So the XM-L2 crash testing thread by djozz got me to thinking about how I should go about overdriving the XM-L2.Because there was little doubt that I should indeed overdrive the heck out of it.Say, 5.8 amps worth.I have no problem using single L-ions but have no interest in using multi L-ions in series.Next best bet would be 4 Nimh in series which, when done with a cell configuration capable of providing high amp draw, leads to over heated 7135 chips and overall malfunction.My own experience with this effect was in a 2D Mag running 8 eneloops in 4s2p configuration (https://budgetlightforum.com/t/-/15493#node-18102).
My plan was simple, use the 2D mag host with the V8 reflector from the post above, replace the XM-L t6 with an XM-L2 U2 on noctigon, and slave a 2.8 amp nanjg 105c to a 3 amp nanjg 105c 3 mode for a total of 5.8 amps.
While the higher forward voltage of the XM-L2 vs XM-L would take some of the stress off the 7135 chips, I decided to thoroughly heatsink the drivers using a 3 layer copper sandwich attached to the chips with thermal adhesive.
The smaller copper donuts on the outside are thermally connected to the center donut with copper strips also attached with arctic alumina.The aluminum heatsink is counter sunk to accept the slaved driver and its copper heatsink and the large copper donut is thermally adhered to the bottom of the aluminum heatsink.
This solution has allowed me to run these drivers at about 5.75 amps for as long as the batteries are capable, with no other issues.How bright is it?Observe the beamshot below.The XM-L2 mag is on the left…Fenix TK41 on the right.Makes me giggle a bit.
Trak tuned, I just upgraded the driver and emitter of the build in the referenced post. Essentially, a hunk of aluminum rod from speedymetals for a HS and the V8 drop in from DX with everything but the reflector removed. Works well as the V8 reflector is designed to focus without the a pedestal.
Gtamazing, Yes still 4s2p config in a custom battery carrier.
RaceR86, Yes I used the stock switch with the bulb tower removed. I do wire the battery positive directly to the emitter positive with another wire from the switch positive to the driver positive. This eliminates switch resistance while still providing power for mode selection.
Here’s something you might try. I have a triple XML2 4D mag mod I am running with 8A worth of 7135’s. I used 1” copper discs with kapton tape to remote mount 7135’s. I cut the tape where the ground tab of the 7135’s could sit. Then i heated up the discs and put a little solder on all the bare copper spots for the ground tab then a little flux on the 7135 ground tabs then basically reflow the 7135’s around the discs
This is the only picture I have. The two I ended up using in my mag have 6 and 7x7135s each for 21 total. Arctic aluminum them to shark type heatsinks in the mag tube.
Using 2p4s eneloops i was only getting 6A at the tail. Using 5 x eneloops in series i got the full 8A. I ran it for a few minutes like that before i glued everything down and it really didnt seem to heat up all that much. I tried the same 5x eneloops on a 7135 board with the chips just stacked on top of each other and that thing got scalding hot in under 10 seconds.
it's a neat reflector but if I had to do it again I would go with a LED mag reflector, much easier.
Bob, great idea with the remote 7135 mounting, I have a tripple XM-L T6 mag I run off 3 slaved 105c drivers and 2s4p eneloops in a 2D mag for just over 8 amps. This combo seems to have just the right combo of battery sag and forward voltage to make it work without heatsinking the chips. I wonder if I should re-think my plan to upgrade to XM-L2s. Course there's always that wide body 3D on my work bench...
I make my own heatsinks for wide body mags from filed down 1 1/2 inch aluminum rod from speedymetals.com. One BLF member recently posted a mod where he JB welded some metal rod to a bolt and chucked it up in his drill. He turned down the diameter to fit and cut a nice driver pocket in the back. Gonna try that on my next mag mod.
