Sanity check my new build. M21A- XHP50.3 HI 3V -MTN-20DDm.

Flashlight Modding and DIY Parts
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It’s been quite some time since I built a flashlight. I’m still trying to catch up on all the newer technology after being out of the game for 13ish years.

Last night I built an M21A. It works great. But I’m not sure if I’m pushing it too hard or not.

Specs.
M21A with smo reflector.
XHP50.3 HI 3v 5700k from Convoy. 70cri? ( XHP50D-H-2B0-K20-A0-0-01)
FET + 7135 Driver - 20mm - MTN-20DDm
Stock tailswitch, bypassed with 24ga silicone wire from MTN.
LG-M58T battery

Build went smoothly. My first switch bypass seems to have come out decent.
Driver and mcpcb surfaces were cleaned with 99% ISO before assembly.
I used a very thin layer of Arctic Silver 5 Premium, and fixed the copper mcpcb with some better screws than what comes with the convoy hosts.
I spent a little time making sure the emitter was centered in the reflector.
The driver was fixed tightly using the included ring.
No additional heat management was implemented. ( is it needed? if so, how?)

The light is super bright. It gets pretty hot after a minute or so. Not so hot you can’t hold onto it though.
I programmed the turbo timer in guppy3drv. It starts stepping down after about 30-40ish seconds, I would guess. I haven’t timed it yet. Multimeter measures 6.55amps at the tail end.
How many amps do you think are getting to the front?

The only pics I currently have are of the switch bypass. The top left pic is after a little touchup.

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Do you think I’m pushing the emitter too hard with my setup? Or does this sound pretty normal?

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I would expect this setup to be capable of a lot more than that. Current measurement could be wrong or your driver isn’t fet-ing.

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That xhp50.3 HI can take 9 amps with good cooling. It is being under driven for sure. You can expect about 2600-3100 Lumens from it for about 20 seconds.

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Thanks guys. Good to know. I just tried it with another battery. 21700 KeepPower P2150R 5000mAh High Discharge Protected Button Top only got me around 5.2amps. I also have a couple 21700 Molicel 4500mAh INR21700P45B 45A High Discharge Button Top that should arrive in the next couple days. I’ll try those as well. My multimeter is crap. I’ll try the one I have at work tomorrow and see if there is any variance.

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You won’t get an accurate measurement using a multimeter.
You’ll need a clamp to get an accurate measurement.

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That’s good to know. Something like this up to the task?
FNIRSI DMC-100 Digital Clamp Meter Multimeter Amazon

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I’m not familiar with that brand but it looks like it’ll work.

I use a UT210E:

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Note: look at the DC current rating it’s typically much lower than the AC current rating.

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Interesting. I’ve been watching/reading a bunch of reviews on it, and people seem to like it. Still researching though.

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Edit: I didn’t mean specifically that clamp, I meant all clamp meters.
Some of them are 200A AC but 20A DC

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Gotcha. That’s what I figured you had meant.

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And are always Amps at tailcup and not at the led

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Other than a section of wire against the battery and tail end, any special gimmicks or tricks to hold the wire in place while testing?

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It can be tricky sometimes. I set my meter down in a way that the wire can still run though the middle of the clamp but I can use two hands to hold the wire to the battery / body. Be sure you use beefy wire so it doesn’t become the limiting factor.

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Thanks for the tip.
I have some 14ga silicone wire. Should work.

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Update. I got my new multimeter today.
I used a section of 14ga silicone wire to get a reading.
It was a little finicky, but i realised I had the wire incorrectly routed through the clamp.
I’m getting over 14amps.
Does that sound more inline with what I should expect with this build?

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I’d think so. Do you have other lights to gut check your meter and reading technique?

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Good call. I built up a qlite driver p60 lastnight. I had added 3 extra 7135 chips to it, which should be around 4.2amps.
I just tested that light using the same technique. Success!

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Doesn’t work that way with 46950 lights :slightly_smiling_face:

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Why not?