Convoy S11 Active Cooling Project

I have several Convoy S11 flashlights in various configurations. All are fine but only function on high for a few minutes before stepping down. I also have a Lumintop Mach 4659 flashlight which I got specifically for the active cooling fan. I was quite disappointed with the runtime performance. With a battery that size and active cooling I'da thought there would be much better runtime. Maybe I was expecting too much performance benefit when running on turbo.

So I thought I would further my flashlight modding hobby and try to build one myself. I started with my Convoy S11's and chose a cooling fan built for RC Car electric Motors. Then I used thermal tape to keep it on the light and properly transfer heat to the sink. The sink was slightly wider than the flashlight. So I bent it in slightly until it fit snugly on the flashlight.

Next was power. I ended up using 3 different types of LIPO batts all for what I assume is some kind of drone appliation.

• At first I used a ready made power bank which was huge, impractical and way overpowered for just my heat sink fan. It proved functional but adding USB connectors and associated wiring made the whole thing impractical.
• 501646 3.7V Lipo Battery 350mAh - these were maybe 3mm longer than the heat sink and proved to be much more mAh than were needed. Compared with the runtime of a Vapcell K70 26650 these tiny batteries had plenty left over when completely draining the 26800 and 26650 batteries in the flashlight.
• Liter 3.7V 180mAh 501235 Lipo Battery - these fit perfectly on the sides but the mAh were a bit lower then needed so I put one on either side of the heat sink to double the capacity.
• 502035 300mAh 2.0Jst 3.7V Li Lipo Lithium Polymer Ion Battery Pack - these were slightly taller than the fan and heat sink and seemed perfect mAh for what I needed.

With Power I needed a toggle button to turn the fan off and on. So I used a Self-Lock Micro Push Button Switch Flat 2 PIN with Hole Mini ON/Off Push Button. This had wide attachment points with holes in them which made it easy enough for me to solder wires to. To hide my poor soldering skills and for general safety I added shrink tubing to cover the solder and attachment points.

Once I had all the functional parts I needed to hold it all together. When adding magnets to my flashlights I ended up using a heavy duty double sided tape. Effectively functioning as glue.

Once I relearned how to solder, this time properly. then I was able to properly solder all the wires to the proper places.

It was obvious at this point I needed some kind of enclosure. In V1 I used 3" shrink tubing wrapped around the whole thing then I cut a hole in the top for the fan. This was kind of clean looking but very stiff. I thought it might start to tear over time with repeated heating and cooling with normal usage. In V2 I tried self fusing silicone tape. Which was soft and looked a bit cleaner. This added a bit of grippiness as well. It still looked a bit sloppy with the exposed connectors for the batteries.

Initially I tried passive cooling while just slapping some heat sink fins onto the flashlight head, as seen in version 1. It did not provide enough heat dissipation. After attaching the active cooling contraption, version 1 looked like this:

The power button was hidden under the shrink tape just in front of the magnets on the now dysfunctional clip. I ended up slicing a flap into the shrink tape to access the JST connectors for charging the batts.

Version 2 ended up looking a bit better and a lot less cluttered with the silicone table holding everything together. I added black electrical tape to hide the JST connectors and allow for removal so the batts could be charged.

Charging both versions was very cumbersome requiring the heat sink LIPOs to be disconnected from the fan and connected to an external charger.

At this point I realized I needed a charging board for the heat sink LIPOs. With my newly developed soldering skills I ordered a few to practice with.

Version 3 is incomplete due to a tragic shrink wrap trimming accident. I had all but the charging board attached and all most of the wiring concealed in the heat sink fins. then I realized I had no ventilation for the heat sink fins. As I gingerly used a carving scalpel to expose the battery side of the heat sink I punctured the LIPO and small amount of smoke and chemicals began to leak out. So I quickly removed the shrink tubing. the battery had become slightly warm and fortunately no thermal runaway set it afire. I disposed of the battery but now I am left with this:

I am waiting for replacement batteries. Once I have that I will solder in the charging board and double-sided tape it to the LIPO opposite the JST connector and power button. 

Just so I can play with it and do some runtime tests I will wrap it in self-fusing silicone to give it some rudimentary safety and slightly less cluttered look.

What's Left?

• Attach new battery
• Solder wires to the charging board
• Attach charging board
• Temporarily wrap in self-fusing silicone tape.
• Design a proper 3d printable enclosure
• https://www.tinkercad.com/things/j4OXwKQWXhx-flashlight-heat-sink-case
• Get the enclosure printed
• Reassemble with enclosure
• Execute runtime tests.