Yesterday I did a very experimental mod, I modded a Securitying AA zoomie (I bought it here) with a bistro driver and an Oslon Black Flat. The experiment was that the Black Flat was reflowed on a DTP-board, but to prevent electrical contact between board and pill (the thermal pad of the Black Flat is connected to led-minus), it was glued in with Arctic Alumina Adhesive. The question was if the thermal transfer to the pill would be high enough for this high power mod.
The answer is: no. The drive current on a purple Efest 14500 is over 3.5 A, with the output (flood setting) within 30 seconds dropping from 500 lumen to 275, so 45%. This is even worse than the first DQG tiny 18650 with its XM-L led on a frp board.
Still, the Black Flat is a tough led, so despite the huge temperature sag of the led, it works fine, and it has become a pretty impressive little flashlight. The numbers (37kcd at start, 27 kcd at 30 seconds) are worse than my best dedomed XP-G2 AA zoomie mods with same 18mm lens size (42 kcd steady), but the spot that the Black Flat produces is far better looking: very distinct square with even illumation, no dots.
Here’s a few pictures of the mod:
The lens was taken out and replaced by the lens from a sk68 clone (sanded the side to fit), this lens has a shorter focal length and enables focussing the spot to a sharp image of the die (the stock lens did not do that)
The stock driver is 14mm and clamped in in a weird way. I found that an exactly 15mm driver could be clamped in between pill and a tiny edge on the inside of the battery tube, it just needed sanding 1.2mm off the underside of the pill. I used a 15mm Oshpark board (made by Warhawk at the time) filled with the components taken off a Banggood X5/X6 bistro driver, except the FET that is too big, I used a LFPAK33 FET bought from Mtn Electronics.
The glueing in of the ledboard was a stressful and dirty job it was difficult to keep the board insulated, and when the adhesive was almost completely set I discovered that the holes did not line up and the board needed twisting, I barely managed to get that right. I made a 10 minute video of the process.
The led under lens in the finished light
Beam on the wall
Beam on the roof at the other side of the square, roof is at 40 meter.