Hmm, everytime I’ve ran a light to low voltage cut-out the Panasonics have run for significantly longer than the Sanyos I also tested. I can’t remember all I have tested but certainly the C8 XinTD sticks in my memory, around 15min extra (on 3100s aswell)!!!
Has anybody else tested or is everyone going by HKJs tests?
Edit, just checked my old review, the Panasonics ran 22minutes longer than the Sanyo, maybe a light meter would show a difference otherwise niether looked brighter throughout. XinTD
NCR18650B is the easy choice for me!
Basically all my lights are driven hard on high. Obviously, high output is the goal, but when you have high output you get low runtime. The Panasonic cells give me the best of both worlds, high output for the majority of the time when I use them, and long runtime the few times I need long runtime.
In single cell lights I normally charge the batteries when they get used near the halfway point. And when I don’t charge them, or have the ability to charge them, I like knowing that I have a battery that lasts as long as possible.
Modified throwers like ZY-T08, ZYT619 (single cell, or parallel setup) are examples where where you want higher vf in order to achieve the maximum light output.
On the opposite, take a modified thrower like the ZY-T13. It will stay regulated throughout the whole range. vf is no issue, but then the capacity of the Panasonics can come handy.
The only place I find the Sanyo batteries better are in terms of price and output when there is about 40% or less capacity left in them. I value max output and runtime. The Panasonic batteries wins in both departments.
I have tested the mentioned Sanyo vs Panasonics (both protected) with a few drivers. In some cases with fairly fresh batteries sometimes the Sanyo will only output 2,5-3amps. While the Panasonics will do 3-3,5… I have even seen 0,7A+ higher current at startup with the Panasonics compared to the Sanyo.
Yea it’s very possible/likely the panasonics dropped out of regulation earlier but still lasted longer. In the end I still use 3400s most of the time except for high current lights or my nichia high Vf lights.
For Average current use (up to 3A): Panasonic NCR18650B (better capacity).
For High current use (up to 6A+): Panasonic NCR18650PD (better run Voltage/capacity, longer cycle life).
Here’s a comparison of some cells at 3A:
http://www.dampfakkus.de/akkuvergleich.php?akku1=141&akku2=122&akku3=103&akku4=99&akku5=&akku6=&a=3
And the same at 5A:
http://www.dampfakkus.de/akkuvergleich.php?akku1=141&akku2=122&akku3=103&akku4=99&akku5=&akku6=&a=5
Other than some initial sag, the Sanyo ZT held it’s capacity rather well in the 5A test.
For Average current use, I personally use a lot of unprotected Sanyo UR18650ZT cells. These offer a very nice discharge curve and reasonable capacity. The downside is the higher charging voltage (4.30V) is not for everyone (i.e. customized/specialized chargers).
For higher current applications, I use the Panasonic NCR18650PD cells. I’ve only been using them for a while, but so far they perform well in my higher drain (5A+) lights.
I'm a big fan of Sanyo batteries, BUT...
How old are the Sanyo batteries you're buying? Who are you buying them from? Are they old stock? Are they even making them anymore after Panasonic bought them out? Press release I read sometime ago said they were phasing out some of the Sanyo lithium batteries and moving all production to China for all Panasonic batteries.
My suspicion is that the days are numbered for Sanyo 2600mah (UR18650FM). Maybe.
I think Panasonic will be putting more $$ in R&D towards the higher capacity cells like the 3400mah (NCR18650B). The UR18650FM is old news. Sorry old friend. Say good buy to old Yeller. Bring out the shot gun son.
My last ones have date code: 8th week, 2013. Bought in May at FT
Panasonic NCR18650B (Protected if they fit into your flashlight or Unprotected otherwise) is the best overall choice for a stock (unmodified) flashlight that does not draw too many amps from the battery (as most modded flashlights do). Its 3400 mAh capacity means you won’t have to unscrew the tail cap of your flashlight too often to replace a battery nor carry pocketfuls of extra batteries if you find yourself in a situation where you need extended run time.
trume_3454 I think that you may have become a bit confused while doing some searching. This thread is 1.5yr old.
You are right, wight. Somehow, it showed up under my “Recent Posts” or so I thought and I did not check the date. Thanks.
No problem, just picking on you a little. 
the reason? 3400mah