As long as you don’t run the batteries right down and they are balanced (holds charge similarily after 24 hours) check them before putting them on the charger, if one is draining substantially more it may have a lower internal resistance.
As long as you are already monitoring them and are used to it there is nothing wrong with it. I actually prefer the unprotected cells and have no issue a tall with them as long as they are run singly or in parallel. For series lights I'd rather run protected just to be safe. ;)
Are these still the best bang for the buck? http://www.fasttech.com/products/1420/10001901/1143802-sanyo-ur18650f-18650-2600mah-protected-rechargeabl
I like their discharge curve compared to high mah batteries. I would really like to get these but I cannot afford to buy 20 of them. http://www.intl-outdoor.com/2-pcs-panasonic-ncr18650pd-2900mah-protected-battery-p-671.html
I mostly use unprotected LG and Panasonic cells harvested from laptop battery packs. No problems, so far - yet, I do not run them down (not anymore, that is -I’ve learned my lesson).
JohnnyMac has already said everything which would be important.
The unprotected Pana PD 2900’s are at FT for a reasonable price. I just landed six of them and they all have a tested capacity of 2600mAh at 1A discharge to 3.0V.
I put them in my BTU (4.5A) and in a 2x18650 ZY-T08 MT-G2 mod (5.8A). They seem to do the job.
As far as protected go, I mostly use unprotected and have little experience with protected cells. I only have them for gifting/loaning and in some lights that don’t have low battery warnings.
I use unprotected cells most of the time and they work great. some lights have connection problems because the unprotected cells are usually shorter though.
Maybe I'm overly cautious but I'd never run unprotected Li-Ion cells in series - period.
And I know this is BLF and not CPF but I'm having a hard time understanding why anyone would shell out the necessary for high quality, high output lights like the TN30 or BTU Shocker and then feed them with ****fires or laptop pulls.
Could be just me.........
Do you really need to buy all 20 right away?
I was wondering the same thing myself to be honest…
I don’t use unprotected cells myself, but I can see two reasons why people would want them.
- Higher currents
- Cheaper
For better cells, they do have higher currents because there is no protection circuit to trip. The Panasonic NCR18650PD protection circuit trips at 7A, which is still very high, but nowhere near the amps it can reach without a protection pcb. Unprotected, it can reach 15A. Not to mention protected NCR18650PDs are around $30 a pair, while unprotected are just $14 a pair.
Laptop pulls are not dangerous as long as one takes precaution and shows respect. Sure, they’re not fool-resistant like properly protected li-ions, but they are a good source for quality power. (I’m not saying that protected li-ions are fool proof though. :D)
I like it 
I initially wrote fool proof but realized that it wasn’t very accurate. 
- A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.
- Douglas Adams in Mostly Harmless (1992)
I have TrustFire 3000mah batteries because based on most of the tests I've seen they perform similar to a Sanyo 2600mah battery.
I believe most of mine do but some are inconsistent. I also don't think they can handle 3+amp flashlights very well.
I really would like to order 20 of them because I like to have batteries in the lights I use frequently. I would realistically need about 30 including my EDC, P60s, and C8 sized lights. However, most of those lights wouldn't benefit from a 10a battery.
How much are you buying these for?
Because the Panasonic NCR18650As are 3100mAh at $14 a pair, probably cheaper if you buy 10 pairs.
$12.71 per pair for 5 or more pairs at Fasttech
Oh, the price has come down then. Maybe I’ll buy a few more…
EDIT: you linked the unprotected batteries. For protected batteries it’s $1 more: http://www.fasttech.com/products/1420/10001980/1141103
The only thing I am afraid of with all of the Fasttech protected batteries is the additional clear casing making them too large in diameter.
Or is that common amongst all brands and I am just noticing it because the casing is clear?
Very true, cuz that's what the OP seemed to be looking for. 
>>>>>high output lights like the TN30 or BTU Shocker and then feed them with **fires or laptop pulls.
New is new whether you get them from fasttech or pull them from a NEW power pack.
And they’re essentially half what Fasttech charges.
I’m not saying FT’s 2900s are fake, but who really knows about other vendors. With all the fake battery labels floating around, really the only way you can be 1000% sure of whether a battery is real — Get it from a name-brand battery pack! No way a company like Acer will use anything but real Panasonic batteries.
But I wholeheartedly agree about the TF flames. Why buy something iffy when you can buy a name-brand quality battery for a few bucks more?
Of course, the protection circuits in any of these batteries are made by who-knows in a tin shack somewhere in China. Considering the quality-control level of all things Chinese, I sure wouldn’t bet those circuits will work as designed in an emergency situation. But since they are the only thing available, I use them in multi-cell situations in both series and parallel setups. I have ’em, so I might as well use them. Have I used unprotected cells in parallel lights? Sure. But not on a regular basis. I ALWAYS use protecteds in series lights, but since I only have a couple series lights, I don’t do it much.
I am one of the few who actually had a 14500 ultrafire KAPOW while charging, so I don’t use ANY Chinese *fire batteries. Don’t need to. Have like 300 batteries (almost all pack pulls)! Which reminds me, I think it’s getting to be time for another battery giveaway!!!