I’ve had a Convoy M3 for a few years now along with a few Convoy S2+ and the M3 has never worked right. I’m running a Supernight 26650 3 7v 4500 mAh battery and the light will run on bright for about 3-5 seconds and then drop down to very dim even though the battery is fully charged. It has done this since it was new so I have never really used it. Anyone have any insight into what could be the cause of this and how to fix it?
Have you tried a different cell? Never heard of supernight cells, perhaps internal resistance is high? Tighten tailcaps and driver rings.
When you say “run on bright” is this the maximum level? Does it run for a decent time (therefore stressing the cell less) at a lower setting?
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A different cell sounds like a good idea - I’ve found that my M3 can be very sensitive to voltage drops, causing it to drop to that super-low mode if I tried the highest mode with a weaker cell or one that was too discharged.
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Ive had this happen when I used a low drain cell that was low on charge. Might be time to get a new 26650. Supernight?? Never even heard of it
Edit: is this is?
Cuz that’s maybe the sketchiest battery I’ve ever seen! And it hasn’t been made in at least a few years. It’s definitely time for a new battery
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That’s the one, I think I better buy a new one. What cell would you guys recommend?
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They are good cells. I have capacity tested them and they are all (6 of them) above the min spec. I would think they would work well with your M3. If not, there is probably something wrong with the light. But at least you should be able to rule out the cell.
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Sounds good, I ordered three of them.
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Good luck. If you have time, let us know if this fixes your problem.
As usual, make sure all of the contact areas are good and clean and that there is not excess lube anywhere to cause high resistance connections.
I probably would have gone with 21700 batteries in place of the 26650’s. Capacity is about the same and my guess is that the number of lights using 26650’s are going to be limited going-forward while options for 21700 lights will be much more.
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I’ve never heard of the 21700 batteries, I’ll have to check them out. Thanks to everyone for the advise.
Yup, I prefer 21700 cells to 26650 cells.
If 26650 cells had significantly more capacity, I would change my mind.
Here’s some nice 21700 to 26650 adapters on AliExpress (that I don’t happen to own):
https://www.aliexpress.com/i/2251832820597519.html
More development is/has gone into 21700 cells and more lights today use them. They are coming close to having the same capacity as the 26650 cells. In fact, I think I have seen some rated at the same 5500 mAh as the cells you ordered. Many more new lights are designed for 21700 cells, and you can get simple sleeve adapters or O-rings to adapt them. to 26650. But they are longer and don’t fit in all 26650 lights.
If you pick up other lights that use the 21700 cells, you can always get something to adapt them so (hopefully) you could use them in the M3. But you ordered good cells and they will do just fine in your light. 21700 is just something to keep in mind for the future.
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But he’s asking about a battery for a 26650 light
I like the 26800 with the extension tube for my M3-C.
Yes, and more than that he asked for a (direct/exact?) replacement for a specific 26650 cell.
But we often try to help in ways that were not requested at BLF… 
Helpful, yes, but often just makes things more complex for an OP than it needs to be. (I wish there was a head spinning emoticon)
It happens when battery can’t provide enough current. If it happens to the fully charged cell, it’s probably a crappy cell. I suggest you also buy a USB charging tester like the Keweisi usb tester for $3 or so. It shows you charging current and battery capacity so you know exactly the health of each of your cells. If your charger is supposed to charge a cell at, say, 1A and your cell is only charging at 0.6A, it means it has high internal resistance so it’s very old, or crappy and you shouldn’t be using it anymore.
Just a note, it could also mean the cell was near fully charged already, or a bad cable or power supply or the usb tester itself could be bad. With stuff smaller than an 18650 that’s normal too.
But ya those usb testers things are very useful. They really should be calibrated though, I have a couple of them and they all read different numbers. My favourite way to do that is to take a micro usb or usb a to c cable that you don’t care about, cut it in half, strip off some insulation so you can find the smaller power delivery + and - wires. Then strip some insulation from those and wrap them around the leads of a multimeter. Then plug that cable into the usb tester and change it to the voltage the multimeter says.
Some of them only let you calibrate to 5.00V and nothing else, so in that case plug it into a bunch of different power supplies or at different locations around the house until you find the one that’s closest to 5.00V and calibrate it then.
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So I got the new Vapcell G54 batteries in yesterday and put them on the charger overnight, this morning I put one in the M3 and it seems to be working great, so problem solved. Thanks everyone for your help.
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