Single CR123 Modification
I had a chance to get a few of these flashlights for a really great price, so I grabbed them thinking they would be fun to modify. These Chinese made 1 CR123 flashlights have been sold under various names by different vendors, but these units came with no markings. Shown next to a 2AA MiniMag for size comparison.
While there is nothing really special about them, they did come complete with DC/DC converter, 1 watt Luxeon LED, 19mm reflector, and clickie tailcap switch. Out of the box, most of these lights suffered from an obvious phosphor defect in the Luxeon that made for a puke green colored center spot with a purple ring around it. There were a couple units that had a fairly decent beam without any signs of the phosphor defect.
However, when testing one of these "good" units, it didn't take long to find out there were other problems with these flashlights. After only a few minutes of continuous operation the Luxeon began to color shift it's tint from a nice white toward a dirty green color. A sure signal the Luxeon was getting very hot during operation.
Disassembly of the unit revealed the cause of the Luxeon over heating. While at first look the design gives the impression of a clean and elegant design, such is not the case. The Luxeon emitter is mounted to a custom circuit board which is attached at the top of the internal heatsink assembly.
However, when this Luxeon circuit board is removed, the design flaw stares you directly in the face. For some unknown reason, the designer had a recess machined into the heatsink behind where the Luxeon mounts.
Since the custom circuit board mounts the Luxeon slug flush with the backside of the circuit board, the machined recess actually creates a gap of about 1/32" between the Luxeon slug and heatsink. Although this recess is filled with white heatsink grease, it does little to transfer heat from the Luxeon to heatsink. In fact, having a layer of heatsink compound so thick is almost the same as having no heatsink for the Luxeon at all.
Just to clarify this problem for new readers, the purpose of heatsink compounds (grease or epoxy) is to assist the transfer of heat. However, these compounds by themselves are terrible at conducting heat when compared to metals. Heatsink compound only works when applied in a very thin layer between two surfaces. The heatsink compound does conduct heat better than air, so when used between two surfaces it fills in the small microscopic air pockets between the two surfaces which increases the transfer of heat. So to reiterate, by itself, compared to metals, heatsink compound is not a good conductor of heat and should only be used in layers around 1/1000 inch thick between two surfaces to have any benefits.
So, step one for modifying these flashlights is to remove the Luxeon emitter and circuit board. Then clean all the heatsink compound off the heatsink, especially out of the recess where the Luxeon will be mounted later. A final clean up with alcohol will ensure the surface is good and clean.
Mounting the Luxeon is pretty straight forward using the recess to center the Luxeon on the heatsink. Apply a thin layer of thermal epoxy, (I'm using Artic Silver) and gently push down on the Luxeon case to squeeze out the excess thermal epoxy leaving a very thin layer between Luxeon and heatsink. Do not push on the Luxeon lens, as this can cause bubbles in the lens. Push only on the black case around the lens, not the lens itself. Set this aside so the epoxy can set up.
The DC/DC converter in the original flashlight is pretty wimpy, mustering only about 350mA in output. Since I replaced the Luxeon with a BIN TW0J 3 watt Luxeon, a better converter can be used to get more light out of the 3 watt Luxeon.
For this mod I used the converter the MiniPro uses. Any more power than that and the little CR123 flashlight would become a burn hazard. I just want it to be brighter, but not dissipating so much heat that it could burn someone if left operating for extended periods.
To replace the converter, simply pry off the rear contact board and unsolder the existing converter. Now solder the replacement converter is its place, and run the output leads through the existing holes in the heatsink to the Luxeon leads and solder.
Push the rear contact board back into place in the rear of the heatsink assembly. Note that originally there was a plastic washer between the rear contact board and battery. With this insulating washer in place, the only ground path for the converter is through the two small tabs sticking out from the negative ring on the rear contact board. This looks a little cheap to me and could cause problems later with intermittent ground connections. The simple cure here is to discard this washer, as it will not be used.
To improve the circuit ground path, file the top of the battery tube nice and flat with a fine mill file. When screwed together, this nice flat surface will mate with the rear contact board negative contact ring making for a rock solid ground connection.
A final finishing touch is to replace the 19mm plastic lens with a 19mm mineral glass lens of better optical quality and scratch resistance. Assemble the unit by tightening the battery tube up snug against the rear contact board. Do not over tighten, as pressure is applied to the Luxeon case by the reflector when assembled. Use just enough force to snug things together without crushing the Luxeon.
Install a CR123 lithium battery and you're ready to use the newly modified flashlight.
The resulting improvements to the modified flashlight are readily apparent; much brighter and better, whiter tint to the light produced. Also, the thermal improvements made by actually mounting the Luxeon slug in contact with the heatsink will keep the Luxeon working like new. And the improvement to the DC/DC converter circuit ground path will ensure flicker free operation.
All in all, not a bad little flashlight once modified. However, out of the box, this flashlight leaves a lot to be desired and proves once again that just because someone has the ability to mass produce a flashlight, it certainly doesn't mean they know squat about thermal management or other good engineering practices.
Before 535 Lux
After 1250 Lux
I'll have some of these modified lights posted the modder's B/S/T forum later today if you're interested.
Thanks for looking.
Lambda.
I had a chance to get a few of these flashlights for a really great price, so I grabbed them thinking they would be fun to modify. These Chinese made 1 CR123 flashlights have been sold under various names by different vendors, but these units came with no markings. Shown next to a 2AA MiniMag for size comparison.
While there is nothing really special about them, they did come complete with DC/DC converter, 1 watt Luxeon LED, 19mm reflector, and clickie tailcap switch. Out of the box, most of these lights suffered from an obvious phosphor defect in the Luxeon that made for a puke green colored center spot with a purple ring around it. There were a couple units that had a fairly decent beam without any signs of the phosphor defect.
However, when testing one of these "good" units, it didn't take long to find out there were other problems with these flashlights. After only a few minutes of continuous operation the Luxeon began to color shift it's tint from a nice white toward a dirty green color. A sure signal the Luxeon was getting very hot during operation.
Disassembly of the unit revealed the cause of the Luxeon over heating. While at first look the design gives the impression of a clean and elegant design, such is not the case. The Luxeon emitter is mounted to a custom circuit board which is attached at the top of the internal heatsink assembly.
However, when this Luxeon circuit board is removed, the design flaw stares you directly in the face. For some unknown reason, the designer had a recess machined into the heatsink behind where the Luxeon mounts.
Since the custom circuit board mounts the Luxeon slug flush with the backside of the circuit board, the machined recess actually creates a gap of about 1/32" between the Luxeon slug and heatsink. Although this recess is filled with white heatsink grease, it does little to transfer heat from the Luxeon to heatsink. In fact, having a layer of heatsink compound so thick is almost the same as having no heatsink for the Luxeon at all.
Just to clarify this problem for new readers, the purpose of heatsink compounds (grease or epoxy) is to assist the transfer of heat. However, these compounds by themselves are terrible at conducting heat when compared to metals. Heatsink compound only works when applied in a very thin layer between two surfaces. The heatsink compound does conduct heat better than air, so when used between two surfaces it fills in the small microscopic air pockets between the two surfaces which increases the transfer of heat. So to reiterate, by itself, compared to metals, heatsink compound is not a good conductor of heat and should only be used in layers around 1/1000 inch thick between two surfaces to have any benefits.
So, step one for modifying these flashlights is to remove the Luxeon emitter and circuit board. Then clean all the heatsink compound off the heatsink, especially out of the recess where the Luxeon will be mounted later. A final clean up with alcohol will ensure the surface is good and clean.
Mounting the Luxeon is pretty straight forward using the recess to center the Luxeon on the heatsink. Apply a thin layer of thermal epoxy, (I'm using Artic Silver) and gently push down on the Luxeon case to squeeze out the excess thermal epoxy leaving a very thin layer between Luxeon and heatsink. Do not push on the Luxeon lens, as this can cause bubbles in the lens. Push only on the black case around the lens, not the lens itself. Set this aside so the epoxy can set up.
The DC/DC converter in the original flashlight is pretty wimpy, mustering only about 350mA in output. Since I replaced the Luxeon with a BIN TW0J 3 watt Luxeon, a better converter can be used to get more light out of the 3 watt Luxeon.
For this mod I used the converter the MiniPro uses. Any more power than that and the little CR123 flashlight would become a burn hazard. I just want it to be brighter, but not dissipating so much heat that it could burn someone if left operating for extended periods.
To replace the converter, simply pry off the rear contact board and unsolder the existing converter. Now solder the replacement converter is its place, and run the output leads through the existing holes in the heatsink to the Luxeon leads and solder.
Push the rear contact board back into place in the rear of the heatsink assembly. Note that originally there was a plastic washer between the rear contact board and battery. With this insulating washer in place, the only ground path for the converter is through the two small tabs sticking out from the negative ring on the rear contact board. This looks a little cheap to me and could cause problems later with intermittent ground connections. The simple cure here is to discard this washer, as it will not be used.
To improve the circuit ground path, file the top of the battery tube nice and flat with a fine mill file. When screwed together, this nice flat surface will mate with the rear contact board negative contact ring making for a rock solid ground connection.
A final finishing touch is to replace the 19mm plastic lens with a 19mm mineral glass lens of better optical quality and scratch resistance. Assemble the unit by tightening the battery tube up snug against the rear contact board. Do not over tighten, as pressure is applied to the Luxeon case by the reflector when assembled. Use just enough force to snug things together without crushing the Luxeon.
Install a CR123 lithium battery and you're ready to use the newly modified flashlight.
The resulting improvements to the modified flashlight are readily apparent; much brighter and better, whiter tint to the light produced. Also, the thermal improvements made by actually mounting the Luxeon slug in contact with the heatsink will keep the Luxeon working like new. And the improvement to the DC/DC converter circuit ground path will ensure flicker free operation.
All in all, not a bad little flashlight once modified. However, out of the box, this flashlight leaves a lot to be desired and proves once again that just because someone has the ability to mass produce a flashlight, it certainly doesn't mean they know squat about thermal management or other good engineering practices.
Before 535 Lux
After 1250 Lux
I'll have some of these modified lights posted the modder's B/S/T forum later today if you're interested.
Thanks for looking.
Lambda.
