Extensive testing has revealed occasional flickering.
I think the specs for the control chip are for 2A max, if I read it correctly, so understandably 2.8A is outside its comfort range. Switching power supplies tend to ripple in these situations so, I guess, hence the flickering.
I have ordered some R082 and some R100 resistors to replace the R050. This should put the power supply within its comfort zone and make the light work with any battery.
Using a single unprotected cell should be fine in this light as long as you know what to look for. You can run a little test to see where you realize the cell is low and not producing as much light.
Try using the light on high and when it steps down to medium keep using it to drain the cell preferably when it’s dark. As you use it, at some point you should notice the light getting dim. When it becomes obvious it’s losing lumens turn it off and pull the cell. Wait a few minutes and measure the voltage with a DMM and see where it’s at. If it’s above 3.0v then I’d say your good as long as you pull the cell when you see the same loss in daily use. The light may even step down from medium to low that be another good indicator if it does. If you mostly use it in low mode then you probably will not get any indicator until the cell is flat.
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I prefer to have a big blast of light on hand and not use it much than to need it and not have it. I just use a lower mode for most task to extend run time.
It’s like sticking Nitrous Oxide on your daily driver. Just for the times when you need to merge into that relentless traffic. 
I agree it is possible to gauge when a light is running low on batteries, as described above.
also
the Klarus Mi1C has a battery check mode, that could be mapped for future reference
for example
on my Utorch S1 Mini, modded w sw45, the batterty check is very conservative…
4 flashes is 4+ volts on my meter
3 flashes is 3.97 volts on my meter
2 flashes is 3.87 volts on my meter
1 flash is 3.77 volts on my meter
so using an unprotected cell it is still possible to know when the battery is down to 50%, which is a good time to recharge… IF I remember to use the battery check mode (2 clicks from off)
FWIW, on my copy battery check is “3 clicks from Off”.
thanks 
and the Klarus only gives 3 flashes on full.
Have you had a chance to determine at what voltage it gives one flash?
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and to illustrate that it is Normal for the light to step down by 50% within 45 seconds, and that it fluctuates due to thermal regulation, using the same R050 resistor as the Titanium model…
here is a review of the High CRI model that uses the 219c 5000k LED (same LED that HDS calls the 3’oclock High, which they limit to 200 lumen output):
here is another runtime chart, this is the Titanium Klarus Mi1C, note how it drops quickly from turbo, and then jiggles up and down
note the comment that the TiKlarus has a low battery warning feature, a double flash every 3 minutes… this is a good thing for people who choose to use UNprotected cells.
I have now replaced the R050 with an R082 and the current has dropped to 2A. This makes the light usable with all the 16340 batteries that I have, without it dropping to middle mode. It is, of course, not as bright as before. I have also tried an R100 and the current dropped to 1A, so I went with the R082.
The problem is that the flickering is still here and it is getting worse. All I can think of is that something has been damaged during the procedures (in the beginning, since the flickering has been present.
I have ordered another Ti and a Cu, as I love this light. I have also contacted Klarus, requesting if I can purchase a driver to replace the damaged one.
As a precaution, I replaced the LED as well, with another Nichia 219b, but the flickering did not improve.
moderator007, have you had any flickering issues with the light you modded to 3A?
congrats on your ability to alter the current draw
thanks for sharing your progress
I look forward to your success
since the max continuous discharge rate for the Klarus battery is 1.5A
Im not surprised the light flickers at 2A draw
fwiw, the HDS 16340 lights are set to 1A draw, and make 200 lumens on a 219c
their titanium model costs a bit more than the Klarus, but its a Rotary 
I look forward to your modded Klarus Mi1C flicker going away with the High Drain Vapcell:
https://www.illumn.com/16340-vapcell-inr16340-800mah-7a-high-discharge-button-top.html
None what so ever, just tried it again to make sure. Klarus says its Temp protected but It looks to me more like its just a timed step down.
I didn’t time it but after about 30 to 45 secs on high it steps down but I can change the mode right back to high and it runs another 30 to 45 secs. After about the third time of changing it back to high the light gets pretty hot but it continues to run on high until it steps down and I can change it right back and it continues again where its getting to hot to hold. I don’t hardly believe its temp protected, just a timed step down.
I do not believe the different emitter is causing the flickering. I did try another, just in case.
I probably got a faulty driver or damaged it during the tests.
We will see once I get the new lights.
could the difference be the battery that moderator007 is using?
or are you already using Vapcell INR also?
The flickering is there, even with the Olight battery mentioned before.
Flickering is the current jumping around. That could be from several different things. Maybe a bad connection, a very tiny short between components some where, or a bad or shorted capacitor. If the flicker seems like it’s a constant timed thing like ever 2 seconds then I would suspect a capacitor being the problem, maybe a small short. Its being charged up then discharged causing a slight burst in current. If it’s erratic flickering then the search for the problem is pretty broad. Take a really high powered magnifying glass and have a look around for anything that shouldn’t be connected or something that may not be connected good. You can also use a DMM to check connections but that’s a little more extensive since you kind of need to know what your looking for in terms of readings and circuit layout.
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Being that the driver has not been modified from its factory condition besides the capacitors you solder back on, that be the first place I would look.
Hope you find the problem, I have had shorts that couldn’t be seen with my tired eyes but under magnification they stuck out like a sore thumb. 
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The Olight 10C battery is a very good 16340 battery, it’s what allows the S1R II to achieve 1000 true lumens, tested it in my lumen tube.
I have looked and looked again and again. I cannot find anything. I have had my fun but it is now getting annoying and is not worth my time and effort to keep looking.
If it is a short circuit, why would it only be flickering in high mode? The flickering is quite erratic. Sometimes it is there, sometimes it is not.
I think I will start with a fresh driver, as this flickering is driving me insane.
I wanted to chime in on this. I bought an Mi1C Copper version a couple of weeks ago and it flickers just like you’re describing, with the stock emitter on both the stock and a known good battery. I worked with the seller, BatteryJunction (awesome service btw) and they sent out a replacement, I got to keep the original. Well, guess what the new one flickers just the same. It has to be something with the design, as these are both brand new, unmodified lights. Its disappointing because its such a cool little light.
I’m still thinking of doing an emitter swap on one of them, maybe staying with an XPL-Hi but going for a different tint. Its still a neat thing and I don’t really notice the flicker in actual use, but it bugs the heck out of me knowing its there on brand new lights.
Thanks Gyrocks,
It is unfortunate that a few of these lights excibit flickering. I think mine may have been one of those, but as I had already modded it, I could not use the warranty.
I have two new circuit boards in the mail, coming. When I get them, I will be able to draw some concludions.
I am still waiting for two brand new circuit boards to arrive but, in the meantime, I ordered another Mi1C Ti, which arrived first.
I just replaced the LED with a Nichia 219b sw45, like I did on the first one I bought, only on this one everything is working as it should. No stepping down to mid level within seconds, no flickering.
I have tried the included battery, the Olight 10C one, and the Fenix ARB-L16-700U
I definitely had a bad driver on the first light. All’s well that ends well!
That is Great News!
congratulations
The circuit boards arrived. The faulty light got a transplant and is working fine now.
What circuit boards? How / where did you order them?