Pretty straight forward mod that I wouldn't bother documenting if this light didn't have several thermal bottlenecks. I did a review of this light here.
Overview:
- XP-G2 T4 3C
- FET based DD driver with Star Off-Time Memory FW by BLF Member, JonnyC
- Normal resistance mods (copper braid springs, etc)
- Thicker rubber o-ring under the lens to allow full focus to be achieved.
Went with XP-G2 for 2 reasons. First, the light has thermal challenges that would require much more modding to use a high current xml. Second, the lens in this light creates a big hot spot. An XP-G will still produce a decent sized hot spot, but it will be more intense for better throw. Left on dome as I didn't want to lose any more lumens.
Mod Details:
I'm only going to cover the thermal mods as the emitter, driver, and resistance mods are just SOP changes.
First resistance point is common to most lights. Aluminum emitter base. Using standard fix of direct-path copper base. I'm only covering it here because I'm reflowing the base to the pill so that I can used the light without the reflector.
Didn't put much energy into lapping due to reflow. Just made sure surfaces were flat and not oxidized. Did take down to copper. Mouse over shows the type of solder used. It is silver bearing and is used by some for HVAC work. Its flux is not compatible with electronics. So it's important to clean up well after a reflow. I used this solder because it conducts heat better and because it has a higher melting point than normal solder.
First filled that little pocket on the back with solder and then placed on the pill to reflow.
I like the solder to come all the way up the sides of the base. Base has to be pushed down to have as thin a layer of solder under it as possible. The emitter and leads will use normal electrical solder.
Played with focus a little. Focus was best with no spacer. Just used kapton tape for those inner contact pads on the SinkPAD.
Here is the second thermal bottleneck. There is a thin wall around and below the pill. The head starts to taper to a thicker wall about .2" (5mm) below where the pill bottoms out. Heat has to travel down a few thread windings and then a thin .08" wall before reaching the portion of the head that thickens. The thread valleys are thinner than .08" (2mm).
1" copper coupling cut to make thermal bridge. It has a taper to make better contact with the portion of the head that widens. Here is the bridge in the head with the pill in place. Mouse over shows view from the top after I added another copper layer and then reflowed it to the head. Solder doesn't adhere to aluminum, but it does fill some of the micro gaps and tins the copper to protect against oxidation. Also helps inhibit a galvanic reaction between the copper and aluminum.
1" copper coupling was just a touch to wide. Used a drill and wet sand to bring the diameter down just a little bit. Mouse over show the taper starting to be made. That is a screw driver being used to hold the copper coupling.
Cut off length needed using a pipe cutter. Mouse over shows pill contact surface portion being lapped for better contact.
Here is how the bridge will contact the pill.
An easier solution would be to tightly pack aluminum foil in that dead space under the pill (but above the driver retaining ring). Might work fine as there is a lot of space in there for the foil to make contact.
The third thermal bottleneck that that there is really no thermal connection to the sliding part of the head that has cooling fins. Just a rubber o-ring. Used a piece of copper wire to make an o-ring that will conduct heat. Used a hammer to tap the wire into a flatter shape and to reduce its diameter. Mouse over shows the completed copper o-ring.
Smoothed the bore a little with 2000 grit wet sandpaper. Chucked the head into a hand drill using PVC plumbing coupling, a rubber band, and some electrical tape to get a tight fit.
Used a thin layer thermal paste to act as a lubricant when I assembled the light. If I really wanted to improve the thermal connection here, I would bore out the sliding portion of the head and insert a copper sleeve. That would help wick the heat faster from the copper o-ring and transport it up and down the head faster.
Finally, the tail cap switch has an aluminum retaining ring and a brass contact plate. Here is what the aluminum ring that is hidden by the brass contact plate looks like.
Results:
The above mods really helped. Even just running at 3.3 amps, the light gest hot fairly fast. Replacing the rubber o-ring with copper wire degraded the sliding action. It's acceptable trade off for me. I may try to improve that part of the mod. I got a couple ideas I would like to try out.
I must have done something wrong with the driver or something. With a King Kong ICR cell charged to 4.17, I'm only getting about 3.3 amps to the emitter. Tried a high current Samsung cell and only got 3.75 amps. Also, I lost all the modes and only had high shortly after I started using the light. I'm pretty sure the FET's output tab is shorting against the pill. I meant to put kapton on it before final assembly, but forgot. I'm will have to figure out what when wrong later.
Throw improved from 24kcd stock to 78kcd at 3.3 amps. Without the reflector, throw dropped over 10% to 70kcd.
The reflector has a subtle influence. Here is a wall shot without the lens, but with the reflector. Without the reflector, its just a uniform light with no apparent hot spot. Wall is beige colored.
BLF Member, unknown00101, gave me some good advice here. In my rush to rap up the light, I didn't do what he said, but will next time I open up the light. I did extrapolate his idea to the flat outside portion of the reflector. I blacked it out with a permanent marker. Doesn't really full absorb the light, but it does mute the outside beam artifact considerably. Thank you unknown00101.
Beamshots:
It's raining and very humid. So not good conditions for trying the light out. Here are some shots with mouse overs to the stock beam.
Tree is about 250 feet away and 70 feet tall (High mode).
About 225 feet and 20 to 30 feet high.
Conclusion:
These mods improved the light considerably. It's a nice general purpose light with a cool form factor. I'm a fan of the light and it's my best small-sized zoomie. I would like to get the emitter current up to around 5 amps with a short turbo step down.
I wonder what the throw would improve to with a higher binned xpg2 dedomed and driven at a higher current. I hope someone out there finds out because I want to keep mine more in the tame realm for now.
