It gets very warm left on for the full battery test on high. Still able to hold, do note that the full run was done indoors with no moving air and a room temp of about 72. After the mods it got much warmer to hot and the test was stopped after about 10 minutes. With the Aluminum so thick during an extended run I can place one ice cube on any one spot of the battery tube and the heat literally melts away from the entire tube. If I bump the current even more I’ll probably add copper plates to the inside of the head to work as a heat mass and wick for even more heat moving.
Thanks Ron,
After removing the wrapper, is the +button top disk securely tack-welded in 2 (or more) places to the cell, or only on one side, to allow the other side to flop around?
I am new to the modern LED flashlights and trying to learn from the contributors here. I hadn’t noticed the Olight X6 Marauder, looked it up… Yikes! $350! I’ll have to search out some reviews. At 1/5 the cost, this J20 flood hammer is looking pretty good. Amazing the J20 can run full blast as long as the batteries can deliver. Thanks for the info.
MB
Thanks for the feedback. Your project to turn this into a mini sunspot is very interesting. I am newb here and trying to learn, and trying to decide what to buy for my initial collection of modern LED flashlights. Its got to include a monster flooder. Looks like the J20 certainly fits that category even in stock form.
I am not too handy with electronics. I have lots of other tinkering interests. So, I’d have to leave hot rodding to others. It seems like this flashlight is a ripe candidate for modding. I can’t help but think there would be interest in a group buy for an enhanced BLF edition.
MB
[/quote] Thanks Ron, After removing the wrapper, is the +button top disk securely tack-welded in 2 (or more) places to the cell, or only on one side, to allow the other side to flop around? [/quote]
Hi
I'm on my phone so inserting pictures is alluding me. Here is a link to the top button. You can see the top button cap is crimped in place. The remains of the spot weld used to run + to the bottom of the battery can also be seen. I hope that answers you're query.
At this price point, the J20 is an absolute steal considering its quality and utility. For those who enjoy modifying their lights, its even more of a bargain.
If you havent seen it yet, check my J20 review.
Thanks Ron. That answers a lot and was very helpful.
The excessive corrosion around the parameter of the top has me a bit concerned. It looks like its been there quite a long time. Great to hear that the seller is replacing it.
I tested my stock TR-J20 with (3) Trustfire 32650’s at 2.96 amps, with a Fluke 36 clamp meter. Now I added a R200 resistor to the empty R12 slot and now it is pulling 7.56 amps. Shocked the hell out of me when I turned it on… WOAH! Ran for 10 minutes on Turbo with no issues. Barely warm. This thing is HUGE and now, It is WAY BRIGHTER!! :D I’m looking at changing out the (5) FET’s (from RMM) testing them and then heat sink them, then try adding another R100 resistor but the Question is how much can you push the stock driver? How much can the XML’s take on these stock stars? If I can push the stock driver to 10-12 amps, I’ll go with XM-L2’s, for now I’m really happy with the way it is……for now…. 8)
My guess is that you’re pushing the driver to its limits now. Those four little MOSFETs are roasting hot at this point. They were for me at 6.33 amps. Encasing in mineral oil or potting in a good thermal conductor is an option. As is the XM-L T6’s on those aluminum stars are probable maxed at 2.0-2.5 amps close to where you are at now. Just going to XM-L2- U4’s is going to bump you up 30%, add copper stars and three amps is probably you max with out plugging it into the wall.
This one has 5 FET’s so I’ll change them out with these…… http://www.mtnelectronics.com/index.php?route=product/product&path=25_76&product_id=213 
I have changed the FET’s out on other drivers, and got quite a bit more current, maybe these cheap ones are not up to the task, we’ll see…. 
The 7”G”10 Crelant driver was 3 amps stock, bridged the resistors, went to 5.8 amps, replaced the FET’s now at 9.6 amps, maybe it will have the same effect?
I ordered some to check them because I have J20s from Trustfire, they are real. I have custom drivers being made for these right now. The Feilong 32650 cells are better than the trust fires. There’s a rumor that they aren’t, but it is a false rumor. The Feilongs put out 5600-5700mah on a 10A draw, tested with a Power Lab 8 battery work station. I will update when the new fet drivers come back. I already had custom buck drivers developed for these. I remove the LED plate and install a copper pill above the driver. Both are shown in the Making of a Monster, thread. In the modding forum here on the first page right now.
My misprint my two TR-J20’s both have 5 MOSFETs. Your driver looks identical to the two I have. Do post after the Mod’s. I’m leaning to do the same.
We spoke about 12 XHP50s and sagging the cells til the cows come home for a “redline” version. But to do this the head needs modification for more cooling. Not ready for that work yet when the first iteration for production with single emitter is still being worked.
This is my pill made for the J20…
WOW!!
Best binned 12 volt XHP-50’s drawing only 1 amp each would put out 18,000-20,000 lumens. Still a very efficient Led at this point, would need to be 4 cell job. Four 32650’s at 12 amps. WOW!!
Well…
We arrived there a much different way, in theory, and it’s a very sensible theory, with respect to saving the LEDs and maybe not ourselves. 6V XHP50s was proposed. I thought about it, 6V MT-G2? Almost at 8V when passing 10.5A through it (I believe 7.8V-7.9V). You’ve got a battle between LEDs, and batteries. In that battle, with 3 cells, the LEDs win. No possible way a cell is going to dump 120A to blow those LEDs, if that would even do it (a lithium polymer pack could!). The moment of ignition, the batts would just DUMP. Don’t really know where they would sag to, but you figure batteries in series, each cell is providing voltage, so that means they all 3 drop the amps they can, like if it were 1 cell and we ignored voltage. 32650, probably 20-25amps? So, yes, maybe over 25,000 lumens at turn on. For how long? Until you throw the J20 and dive into a river, maybe? The J20 switch RMM has worked with, and says it’s a strong switch that could take pretty much all amps you throw its way, it’s beefy, but you gonna click that button? I double dog dare ya. No lighted tailcap mod would be needed, ZAP!
Would definitely need momentary.
The head, being a 2-part, technically 3 part head, the LED plate is not integrated to the main lower mass except via threads which are anodized. My best solution, would be to turn the factory center threads off, using an O-ring seal where the threads were. Then, a big chunk of either aluminum or copper round would be bolted to the rear of the LED plate. That chunk would be male threaded. Where the taper is in the lower head would be bored cylindrical, and receive female threads, so the new bolt on piece becomes the integration point. Now the heat is moving through a large mass, when reaching the threads, the mass is thicker, everywhere, so much better heat transfer into the lower head.
I thought of 12volt Leds to cut the amperage in half. Your Copper heat sink could be mounted from the underside and sandwiched into the two piece head. Considering how thick the base Aluminum plate is, it’ll be very functional even at 150 watts. But with your Copper heat sink underneath it’ll have real run times. It’s definitely a WOW light. 32650’s at 20-25 amps sound a little scary. Four 32650’s at 12 amps or twelve 18650’s at 4 amps sounds better.
Best price I can find now is $65.31, free expedited shipping at GearBest using code: LED2015GB for an 8% discount. Thinking of ordering one. The coupon code in the OP expired.
Look’n for 12K-15K lumens, so I assume U4 1C’s on possibly a FET based zener mod with wiring the LED’s up 4P3S would do the trick. Looking at using the BASEN 26650 4500 mAh cells.
I have 20 XM-L2 U2 0D’s and 20 0A’s coming from Fastech, plus RMM’s 3SFETDDZenrMod driver to try next, I poofed one of the first leds in series, after I added 5 new RMMs FET’s 7.8 amps then added a R050 0ver the R150. It lit once and the second time poofed. I think its at its max and the driver has some spiking. So I reflowed a spare xml and removed the R050 and that where she stands now. Pretty freaking bright!
I was worried about “POOF” the whole time I was just adding resistors. It’s a lot of current through unknown parts. I’ll let you brave through then copy your work. But I’m also looking at using parallel XHP-35’s at about 1 amp each. It’ll need 4 cells. I really like the head’s lay out so a battery pack and power cord might be my option. My goal is 18,000-20,000 lumens with lots of Copper mass under the Aluminum shelf.
It’s 65 flat at windyfire.com, however there is some shipping fee depending where you are located at. Communication is good and active, I am waiting for some batteries from them rigt now.
Dirty spiking current, buck drivers SUCK!