Does anyone here own a Convoy M21B with GT-FC40 and the included Liitokala 21700?

I have one in the mail, but have noticed some possible complaints about the light not working properly with the included cell?
And that the liitokala cell might just not be powerful enough for this emitter/driver?
I dont know if this is true or not, but figured if it is, id like to get a cell on order asap rather than recieving the light and then having to still wait on a cell in order to use it.

Maybe you also own a wurkkos ts21 and can let me know if its included cell works well in the M21B/GT-FC40?

I know all the new Convoy models sporting the GT-FC40 were just released and they are all being sold with the same cell, so I’d like to assume its perfectly suitable for these emitters/drivers.
But being so new, there are no reviews to learn from yet.

There are plenty of 5star reviews for the M21B/GT-FC40 on the Convoy Ali store, but I assume most people order it without the cell and use their own, so that doesnt neccessarily tell me what I want to know.


It’s probably fine, but don’t expect the highest power modes to be sustained well.

These 10/15A cell have decent internal resistance, but knowing how much power the driver can draw, you might drop out of turbo regulation faster than you might like, especially if the cells are cold.

I have one, it works fine. You will notice that turbo starts to flash when battery level is around 30-40%.
In the other hand, you must be careful to not drop it, because the battery gets dented very easy.

What kind of risk am I taking using it on turbo?
I dont know anything about internal resistance…
Also, I thought they performed better in the cold?

What do you mean it starts to flash? Like the LVP warning?

Thanks for the heads up. I think my Wurkkos FC12 has the same issue even though its springs on both ends.
Ive dropped it a couple times, and unless It was like this already, the positive end of the cel looks a touch dented.
Kinda worries me. That I do know what the risk is. BOOM! …or FWOOSH!

@CRC2 you are taking no risks :stuck_out_tongue:

Alright, thanks!

Yes, because the voltage drops due to high current, since the driver drains as much power as needed to keep the output level.

I can't speak to that specific battery but, the worst outcome you will see is reduced output on Turbo. High Drain cells are needed with FET-based lights to get maximum amps to the emitter and with that, the voltage can sag a bit.

Alright, Thanks.
Can this harm the cell at all?

The light will pull whatever it needs from a high discharge battery and the battery will limit the pull to what it is able to provide.

Neither will harm the battery or flashlight in any way I can think of. I run some 30A/45A (temp dependent) batteries in lights to that top out a ~4A and I have also used 3A batteries on lights that could take >10A. So far, no battery or flashlight issues.

All the lower output battery does is limit the maximum light output. On a high output battery on a device with low power needs, it just keeps the battery from warming up. Further, when you run non-Turbo modes, you are running under the Amp capacity of most batteries so, no concerns there either.

The real question is: Do you want to limit your flashlight based on the battery's ability to deliver Amps or limit the Amps drawn based on the emitter limits? Both are generally well protected.

Unprotected cells can be shorted to generate enough heat to start a fire but, that isn't going to happen with any flashlight from a reputable brand. Generally, it is done intentionally or through a really egregious hardware failure in a bad quality electronic device. Personally, I have only been around a laptop that caught fire with a failed battery pack but, that is way out of the context of this discussion.

Buy the best batteries you can, within reason, and don't worry about the flashlight or your batteries having a catastrophic or detrimental effect on each other.

Thank you very much.
This helps to alleviate much of my worries.
I still have some doubts though as I continue to read things that make me think otherwise.
But I could just be misinterpreting things, or not understanding their full context.

Well, I recieved my M21B with GTFC40 and included cell on April 27th.

The cell was recieved with 3.76v

I put it in the light and started cycling the modes.

It behaves really odd…

When I cycle through the modes, it sometimes just drops down to the lowest mode.
Never on its own. Only as I try to cycle up, it will instead, go down.

(I use group 8)
Instead of the normal cycling up and looping around from 0.1, 1, 10, 50 back to 0.1% ect
It will Instead, do something like, 0.1, 1, 10, back to 0.1, 1, 10, and sometimes will get to 50.
If I leave it on 50, it does NOT drop down on its own. (I mean, it probably would if I left it long enough, but thats not what im talking about here.)
It only drops down as I try to cycle up to the next mode.

Putting the 21700 from my Wurkkos TS21 in the light fixes this problem and everything works normal as I would have expected. Even though the Wurkkos 21700 was only at 3.47v

I fully charged the included 21700 and it still behaves odd.

I dont understand whats going on…

It’s the switch itself that’s the issue.

Try tightening the switch contact ring.

It seems to only happen with the inluded cell though.
I have actually swapped the switch a couple times, and I always put it back in nice and snug.
Im not sure this is the issue.

Ive just fully charged the included cell. 4.20v

Took the switch apart, cleaned every contact point with alcohol, and put it all back together nice and tight.

Still happens. Not every time though.

When I turn the light on, and rapid tap 3x to get to the brightest setting,(of group 8 on the 12 froup driver which is only 50%) instead of the expected “On, mode 2, mode 3, mode 4, results in, ”On, mode 2, mode 3, mode 1.

But trying a second time, works normal. (On, mode 2, mode 3, mode 4)

Try over and over again, its completely random when it co-operates and when it doesnt.

I have few of these drivers, that sometimes behave erratically. Tooks multiple taps to change mode and stuff like that. I almost believe it happens more often when you have used the light for a while. Maybe heat affects some capacitor values or something like that.

It seems to be working fine now. (with the included cell)

It was behaving pretty normal for a good while, and then just started acting up again.
I tried the fully charged Wurkkos cell, and it has the same issues with it now too.