So each emmiter is getting 15 volt ?
Umm no, in parallel each emitter would get 15 volts, in series each get 15/5 = 3 volts. Series is a voltage divider circuit, parallel is a current divider circuit.
Im with you now. Hard night on the turps
Yeah... I would expect your particular J12 to run really hot. Those 55 Watts have to go somewhere. So your comments confirm my suspicions. Yeah my cells also get REALLY hot too, but only towards the end of the run, as battery voltage drops and the driver pulls near 6.5A. My cells remain cool from 4.2~3.35V, its only that last ~20% battery capacity when they really heat up.
I wonder if they messed up and installed a different driver in yours?... or mine? Just to double check, I just ran mine on 2x26650 cells, ceiling bounce tail-standing in a 70F room for a 5 minute timed run and my light was very warm around the heatsink area... but not "painful to the touch hot" or uncomfortable to hold at the heatink. Of course the battery tube was only slightly warm at the +B end.
Whats got me puzzled is your wattage almost doubles with 2 cells, compared to 3 cells... so strange. Yours is a different beast entirely.
Yes strange. But you above post backs up my thoughts its regulated at 7.5 amps its not the out put, another gent sort of backed it up on your thread also. When i say it will hurt your skin this goes for if you shine the light on your skin for a few seconds or hold it by the head for a bit.
Just wanted to post update on the TR-J12 spring issue:
The spring, as it turns out, *does* have inferior plating. As well, there was a good coating of oxide on all surfaces of the button. I used a dremel with a flat aluminum oxide stone to grind the plating off of the top of the spring, as well as the inside of the button. I no longer have the heating issues, but the spring no longer has it's original tension, so I'm going to remove one from an old Q5 driver for replacement , as it seems to be of identical dimensions to the TR-J12 spring.
Before troubleshooting this issue, I had written to T-mart, describing my issue. After the requisite response of "Check that the batteries are charged, etc.", they promptly issued me an RMA, which I will not use. I like T-mart, because they have a Brooklyn warehouse, and I don't have to wait forever to get the items from China. And, apparently, they seem to have good customer service.
Where did you buy yours from ?
x2... My +B spring seems to have lost some of its original push-strength. Even though I gently re-stretched it, and stuffed it with copper braid.
benckie, I'm assuming you directed that question at me. I got mine from the e-bay storefront of Tmart, "campingsurvivals". Because of the US shipping, you have to pay a premium, but sometimes I just hate waiting for China Air Post. And in this case, I only paid about $10 more than if I would have bought it from most Chinese retailers. Their regular website is tmart.com.
Running at that high of heat you basically annealed the spring, you changed it’s material structure and made it softer.
Yes just wondering as my spring is holding in there no problem sofar but my light was brought from manafont.
Unless there is a failure, each emitter should never have 15 volts dropped across it.
The Vf of the XML LED is in the 3.X range. This will not change depending on connection configuration. With 5 connected in parallel, the the output of the driver will be 3.X volts with all the LEDs sharing the current, so their current draw is additive.
However, when connected in series, the total voltage from the driver is the sum of the Vf from each LED and the current is exactly the same through each LED. This method of configuration is better, as LEDs are current operated and the output from the LEDs should be more evenly distributed.
Also, rating the LED regulation rating at 7.5A is fair if this is the standard method used for all of their lights. Ultimately, all we care about is the sum of the current draw of each LED. It is a little misleading, as it implies that the LEDs are connected in parallel, but in terms of determining how hard the light is driven, it does not matter whether connected parallel or series.
I believe the 7.5 amp is regulation not out put like first thought, Ive had my new DMM here for a while just been to busy to test, Ive also found my fluke so when i have time ill have to charge up and few set’s of batteries are test will all the meters to confirm my current draw.
How this light this compare with the Sky Ray King in terms of brightness, throw, etc.
Thanks!
will let u know when i recieve both of them 
mine is doing the same thing? Should I be worried? Also off the topic, but any battery recommendations? Any differences in say, comes with flaps, raised tab, flat etc?
This screams: inssstalll thhe bbeaaasttt drriiivveerrr !!! 
Not to thread hijack but my springs on top & bottom are broke any guides to fix them or retail where I can fix the tail cap?
Can I get an update to this thread? How are your TR-J12’s working now after a couple of years? Are they still as bright? Did anyone contact Trustfire with the spring issue to have them improve their quality control Did you move on to a better/brighter flashlight? Thanks.