Hello
Which 18650 battery do you use or recommend?
Till now I was using NCR 18650B 3,7V 3400mAh (green color - panasonic).
Is this a good choice or do you recommend some other batteries?
Thank you
Kind regards
This is more complicated than it seems. There are two parts in a protected battery. The battery itself, which you want to make sure it made by a reputable manufacturer. The NCR18650B clearly meets that criteria. The second part is the protection PCB. The rub is the protection PCB is ‘aftermarket’. That means it was provided by and integrated into the battery assembly by one or more third parties. Panasonic, Sony, Samsung etc. do not make protected batteries.
The only real question is whether or not the NCR18650B is the best battery for you intended use. It is not a high current battery, so if the intended use is going to draw more than about 3.5 amps, you might want to look at battery with higher current capability such as NCR18650BD, and if you need really high current such used in portable power tools, then you want a true IMR battery such as a Samsung or Sony. These very high current batteries in generally are not available with protection. The upper limit on protection PCB’s typically about 7 amps. However the IMR battery chemistry is much more tolerant of abuse than ICR batteries, so protection is generally not needed.
So the real issue becomes are you buying a protected battery from a reputable source who really did use a quality cell like a Panasonic and did they use a quality PCB and packaging to add the protection to the cell. That’s a much more difficult question to answer.
Thank you for your detailed answer.
I need batteries for BLF Manker A6 (link below) and also later for some other group buys.
Is NCR 18650B good choice or what should I choose too get max lumens?
Thank you
No, it isn't. I would go for the Samsung 30Q or LG HE4. The first one has a higher capacity.
Panasonic NCRxxxx with PCB… only for an enemy!!!
No. In this case I prefer NCR18650BD.
Yeah you are asking for cake and the eating of said cake. If you want the highest lumen output you’ll need to go with good quality unprotected hi drain cells. If you want the best protected cells that will still give good output I’d check out mountain electronics. Richard carries high quality protected and unprotected and knows the cells he sells and will give you good advice and a good price so don’t think twice. Take my advice. Shrimp fried rice. Ok I went a little too far there. Sorry. The rest is serious though. :bigsmile:
If you've got a good charger, you don't need a protected cell in this light. It got under voltage protection which kicks in at 2.8V.
Can you please give me the link to online shop.
Thank you.
Where can I find them, can you please send me a link?
Thank you
Sorry :~ , who is Richard?
I’m afraid to use unprotected cells. If I buy unprotected cell, what do I have to watch for?
I have this baby 
Xtar VP2 2
http://www.gearbest.com/chargers-batteries/pp_94496.html
Do I need protected cells?
Please excuse me for so many replies.
Thank you.
Things are changing with flashaholics :)
At the days I was starting people were considering protected cell as a holy grail, and must for safe use.
No one recommended me unprotected cell saying: "Stay away from unprotected cells", "you will overcharge", "you will over-discharge", "keep your eyes and ears wide open if you use unprotected one", "you will be worried all the time and you'll not have piece of mind.
I recommend LG18650D1 protected. It will be suffiecient for all factory lights and moderate modded ones.You can't go wrong with protected cell(or you can cause it may not fit to each light or charger). If protection dies you can always unwrap it and have unprotected one.
Gregor - If you have good charger with "overcharge protection" (you do) and good light with "low voltage protection" (A6 does) - then you can use anything.
Look at Dale's chart in the OP of the A6. Even the cheap Sanyo laptop salvage and Samsung 26F (both not the high drain) do very well :)
Protected on unprotected - this is now the question. 
Now I really do not know what to choose.
Can you tell me your top choice for both variants.
Thank you
Is this the chart you are talking about:
For max lumens, which cell will you choose?
What means: “No spring bypasses”
Thank you
Gregor, whathever you choose out of good brand cells you won't see big (if any) difference with naked eyes since human eyes are adaptive. If it would pull more current it would heat up more, have bigger voltage drop and give less light in a short time. So it's not worth to hunt for highest lumens output just by choosing batteries and you even can't notice the difference.
Hvala neighbour.
What will you choose?
Thanks
Js mam 20 novih Xtar 18650 2600mah z zascito, 5€/kom
Hello koyotee 
I’m looking for higher capacity… cell.
Kind regards