I need to purchase a few more rechargeable 18650 batteries and would like some good ones.  I'm currently using some Ultrafire 18650 batteries and they've lasted me a long time but I've read a bunch of bad reviews about them.  I'll be using them on a Fenix TK15 and PD31 lights.  Are there better options out there?

The AW brand (sold exclusively on CPFMP) is considered very good, but the Panasonic 18650s made in Japan are less expensive and have tested well.  Make sure you get protected ones...  I just bought two additional 3400mah protected Panasonics on eBay for $22 delivered (I already have two and am very happy), whereas the AW 3100 cells are about $25 each.

Also, there's this link.  Let me apologize in advance for going full nerd on the first reply.

http://lygte-info.dk/review/batteries2012/Common18650comparator.php

Thanks. Your response makes sense. I was actually reading about those two but wasn't sure about them. I'll definitely look into them more.

There are many different brands of 18650s but the actual cells are made by only a few manufacturers. Sanyo, LG, Samsung and even Sony make good cells but Panasonics are still the most popular and widely available. I believe that the standard 4.2v cells are still only hitting ~3100mah capacity, most of the newest 3400mah cells need a specific charger to hit their full rated 4.35 voltage. Fenix makes great lights and I'm sure they probably both have low voltage warnings or cutoffs but I would still recommend spending a little bit more money on protected batteries in case your charger is not entirely trustworthy or should you buy different flashlights in the future.

In terms of reliable brands there are plenty of options, Fenix of course, FourSevens, Efest, Orbtronic, Keeppower, Eagletac, Redilast, Callie's Kustoms, Xtar, etc. You could also order from someplace like Dealextreme, FastTech, Intl Outdoor, Mtn Electronics and such, like the above mentioned brands they all add protection circuits to the bare cells buy they don't rewrap them and try to sell them as their own brand.

There are some fantastic reviews with lots of test data available here: http://lygte-info.dk/review/batteries2012/Common18650comparator.php


Edit - Just noticed Dallas' reply, AW's are indeed fantastic as well - I actually have 5 of his.

Panasonic NCR18650B 3400mah

Three recommendations for the Panasonic batteries already. I'll definitely start there. Thanks guys.

I like the AW brand of rechargeable lithium-ions. Lighthound sells them.

Had plenty of AW 18650s over the last few years and they're great. Noticeably last longer for more charges and tend to hold together longer then any other 18650 I've tried. I always buy from lighthound too.

Orbtronic 3600 mah

You can also find the Panasonic batteries in the ones branded by EagleTac and Olight.  I run the EagleTacs and they are GTG.

THIS!

One caveat, only purchase from a TRUSTED vendor.

LOTS of counterfeits out there

One side note, the Panasonic 3400 maH I have will not fit inside my Zebralight SC600. The AW's will. The diameter is SLIGHTLY smaller.

The Ultrafires vary depending on color.  I too have had great luck but specifically the Marroon 2400s.
Last I looked they were available someplace at 6 bucks. Trustfire flames are good for the money paid but you have to be sure you are getting real ones and not fakes.

I've had great luck with Spiderfire 16340s but the same name in 18650 is reviewed as pretty much complete crap compared to competitors.

Lots of good advice here.  I have 8 AW's & 6 of the Panasonics and both are really very good.  You will not go wrong with those.  I have two SC600 zebras and agree the AW fits perfect while the Pana is a little to fat.  Lighthound is great to deal with and usually have very good prices.

Right....this plus Orbtronic and AW.

Thanks for the response guys.

Ahhhhh a real light. The SC600 is hands down my favorite light. I'm use then shit out of it at work, it sees hours of continuous use and never skips a beat. On my third one only because I loose them.

I bought a 16 pack of ultrafire red/whites, all were complete duds, total waste

Check out this light...LINK

Wow that's incredible. Won't be long before Zebralight come out with a even higher lumen light lol.

This in no way contradicts what I said.
http://www.ebay.com/usr/hkequipment?_trksid=p2047675.l2559
Has been reliable for me.  I've 3 14500 flame cells.  Haven't gotten any 18650s lately.

Also the Spiderfires were the bright yellow 1000mah ones.

Except that the thread was for the best, not cheapest acceptable.

Indeed. Thanks.