Emitter upgrade:
I changed out the emitters for 4 sliced SST40s and 3 sliced XHP70.2s. The original 7x XPL version of this light worked well, but with all the very-high-output lights coming out my desire for power motivated me to redesign the light. 7x sliced XHP50.2 would have worked great, but when most of the XHP50.2s failed I looked for other options. I predicted the SST40 + XHP70.2 arrangement would give similar high intensity and output as the XHP50.2s, but how would the beam look? The idea was to have an intense beam center that would reach out far and provide the viewer with lots of detail of the subject/target, then the XHP70.2s would provide a wider, less bright, view of the surrounding scene.
I had never mixed different sized emitters in a light so I didn’t know quite what to expect in the beam. The beam from the XHP70.2s would have about twice the diameter as the SST40 beam. My concern was whether the XHP70.2 beam would be too dim compared to the SST40 beam. If this happened it would not really help with illuminating the surroundings far out. The output of the flashlight would still be high, but the two beams would not be working well together to illuminate the same scene. The SST40s are arranged in 2s2p configuration and the XHP70.2s are 6V. The forward voltage of the 2s2p SST40 arrangement is similar to an XHP70.2 so it should get similar current to each of the XHP70.2s (i.e. each 2x2mm die should get similar current). With this knowledge I estimated that the 4 SST40 reflectors would provide around 400kcd combined and the 3 XHP70.2 reflectors would provide around 150kcd. So the larger XHP70.2 “corona” would be around a quarter of the intensity of the beam center. I figured this was close enough to the beam center intensity to effectively illuminate the surroundings of a far away scene.
On the left is the beam of the 7x XPL original light and on the right is the new configuration. The beam center intensity in each case was adjusted to be the same at the time of the pictures and the exposure settings were the same. The 3-petal pattern in the right picture is apparent because the SST40 beams are brighter than the XHP70.2 beams. As I mentioned in the first post, the plastic lens flexes and actually causes the outer reflectors to point slightly outwards, which effectively widens the beam. The beam divergence from a single reflector is greater than the divergence angle of the reflectors, so far away the beam loses the 3 petals and becomes round.
Now for some measurements. With charged Aspire 26650s I measured 35A at the tail using a 1.6 mOhm shunt in place of the tailcap (the actual tailcap resistance is 1.0 mOhms). Using ceiling bounce I estimated 23,000 lumens at start and 20,000 lumens at 5s. I think this quick output decrease is mostly due to the battery voltage falling rather than mostly heat. Based on Mooch’s test it looks like each cell’s voltage drops by 0.2V in the first 10s. Beam intensity at ~7m was 530kcd at 5-7s. With Liitokala 5000mAh 26650s at 3.75V OC I measured 19A and 14,000 lumens.
So far I only have shined it 50 or 70 meters, and the beam looks very smooth. I’m excited to try it at 300-400m. 