I assume dropping an 18650 li ion onto carpet won’t do any harm, but what about on laminate or hardwood flooring? How about on concrete, or onto concrete from more then 4ft?
It’s not so much the drop or what it hits etc
The important thing is, how is the cell, if it’s metal casing is damaged or deformed in any way, I’d probably recycle it.
I guess its probably more critical on a protected cell, as you could damage the chip and maybe not know it until it didn’t work when you really need it too.
depends on at the particular cell.some have thicker can,better seperator,ect.
too many variables.just dont drop them!
ul recognised(thats the backwards ur symbol) cells have a drop test penetration test,ect spec.
ul pdf
I can’t speak to the actual safety of the batteries, but I use batteries that have dropped from 1.5m (4.5ft) onto hard tiles without thinking twice. If the casing has no dents, I will probably use it.
I’ve read that a casing puncture is a sure fire way for these batteries to ignite/catch fire . (no pun intended lol.)
After a drop, I’d carefully check them for unusual temperature increase and while wearing eye protection inspect them closely for damage.
Wasn’t here anywhere a torture test of batteries…?
I am more concerned about dropping them while charging and insertion/removal from flashlights
I know this isn’t what you asked Bort, but I damaged a Duraloop’s casing significantly without any noticeable effect on performance. I was checking fitment of a pair of cells in a 4ft copper pipe and they got stuck at the end. I should have just poked them out, but instead I banged the pipe on the hard floor until things came loose - and went flying down the length of the pipe. The bottom of the bottom cell was significantly crumpled and it continues to operate. It appears to be just fine, performance-wise. It just won’t fit in skinny battery tubes.
While that is a NiMH cell, my understanding is that actual construction is similar for both chemistries. I speculate that under other circumstances I could have ended up with a shorted, non-functional NiMH or a shorted, CID-tripped, non-functional Li-Ion. [EDIT: or a shorted, very very unhappy Li-Ion!]
I’d think that the CID should protect you from all internal shorts in 1s1p scenarios (high voltage scenarios have been proven to defeat this mechanism). What the CID will not protect you from is an actual rupture of the can (or bag, or vessel, or whatever) of the battery. My damaged Duraloop was all smooth bends, so hypothetically if it was a Li-ion I don’t think I’d be overly concerned about metal fatigue. Any sharp bends are definite trouble in my book. At the end of the day though, if I had a Li-Ion which looked like that… I think I’d recycle it.
Also, that damage was at the bottom of the cell. Damage at the top of the cell, near the positive contact, could affect the operation of the CID or PTC - definitely a very bad thing as those are integral safety features of these cells.
EDIT: see Halo…’s post #9 below for the reasoning behind the strike-through.
Very interesting, thanks for posting that experience, i drop eneloops and duraloops all the time, i even dropped one outside and it was on the lawn a while last year.
CID does not protect from internal shorts. It only disconnects the internal positive connection from the external positive terminal / button.
Hmm, good point. My best defense is that I’m pretty tired. I guess I shouldn’t post safety advice while fatigued… but I don’t guarantee that I wouldn’t have made the same mistake while sharp & alert.
I’ll add some strike-through where appropriate.
i had the same thought, how would it know there were shorts in the battery, there is no internal short sensor that i know of but i didn’t say anything because i thought i don’t know much about the CID or PTC in the cell so maybe i didn’t know enough
Always difficult when tired.
Mistakes or confusion about li-ion protection devices seem common anyway.
Both the PTC and CID operate in a very straightforward way, there should be nothing to be confused about there. Yet I still screwed it up. 
With that out of the way: Your statement applies just as well to almost every area of human knowledge… 
Safety Instructions for 18650 batteries
www.katogroup.eu/safety-instructions-18650.aspx
(my emphasis added)
What to do with a (possibly) defective lithium-ion battery
If in doubt as to the state of a lithium-ion battery because you have dropped it, for instance, or when you know it is damaged, you should take the following steps:
- Treat the battery as a potentially explosive object. Make sure that you use at least safety goggles and protective gloves to protect yourself.
- Store the battery in a safe, dry place, away from highly flammable materials or products.
Leave it there for at least one hour in case there is a short circuit and the battery starts heating up.
- Check to see if the battery has become hot. If so, leave the battery until it has cooled off.
- For further protection, wrap the battery in a piece of kitchen paper and seal it with sellotape.
- Put the battery into a box and label it, Lithium-Ion battery. Hand it in to a chemical waste disposal facility.
Someone from the Netherlands may translate “kitchen paper” — I’m guessing aluminum foil?
Heh, I assume they are actually referring to paper towels. Aluminum foil sounds like a bad idea.
EDIT: https://www.google.com/search?q=laag+keukenrol&es_sm=93&source=lnms&tbm=isch&sa=X