Arc-Finity Screw-In Adapter Kit

User Modification: ArcFinity Screw-In Adapter Kit, $(No longer available).
Manufactured by "Ted Bear" on Candlepower Forums (
Last updated 12-10-09

Do you have a CMG Infinity flashlight you're just not happy with because it's too dim? Got an Arc AAA flashlight that you wish would run longer? This easy-to-use and very inexpensive kit allows you to merge the two: you get the Arc's brighness with a long runtime like the Infinity. Though not quite 40 hours, more like 24 hours or so, versus 4 to 6 hours you get with the Arc.

The ArcFinity mod comes with a screw-in fitting that holds the Arc illuminator head and screws into the Infinity, an O-ring, and a metal washer you drop in the Infinity's battery compartment.

Since I'm not an instructional manual writer, I'll try to keep this simple:
  1. Get an Infinity and an Arc-AAA and disembowel them. You'll need to use the Infinity's battery compartment and the Arc's head.
  2. Open up your kit and dump all the parts out in front of you. You should have a large metal collar-like thing, a rubber O-ring, and a small metal washer.
  3. Drop the metal washer into the Infinity's battery compartment, and drop in a fresh AA cell, tail-first.
  4. Push the rubber O-ring up and over the smaller O-ring already on the Arc's head. The new (larger) O-ring should rest directly in front of the smaller O-ring already on the Arc. Things are a bit tight, so take your time and work the new O-ring up and over the old one. It will fit, don't worry.
  5. Start screwing the Arc's head into the threaded opening in the adapter ring. It will become tight almost right away; this is where your pliers come in handy. Use the pliers to turn the Arc head. The action should be tight, but smooth. If it locks up completely right away, this means you've probably crossthreaded the two. Back it out and re-thread it. Continue screwing the Arc's head into the adapter until your pliers can no longer grip it; this should leave the head anywhere from 1/16th to 1/32th of an inch from being flush with the face of the adapter.
  6. Finally, screw the new adapter + head assembly into your Infinity's battery tube. It should light up by the time it's a turn or two from hitting bottom.
  7. Enjoy.

Here are a few pictures to help describe what's happening here.

Installing the washer in the tube and the new O-ring onto the head.

Threading the Arc head to the adapter and screwing it with pliers.

Fitting the finished kit into the Infinity body.

Change the battery just like you do with the Infinity or the Arc-AAA: unscrew the head, dump out the old battery (watch out for that washer, and drop it back in the tube if it falls out) and put in a new battery, tail-first, into the battery tube. Then screw the head back on.

Battery life for this mod should be in the 18-28 hour range; and will be tested to give an exact number.

Like all of the modifications and kits originating from Candlepower Forums users so far, this is yet another professionally-made piece. The adapter insert started its life as an empty CMG Infinity head - just the metal part with no "guts". They are then tapped & threaded inside to fit the Arc's head. A small metal washer is needed in the bottom of the battery compartment to take up the extra, ensuring the battery's (+) nipple will reach high enough to contact the button on the base of the illuminator and turn the light on. An additional O-ring is provided for you to install on the Arc's head to increase water resistance of the finished flashlight.

So why would you want to waste two perfectly good flashlights to make one mutant flashlight? There are a couple of very good reasons. First and foremost, a lot of people have wanted a single-AA LED light that was brighter than the Infinity. The AA cell is arguably the most commonly used battery in existence today, so there is certainly no shortage of them and you can find them quite literally anywhere. This makes finding batteries easy. Secondly, although people love the Arc-AAA, the 4-5 hour runtime isn't enough for some users. Combining the long battery life and easy-to-find batteries of the Infinity and the outstanding brightness of the Arc-AAA was the reasoning behind this kit.

Spectrographic plot
Beam photograph on the test target at 12".
Measures 22,600mcd on a Meterman LM631 (now Amprobe LM631A) light meter.

Spectrographic plot
Spectrographic analysis of the LED in this flashlight.

Spectrographic plot
Same as above; newer spectrometer software settings used.
USB2000 spectrometer graciously donated by P.L.

ProMetric analysis
Beam cross-sectional analysis.
Image made using the ProMetric System by Radiant Imaging.


When I first assembled this kit, I couldn't get it to light up without balling up a little piece of solder into a "snake" and shoving it into the opening in my Arc's bottom. But while writing up this evaluation, I completely disassembled the kit to obtain photos, and it worked fine after I reassembled it WITHOUT the little solder thing curled up in there. I figure the hole in this foam retainer was too small to fit the nipple of an AA cell. The solder snake thing I put in there widened the hole in the foam sufficiently that it is no longer needed. When you assemble your ArcFinity kit, you can cut the hole in the foam a bit larger with a razor if it doesn't light up. Then you won't have to screw with a "solder snake" or any other add-ons like this.

More info can be found on Candlepower Forums by going to this thread.

UPDATE: 12-10-09
Performed repeat spectroscopy on this unique little light.

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