Hello everyone!
I have a convoy S2 and it works pretty fine when the battery is charged. It has 6 ICs 7135 and can handle maybe 2A. But after several minutes of use the current drops to 1A because of the voltage (7135 only limits the current).
Where can I buy the driver for my UV flashlight? Maybe somebody from EU has it and ready to sell it to me? 
As far as I know there is not a great single cell option for UV LEDs. It would need to be a buck-boost driver I think since the battery voltage will cross the LED voltage during discharge.
You could do 2 18350 and a buck driver.
Or you could find an LED with a lower Vf to increase the regulation time. Also you could use 3 LEDs in parallel to lower the effective Vf, but that would be more difficult. And bypass your springs to reduce the voltage drops.
Look here and in other djozz tests for different UV LEDs and their Vf.
Thanks for the reply. I have LEUVA33W70RL00 LED.
I’ve checked the link, they all drop current very fast when it’s below 3.8V.
I have an idea, a work-around. Is there a circuit which can boost the voltage to 4.2V with the size of a protection PCB
It will increase the size of the battery a little, but there is enough space to squeeze the spring.
Here is a rectalgular shape.
I think it’s not a good idea. 2A, maybe 70% efficiency of two drivers. 30% goes to heat.
UVs are funny finicky things. If memory serves that led is great in terms of output with considerably lower Vf than many (I think it was a small step up from the previous LG that was popular…I have one of the previous and a Nichia).
Off the shelf I’m not seeing anything in a 17mm that does what’s needed here but I’m curious about this one from the LHT store. Boost that indicates 4.2v on lithium but not sure if that’s just straight normal or if it’s actually boosting/constant current as it seems to for other configurations. https://www.aliexpress.com/item/32760084359.html
There are a couple ok choices for a buck if you wanted two 18350 like EasyB said….but with the derating curve and low heat dissipation of the S2 host and lower capacity of 18350…not sure it would be an improvement overall.
This BD-39 has current choices (many drivers are putting out more these days, would cook the UV). 1.5A is only single mode, 2.2A has mode options: https://www.aliexpress.com/item/4001251200171.html
CF-FX….2.2A: https://www.aliexpress.com/item/32762099921.html
Even though it “can handle” that amperage, personally I don’t think I’d want to run mine that high especially in a host that can’t take much heat. I guess if it peters out you can always replace the emitter “early” but they aren’t always easy to come by, or not in good bins. The difference in output between 2A and 1.5A is pretty minimal really, so if you don’t mind running it lower and it’ll serve your needs, you can enjoy a bit more run time and lifespand.
Now…off the top of my head I’m not thinking of any, but if someone makes a boost/buck for a 3v emitter in a smaller 17mm board, maybe you can contact them to buy the driver separately (talking bigger mainstream light brands here, so to speak). Seems like most of the fancy drivers are on larger boards or amazingly tiny ones.
Keep in mind the pill space, too…can’t recall how high you can go on the top of the driver for S2/S2+ one of these drivers is 12mm high.
If stepping up to a 21700-size hose like the S21 is an option, that would open possibilities.
Thanks for the answers. I was tempting to create my own PCB, but now I don’t have much time for it. I think I’ll stay with my linear driver and next time will buy something with higher voltage and buck-drivered.
Keep in mind that UVLEDs are very finicky about being overdriven. Unlike white LEDs, they go pouf very easily.