading lots of threads, I started getting confused and thought that the "leaky/faulty" reaction within the 18650 battery was instantaneous and thus would create a dynamite-like effect. That it could just blow up while sitting on my desk. That's why I was starting to look at my spare 18650 batteries out of the corner of my eye...

Rather, if I'm understanding correctly, the faulty battery will over time release gases and pressurize the battery tube until a fail-limit is reached. So now I understand why the air-tight environment is necessary. An 18650 might burn and release gases outside but it won't explode. If confined to a battery tube, the pressure can cause the explosion? Is this right then?

Thanks for the info guys.

Well a pissed-off battery can certainly eject its guts with some force, but it does sound like the worst explosions are from the sealed tubes. I'm surprised the rubber boot on the switch doesn't blow out well before the body ruptures, though. Must not be easy airflow from the battery chamber to the switch.

I'm not a real fan of all these "macho looking" aluminum lights, but I guess they're easier to make than custom plastics with just enough metal for the heatsink. Either that or a lot of casual users like to pretend they'll be on a tactical assault team one of these days

DVN said:

That's what I previously believed, that the weakest point on the flashlight would fail and that the pressure from the gases released by a faulty 18650 would escape. But after reading lots of threads, I started getting confused and thought that the "leaky/faulty" reaction within the 18650 battery was instantaneous and thus would create a dynamite-like effect. That it could just blow up while sitting on my desk. That's why I was starting to look at my spare 18650 batteries out of the corner of my eye...

Rather, if I'm understanding correctly, the faulty battery will over time release gases and pressurize the battery tube until a fail-limit is reached. So now I understand why the air-tight environment is necessary. An 18650 might burn and release gases outside but it won't explode. If confined to a battery tube, the pressure can cause the explosion? Is this right then?

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Speed is relative. If a lithium ion cell starts to go, you don't have any time to take corrective action.

Take a look at this demonstration and then imagine these explosions being confined inside a sealed metal tube:

http://www.youtube.com/watch?v=jjAtBiTSsKY

The demonstration involves the same kind of cylindrical cells used in flashlights. Note the flames. You really do not want to experience a lithium ion cell venting with flame inside (or outside) a flashlight tube while you are close to it.

A properly cared for, properly charged and properly used lithium ion cell is unlikely to get out of shape like this, but in the wrong circumstances it can, and it can really ruin your day.

I would never consider gifting a light that used li-ion cells unless I knew the recipient already used li-ion cells in flashlights.

With few exceptions, gift flashlights to non-flashaholics should almost always use AA or AAA cells. That's my opinion, at least.

--flatline

flatline said:

I would never consider gifting a light that used li-ion cells unless I knew the recipient already used li-ion cells in flashlights.

With few exceptions, gift flashlights to non-flashaholics should almost always use AA or AAA cells. That's my opinion, at least.

--flatline

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+1

But for my own personal use, I rather like and enjoy using li-ion batteries in flashlights, among other things. Especially 18650's. As Mr. Happy indicated, they can be a great form factor that can provide great brightness and long runtimes. To me they are like an AA on steroids. Eneloops have their place (uses) in my arsenal, but so do Li-ions.