This is a function of the driver, not the LED.
The Sky Rays 3*T6 have built-in driver LV cut off at under 3V. Unloaded the battery bounces back up to 3.2-3.4V when i measure immediately. By experience on the discharger that means about 2.5-2.6V loaded. The 20 plus failures reported here involved driver failures which induced a dead short across the terminals. There is a very heavy electronic components burnt smell. With protected cells, you are safe, the cells just shut down when that happens and recover when the short is removed. With unprotected cells, most of them anyway, you will get a Li-ion fire. Some cells like IMR or Panasonic NCR18650A and NCR18650CH I guess you will get away with it.
Other non triple XM-L lights like Fandyfire STL-V6 also have LV protection. You cannot 100% rely on the cells because on very low current draws, usually the PCB protection won't trip.
Charging also needs protection but seriously sometimes the protection also does not work, the cheapest of the cheapest chargers and even some which are somewhat more expensive in the 15-20 bucks range do not stop charging at 4.2V exactly. I know my Trustfire and Ultrafire WF-188 chargers could pump to over 4.23V when i leave it for a few hours more after green with some low internal resistance cells. I think trooplewis tried over 1 day in the garage as he totally forgot about it and it was close to 4.3V, that is very very close to a Li Co fire. That said, my IMAX B6 is pretty steady, it stops at 4.17V. Seriously there is very little capacity to be had from 4.15V to 4.2V range, probably less than 50mAh for that 0.05V, so in real life you actually won't notice. (look in detail the discharge curve, there is a VERY big difference in capacity for 4.2V discharge to 4.1V as compared to 3.9V discharge to 3.8V)
While the voltage protection of the PCB quite often does not work esp when you need it (ie you totally forgot about it because you are charging "outside" hence no visual reminder), the dead short protection works 100% for all my batteries, including the Trustfire flames.
Check out what i have written above - people have the thinking that 1 cell lights are safe. They avoid multi-cell lights. In reality, there is some added safetly for 1 cell lights but it's probably not a big difference, not in the budget realm that we are dealing. Tailstanding a P60 XM-L and forgetting about it on high is a recipe for disaster, just a game of chance. Seriously, having a false sense of security and sticking to 1 cell lights is worse. Safe Li-ion procedures/handling and frequent DMM voltage measurements is always the best.
No problem man! Hope the info helped. :)
PS, I have to clarify, there are 12 x 18650 lights, and for those....i think no matter how careful you are, it is still way too dangerous as compared to a 1 x 18650 light with protected cell. hehe... There were explosions (pipe bomb, cells inside light) even with IMRs. They were custom incan lights.
The RC fraternity always deal with multiples gunning at a much higher level than flashlights. But 99% of them are very picky/technical about cells usage and charging (their packs and mobile charging equipment probably costs more than some of our budget collections here LOL!), and even when they do vent during usage it's alright.
I have the same question, what can be safer?
the geniune TR-3T6 when the battery voltage under load drops to low the light goes into low mode only letting you know its time for a battery recharge i consider this as a low voltage protection, the geniune TR-1200 does the same thing.
I just received my UF-H3 headlamp and UN-protected batteries. I ordered the protected ones but I got un-protected instead. The worst part is that one of them was DOA....
Has anyone had any luck with getting DD to fix this mixup?
DD will usually fix it - but it will take a few days of msg'ing back and forth with them through their customer support system(avoid email and live chat), and possibly a paypal dispute/claim.
Open a claim through DD CS. It took 2 day for them to reply. I also contacted Summer (BLF member) he sped the process. DD gave me a $10 gift card shortly after speaking with Summer. He/she took care of the problem. Kudos to Summer!
I got a full refund, no questions asked, and the dispute was closed, but not from my hand. I thought that I was the only one to close my dispute.
The money was already send back to my bank account so I guess that PayPal themselves have closed the dispute which is all right.
Now I could re-order but I don't dare, I also think that the 20% off is'nt valid anymore.
I have received a $15, $20, $30 and $50 giftcard from them through DD's CS before. (Yes they mess up quite a few of my orders) I think they just don't understand too well most of them time.
I decided to give dd one chance to make it right. "otta" promised in online chat the items I have originally ordered to be immediately sent. If the cells are unprotected or they do not arrive before the date that's my last change to open a PayPal case a dispute will we opened that's for sure. And after receiving the correct items I'll just close the PP case.
I ordered 6 pairs of PROTECTED ones, and I have included this paypal note: 
"Please, be sure to send me PROTECTED batteries as the item's title says".
I really hope they send protected!, I have an upcoming project and I can't use unprotected batteries at all.
The first batch I've received from DD were ok; original, protected flame Trustfire. Yesterday, surprise! Unprotected, and probably fake (looks the same as fake eBay cells we were mad some time ago).
Unprotected on the left, good one on the right.
When did you order the protected flames and when did it shipped?
When did you order the protected flames and when did it ship?
I've ordered protected cells on 10/09/2011, and second batch was ordered on 10/20/2011, arrived yesterday.
Thanks Hrvoje.
my order finally came... with un protected cells. time to contact CS
I don't expect any order shipped before 8 November to be protected.