Venting/exploding li-ions in flashlights where the threads and o-rings make an air-tight seal are a lethal combination because the the pressure builds up to extreme levels. When enough pressure builds up, the aluminium (or SS or titanium) fragments can seriously injure the user and damage property (analogous to a grenade), as well as lung damage caused by toxic fumes (hydroflouric acid from electrolytes, see the L2P explosion).
I’m sure we’re all aware of the dangers (as well as benefits) that li-ion cells bring, so please take care when handling them, especially in flashlights or other air-tight environments.
Charging issue in my book: 0v cells should not have charged. A good charger knows better. (btw these were Sony high-drain cells) 8s1p w/ half the cells dead and a 250w filament is effectively a dead short reverse charging 4s Li-Ion off of 4s Li-Ion.
Not Li-Ion. I don’t think this illustrates the danger of cheap Li-Ion any more than it demonstrates the danger of any other decent density primary or rechargeable chemistry. These were name brand primary cells…
I should have been much more clear: single cell LiCo setups is what I was referring to. Multi-cell setups can end up with some cells charging or reverse charging other cells. My mistake for not specifying that, sorry. You just cannot make this happen in a 1s1p light.
I do think Paul’s case illustrates really well what happens when the majority of protection PCBs should come into play: nothing. They do not protection anything.
Why are you ignoring multi cell series lights?
Normal brick&mortar stores are starting to sell multi cell li-ion lights.
Neither you nor I can know that.
Have you seen that teardown of a cheap 18650 posted not long ago. It had no CID, no PTC. In the event of a short the only thing it can do is heat up until it vents or runs out of energy. In a quality cell either the PTC would intervene then reset after the cell cooled or the CID would trip (which doesn’t reset). Some cheap li-ions are even sold & labeled as “protected” without any protection circuit.
This is just a way to provoke the cell into venting. Being unable to accept the charge the energy produces internal heating until thermal runaway is reached. You could also accomplish it wrapping the 18650 with nichrome wire.
The danger of cheap batteries is that they do not always have any safety features. Since they are cutting corners on safety the quality control during manufacture is likely to be poor as well. The chance of catastrophic failure is much higher. Even quality major brand li-ions have had catastrophic failures.
In the end, the point of a 18650 in flashlight thermal runaway video is just to show the potential. Many people seems to have short attention spans. Some don’t like to read or are stubborn. A video gets the point out there. Junk li-ion battery + flashlight can be a pipe bømb.
Wires can enter through the front. Remove led, wires enter through reflector led opening, seal with epoxy.
No one knows what the rate is for junk batteries. As with most things many failures will go unreported & of those that are reported only some will make their way to us.
Fair enough on both counts in your reply to my comments. I do feel that the risks of these cheap cells are generally overstated - but I certainly do not want people to go uninformed. I recognize that I do get too defensive about rechargeable lithium chemistry risks. Sometimes to the point where I get worked up and overlook or ignore important things just to make a point.
I’m not sure that making people aware of the dangers is going to be a boon to society.
Even with that in mind, it seems that there have been very close to zero cases that we’ve heard about. That list of “3” earlier was pretty scrappy.
The real solution to this “dangerous” situation is to stop other people from doing what we are doing. Individually charging cells? Really? Monitoring cell health yourself? Really? Direct drive lights? Per-cell safety mechanisms taped onto the ends and then stacking the cells? Sealed flashlights full of batteries with no burst disk or similar built into the design? As was mentioned probably over and over in the TK Monster thread linked above, lights like the TK Monster are just begging to eviscerate someone on failure.
Who’s going to make the call though? Imagine if laptop or cellphone manufacturers had arrived at the scene after the hobbyists had already showed up with tons of cheap, unreliable chargers, boxes full of used cells, and no battery management circuitry! I think that’s a fair way to look at the current situation. I think it would be hard for Fenix or someone to make the call and say “OK, packs only. All with BMS. We’ll also add reporting faculties to our lights and chargers to better inform you of pack health as determined by the BMS.” and do well in the market right now.
In other words, as I see it, if there is a problem… just informing people that cells can vent and cause a flashlight to explode is really the tip of the iceberg. There I going off all half-cocked again. Take my words with a grain of salt.
Junks batteries & junk chargers are the things we should strongly advise people against IMO. With a good charger & quality cells the risks should be small. But with junk, who knows.
I see too many people on BLF who think the cheapest junk AC powered li-ion chargers available are just fine. Worse is that few correct them. Instead other join in and say “Have one too. Not problems yet.” Plus you know some will leave those chargers unattended at times. Sometimes people do comment that they’ve had cheap chargers stop working, pop, burn or smoke.
Are you more likely to die in a car crash? Hell, yeah. But a halfway decent charger costs what, $6-10?
But I digress.
A video of a flashlight blowing apart will get views. Maybe some people will reconsider using the cheapest batteries & chargers they can find.
I’d just like to point out that I don’t hope to get many views, that’s not my intention. All of my videos are unlisted and cannot be viewed without direct links.
Although this is a budget light forum, I’d just like people to think twice about using cheap batteries and chargers to prevent tragedies from happening. Whether one values saving a few $$ on cheaper batteries and chargers at the risk (albit very small) of a fire or explosions is something to think about.
Do one just hooking to a straight 5vdc USB 1A source…then leave it on…like someone plugging in a flashlight with direct feed on one of those 5vdc wall warts
See just how long it takes to go kablooey if it does…real world “what would happen if someone who didn’t know did that” kind of test
It’s a dirty job. I’m thinking that you can take a LiCo cell up to 5v and just leave it there. That’s effectively what would happen here I think, w/ a few mA being burned off constantly as heat. I don’t think it would ever vent just from that, but if it did I suspect that you’d wait a couple of eternities to see it. That makes it a very difficult test for us hobbyists to run safely.
It’s easy to do the short version (just hook it up for a few hours while you are outside reading or whatever), but if it doesn’t fail immediately then what? I guess you could cycle it like that….
Take my words with a grain of salt.
