This is a great idea, its an extra safety feature for people who EDC the S21E…
Its super easy to accidentally activate the switch on the S21E.
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Simon, any idea when the 719A’s will be available to purchase in Convoy flashlights? I’m definitely looking forward to buying some ASAP 
june
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How much current do you want to achieve?
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As long as it can safely and efficiently drive a 519A and have different mode groups to choose from. I understand that higher current buck driver needs a bigger inductor, which would run into physical limit on a 17mm board with restricted height like in a S2+ pill cavity. Maybe other members will have better suggestions, but I would be happy with even a 2A-3A driver. A low VF emitter like 519A with a buck driver would net something like 30% longer runtime with the same capacity battery, which is quite substantial. I’m sure a properly rated 17mm buck driver would be very popular in the modding community.
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I mean 2A is not too bad for EDC really. If you drive a S2+ harder you just reach thermal limit quicker. I’m all for less driver power wastage and my 7135x6 is really bright enough.
Ok, I will arrange to produce some.I will reply here about the maximum current.
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Modern buck converter ICs allow pretty small solutions up to 6A at high efficiency, it should be no problem on a 17mm board and height restriction, whether 6A is adequate or not is another question, for a single 3535 LED 4~5A is sufficient, for one driver fits all, 4A or under is preferable (limited by CSLNM1).
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i will make two sample ,17mm 5A buck driver and 17mm 8A buck driver
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That would be great to upgrade my current EDC S2+ 18350. I definitively would enjoy the longer runtime.
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Good news now i need a 8a 17mm driver thanks Simón, why not a 20mm 8A driver to the m21a?
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Is it also available with SST20 660nm? Osram 620nm red does not preserve night adjusted vision as well.
Now that you mentioned it, I could definitely upgrade the 6A driver in my M21A SFT-40 to a buck. I would even be happy with a 17mm in an adapter ring.
Yes, the beam in m21a sft40 is perfect, in the m21b is very ringy, i don’t like. Imagine that beam whit 8A.
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A 20mm 8A buck driver would’ve saved me from having to sand down the 22mm to fit my M21A.
So, I’ve owned the 6A and 8A versions of the M21B SFT40, and to be perfectly honest, the 8A is not much brighter. It heats up faster, that’s for sure. It just seems like a case of serious diminishing returns above 6A to me.
I’m not sure it would be any different in the M21A.
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Yes but the 1-20-100 (5) mode whit 8a driver in m21a is perfect combo for hunting, the 20% for look around and safe batery for the long hunt time, 100 to full power when i need. Yes exist the l21b but its to big for pockets when you need to use the rifle.
Okay, I will also make the 20 mm 8A buck driver circuit.
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