I have noticed over the last year that my NCR18650B batteries are getting weird marks on some of the batteries.
I ignored it at first but its been bugging me, id rather be safe so I figured Id ask here.
EDIT: These particular batteries have been used for a CBD herb vaporizer as well as flashlights.
The device gets quite hot, could the heat be responsible for the markings on the battery?
They look like they are under the wrapping.
Looks like humidity.
hmmm that is odd, I do live in the UK but Its not THAT bad here.
I havent even used these outdoors before.
Do you think they are they still safe to use?
EDIT: These particular batteries have been used for a CBD herb vaporizer as well as flashlights.
The device gets quite hot, could the heat be responsible for the markings on the battery?
They look like they are under the wrapping.
Shift the wrapping, if the colouration changes like you expect water to and comes back then you know.
yes, when I run my fingernail over the markings with a bit of force they smooth out and blend together.
EDIT:
Actually, one of them had a broken sleeve so I stripped it just now and there was nothing on the wrapper, or on the battery after I took it off, it just disappeared.
So then I think there shouldn’t be anything to worry about.
Although, on that note, I dont think this battery is worth rewrapping…
That is most likely rust. Which is caused by water.
Looks like they are either rusting or leaking under the wraps — Do they have a funny smell or do they smell like rust iron
I’d unwrap one and see what’s going on —- Rust will be evident —leaking will be coming from the end
Lol probably, ive pretty much dedicated these to my herb vaporizer now so my flashlights get their own cells.
No funny smells.
I did unwrap one and as soon as i did the markings went away. There was nothing visable on the battery itself or the inside of the wrapping.
So it might just be moisture that somehow is getting under the wrapper.
I would be careful, the vape is right in your face. If a battery fails catastrophically, it would be bad.
First of all, this does not look good. Second and I am surprised no one asked, how do you know they are genuine NCR18650B? Where did you get them from? Name brand batteries are copied more than $100 bills. May be a crapfire underneath.
It seems fairly obvious to me the cells are getting so hot during vaping the outside of the wrapper is getting cooked… thus creating the “blemish” on the outside of the wrapper.
My opinion, others may vary. 
May not be related… and I’m also not a vaper, so my assumptions might not be correct…
Assuming those are genuine NCR18650B — these are low-drain batteries (rated up to 5 Amps continuous discharge charge).
Does vaping use more than constant 5 Amps? This might be a reason why the batteries get hot — because the NCR18650B’s discharge current is not able to handle the higher power drain on the vape device…
As ShyOne mentioned above, the vape could have been pushing the batteries much harder than they are rated for, thus the reason for getting too hot. (batteries will normally get hot while in use, but not “too hot”…
The NCR18650B is a perfectly fine cell provided that it's genuine and it's used within the manufacturer's power ratings (< 6A).
With that being said, I wouldn't use them for vaping. You're probably running them at > 15W and that's causing them to get cooked.
I had similar looking cells (probably 8+ old, LGs). All had capacity loses or issues with endless charging - cells weren’t able to go above 4,1-4,2V and got very hot during charge (80C+). Don’t know when Liitokala temp. protection kicks in, but looks like not soon enough.
There were very little moisture under the wrap, no strong smell, but all had bigger or smaller corrosion signs similar like here.
Cells were never used in high power flashlights, my old Solarforce drains <3A on turbo and I almost never used it above 60%.
