^
And another one of my points is that you totally disregard that these are RELATIVELY NEW cells and OTHERS happen to share my belief and experience w/ L. ion CELLS!!!
HERE ARE 2 EXAMPLES!
1. Fresher cells, not beat upon, shouldn’t be at 4.14v after 8 hours on a good charger, is my thought on the matter.
2. My cells that are charged to near 4.2v tend to rest no lower then 4.18v(range of my cells).
OK,WHAT IS ALL THE HUB HUB ABOUT!!! 
Ok,I started another test for BOTH batteries on February 9th, 2017.
BOTH BATTERIES CAME OFF THE CHARGER @ 4.20V.
AFTER RESTING FOR 1 WEEK:
BATTERY “A” WAS @ 4.18V
BATTERY “B” WAS @ 4.17V
These are certainly Acceptable and Normal voltages 1 Week after being charged! 
I am not sure why my first test had the voltage DROP from 4.20V TO 4.14V IN 8 HOURS!
I believe my cells are Fine, they are real and they should perform and last like my other VTC cells have!
Why would invest in this if no flashlight demands such high level current? Is not NCR18650GA sufficient for all?
I believe my single cell “Modded” lights benefit from a VTC6/30Q over a “GA”.
That is what I was told by the guy who modded them, so I use them.
For direct drive lights (like those that use a FET driver) the lower IR of high drain cells increases performance, even if the resulting current draw is not very high. For example, you might get 6A with a high drain cell and a single XPL but only 5A with the GA. In this case it is not a large increase in performance, but an increase nonetheless.
Also, some modded flashlights do demand >15A current from a single cell.
Thank you. Nice response.
I see all the 80°c ratings on this cell and was wondering, I’ve got a project going into my roof is probably 60-70°c max in summer (Australia) I checked today with IR thermometer it was 55. I’ve been researching what battery to use, the best I’ve got is an lgaahd2c1865 which says it’s rated discharge temperature is 70°C in the data sheet, that one’s from a dyson vacuum battery pack. All my other cells I could find data sheets for were only rated for 60°C.
My question is I’ve basically got 150uA continuous standby current and maximum 1a draw for maximum 10s once triggered, given your experience heating cells for fun do you think I’ll have problems with my single cell venting in my roof. Do you know of any high temperature tested cells other than this one? Any thoughts on long term operation of cells in high temperature… I imagine it will degrade capacity faster. Appreciate your input!
Officially I would not recommend it, if it is a small project, you might consider using some eveloop AA cells instead.
Un-offically I leave some flashlights with cells in my car all year round and it can get up to ~120-140f in the summer in there. I have not had any issues and they hardly even self-discharge. I generally charge them once a year and they are normally still above 4V if I did not use them.
Cheers Texas, I did think about that but eneloops are only rated for 50°c and as it’s my electronics design… It won’t work well off 2 AAs, low battery alarm kicks in at 3.1v, and I can’t use any buck/boost for the standby as it took me ages just to get the standby current that low, I’d never get close to it with a dc-dc converter. What’s the worst that could happen, with a high quality cell it’ll just vent and I’ll have a dead battery… Probably. I’m hoping someone might have some tips for higher temperature rated or safer chemistry but still 3.7v nominal battery…
could you run 3x AA cells? It would only be 0.3V higher charged voltage.
If you put the cell in some kind of metal case that would protect any fire from escaping yet not turn into a pipe bomb, then I suppose it could work, really depends on your attic and how flammable it is.
I would basically plan on the cell venting, if you would not feel safe with it actively venting, then I would not use it.
I could but I'm not certain how much safer would really be. Given the rated temperatures on the cells, I would definitely exceed the ratings on the eneloops but I would not exceed the rating for the vtc6 or the Samsung 25s /25r, I would probably not exceed the rating for my lg cell (70°c). I had a bit of a fish around for data on eneloops behaviour at elevated temperature but couldn't find anything. Lions however I found this paper which shows thermal runway onset temperature for various charge states, cells that are not overcharged all went into thermal runway over 140°c which leads me to believe the data sheet. Unfortunately they didn't actually state which cell they tested.
Like I said I think you will be fine with the 18650 cells, I would just build it to handle a possible venting.
Sorry for necroing…
I just got two VTC6 that measure internal resistance of 47 and 67 mOhm on 1a discharge in my MC3000 charger. From what I read here it should be <<40mOhm. Did I get second-grade cells?
Update: Looks like MC3000 only measures IR in the beginning of the cycle. After dropping 400mAh, I restarted discharge and it measured 30 and 43 mOhm already. Does it make sense?
Yes. Battery chargers actually don’t measure Internal resistance correctly.
Yes, but it do not eliminate problems with contact resistance.
You mean resistance of the charger terminals?
After some more tests, it behaves as follows - I place VTC6 in, say 1st, slot. Start discharge. MC3000 measures IR about 50mOhms. About 200mA down, I restart the discharge program. MC3000 measures the IR again on start and now it’s down 5-7mOhms. Eventually when the battery was about 3.9v, IR stabilized at ~30mOhs, which is what is reported in the beginning of this thread.
So does IR changes (decreases) with discharge? Again, I was not touching battery/charger in that experiment - only stopped/started discharge program through the app.
HJK, I have read your IR measuring post [1] and it made me even more puzzled - you say IR increases as capacity drops, but I see the opposite. Unless it’s the temperature rise, which I doubt, since it was 1A discharge for ~30 minutes total and the battery was cold to touch (room temperature).
Ideas?
IR do not increase before the battery is nearly empty, here is a curve from another battery:
