I’ve got the numbers in the spreadsheet, and a screenshot of the spreadsheet in the original post now. It was 76Kcd if I’m not mistaken. And the XM-L2 after adding chips was 41.5Kcd.
Shame they’ve got orange peel reflectors, could do better with mirror finished ones.
Those are bargains I mean... ....WERE Bargains!! Nice lights Dale!!
Dan.
Thinking about setting up a more easily viewed set of pics, lot of information here and it’s a bit kattywampus.
[quote=DBCstm] The MT-G2 at 2.97A is making 23.166 watts (2.97 x 7.8V from the 2 18350 under load) Dividing 23.166 by the 6.1Vf of the emitter yields an extrapolated 3.8A to the emitter. [/quote]
The two quotes above does not make any sense to me. Maybe im not following your idea of extrapolated..
If the tailcap reading is 2,97A, the emitter current is not higher. If the emitter current is 2,97A emitter Vf should be around 6,4V. Any extra voltage you are measuring are lost before getting to the emitter.
The MT-G2 should be "making" about 19,2W like I said (3A*6,4Vvf) (Vf reference).
De-domed XP-G2 R5 @ 4,27A vs domed T6 XM-L2@ 5,1A. Its quite obvious that the XP-G2 would throw better.
When you de-domed the XM-L2 you gained 54% in lux. If the XM-L2 T6 @ 5,1A had been de-domed it should see a lux number of about 64 lux (41,5*1,54) if we assume the same gain in lux. If you had used U2 bin, and driven the XM-L2 to its max (closer to 6A) it should be on level with the de-domed XP-G2 light @ 4,27A in terms of throw.
Question is, what is peak emitter current with XP-G2 and 20R cell? I have not tested that personally, but I would assume its below 5A. So if R5 XP-G2 an U2 XM-L2 were fully maxed out (domed vs domed de-domed vs de-domed) in the stock Convoy C8 reflector, XP-G2 would not throw much further (if anything further), but XM-L2 would output about twice the lumen (if not more)..
Point is, if you you drive the XM-L2 with just a little bit more energy than needed to drive an MT-G2 @ 3A. You could basically get the throw of an XP-G2, but with output quite similar to an MT-G2.
In terms of runtime, you could use a single 20R in the XM-L2 light which gives you about 1950mAh @ 5A. If you are not interested in peak output, just use a 2900mAh or 3400mAh cell instead in order to get good runtime.
In order to run the MT-G2 you need two of the Efest batteries. At 3A they are about 1380mAh (690mAh x 2), which is considerably less than the "low capacity" 20R cell.
Another thing is that with the MT-G2 light is that the low voltage cut off does not work , so unless you take out your batteries often and measure them, or keep very good track of runtime (which I find annoying) most people are more likely to only use 1000mAh if not less in order to not risk draining the batteries too much.
XM-L2 or XP-G2 with Qlite are close to idiot proof.
Just mentioning some of the pros and cons that have not been mentioned or discussed much in the thread...
That’s not the way I’ve had it explained to me to figure the current running through the MT-G2. Everything I try to say comes up sounding like an argument and I’m too tired for that.
Tailcap reading of 4.45A . 2 cells giving 7.8V while the emitter is on in high mode. That’s 34.71 watts. If the emitter is running at 6.4Vf during that power exchange. Then the 34.71 watts is being produced by 6.4Vf of the emitter, yielding an amperage through the emitter of an extrapolated (not measured) 5.42A. Which is not the same as the tail cap reading.
I don’t know why. That’s the way I’ve been told it works. Or I have forgotten something, which would not be surprising either.
I think both me an Comfy tried to explain to you in another thread that the nanjg 105C/Qlite can not boost the emitter current in any way compared to what you are seeing at the tail.
Just see this graph made by djozz, and remember that a linear driver can not increase the current from the batteries in any way. If the emitter sees a certain amount of amps, it can not see a higher amount of voltage than the required forward voltage.
The extra voltage that you seem to convert into amps is lost due to resistance in springs, switch or burnt off by the linear driver before it reaches the emitter.
I think you are confused with this because you are mixing up how a buck driver and 3 cells in series works with an MT-G2. That was probably explained to you some time back too. Unlike a linear driver, a buck driver have the ability to "convert" excess voltage into amps. (Although there are no buck drivers that can convert excess voltage into amps with 100% efficiency).
Either way, "MT-G2 + Zener modded Qlite + 2" cells is basically the same as "XM-L2 + Qlite + 1 cell". With both setups tailcap current is (basically) the same as emitter current. Excess voltage that is not lost in springs and such is "burnt off" by the 7135 regulators and converted into heat.
My K3 is easy enough to get to everything, I’ll pull the negative lead off the emitter and put the DMM in the circuit, measure actual emitter amperage and see how that compares to tail cap amperage. Last time I did that it started a whole separate argument. But I am a carpenter, a photographer, a silly stay at home dad, what do I know about electronics? Smoke and mirrors.
By the way, the formula that I showed above is my grasp of Comfy’s explanation. I looked back to find where he told me that but didn’t score, need to look some more. I’m sure I’ve gotten something wrong with my memory being what it is. And I’m almost equally sure that you’re right, I’ve been told all this before. Will have to be told again too. Don’t get old or too many miles on your machine and you’ll never have these issues.
Great comparison, thanks for the detailed info and great photos.
Don't add the capacity when cells are in series, only add the voltage. Add the capacity when they're in parallel. Right?
That's right. If you have two 850mAh efest 18350s in series you only get 850mAh, whereas if you had them in parallel you would get 1700mAh. While the mAh doesn't go up, the total potential energy output does double with two cells in series. Watts=Volts x Amps
Correct.
But my example was just made to easily compare the mAh at the same voltage. Which makes the capacity (mAh) directly and easily comparable with a normal single 18650 cell. :)
Race, I found where I’m making the mistake. I’m treating this as though it were the S2200, which uses 4 cells and a buck? driver? The math there is different. I pulled the negative lead on my MT-G2 in the K3, it’s sitting on a 1” long 7/8” diameter chunk of copper so it’s easy to get to with the head removed, I put my camera on the DMM and filmed it while I manipulated the leads and the switch. I got the exact same number as the tail cap reading at 4.74A from a pair of 20R cells with 14 chips on the Qlite. Vf was 6.63.
So of course, you were exactly right and I was misinterpreting, transposing the wrong formula to this type of set-up. Sucks having a horrible memory, really sucks. So yeah, I was doing it wrong and coming up with the wrong results. 4.74A at the tail measured the same 4.74A at the emitter, yielding 6.63Vf for 31.43Watts in my K3 with a measured 2412 OTF lumens @ 30 sec.
Thanks for making me do the hard work, finding my error. 
Hopefully I’ll be able to see by tomorrow, when my copper beauty arrives.
What can I say buddy, always a pleasure. :D
:beer:
I see, a lazy way to compare the energy provided by a 20R and the battery made up of two 18350 cells without doing the math. 
All for it, but you lost the peanut gallery. 
I would call it the correct way to compare mAh at the same voltage. Same amount of math.
I even corrected (at least to some degree,) the discharge numbers for the different cells in order to give a better picture of capacity in the two Efest batteries at load vs the 20R at load.
Except that indeed the 2 18350 cells when run in series to power the MT-G2 do not have anywhere near the capacity you stated, especially as compared to a 20R running an XM-L2.
The 2 cells working together as a battery only have 800mAh capacity, while delivering 4.45A or more to a nicely run MT-G2 at some 1707 lumens. (The Convoy C8, thoroughly tested and proven)
The single 18650 has 2000mAh capacity , while delivery 5A to the XM-L2 is only making 1256 lumens. (The Convoy C8, just built, running 5.16A)
The 20R drops fast, the 18350’s drop fast.
Neither are protected, so you’d have to watch in both cases to ensure you didn’t damage the cell. Although, as has been pointed out, the single cell driver still has protection built in and is supposed to shut down before the 20R suffers damage. Not so in the case of the modded driver running the 2 18350’s.
But isn’t it always the case? A caveat of a hot-rod is the compromises made? The car with mega horsepower, a 2 seater, almost no trunk, firm almost uncomfortable ride (pull a groin muscle, take the vette for a country ride) as compared to a still potent luxury sport sedan, nice riding, higher gas mileage with 4 doors and a trunk. Compromises. The vette makes more power, but stops more often for fuel. lol
(one more, the corvette isn’t rpm limited…you can blow it! {assumption, meaning I don’t know if this is the case or not but it sounds like a good argument} The luxury sport sedan cuts off at 135mph. Protecting you from injuring your equipment)
Yes they will.
Efest IMR 18350 V2 have 689 mAh at 3A discharge. Reference
I said it had had 690 mAh at 3A, pretty close wouldn't you say?
The samsung 20R have 1962 mAh at 5A. Reference.
I said it have 1950 mAh, which might have been closer to the truth if you pushed it to 5,2A. 5,2A is the equivalent to an MT-G2 at 3A.
MT-G2 @ 3A is just as "hotrod" as XM-L2 @ 5,2A. But with the XM-L2 @ 5,2A you get 1950mAh out of the battery. In the MT-G2 light you have an equivalent to 1390mAh (number converted to make it easily comparable with the XM-L2 18650 hotrod light).
Sure, amps/ peak output will sink quickly in both light, but the point is still the same. With the XM-L2 hot-rod light you get way more capacity even when using a "hotrod cell" compared to the MT-G2 light. And you can turn the XM-L2 light into a "normal" bright light by just throwing in a protected 3400 mAh battery.
The 2 little 18350’s are 800 mAh cells, you don’t double the amperage unless you run them in parallel! So they are supplying 4.5A with only 800 mAh capacity! (or 689.63491 under load or whatever) The 2 cell 18350 light only has the capacity of one cell, not 1390 as you keep saying.
Yes, that means they last an even shorter amount of time.
And for the record, the XM-L2 at 5A is more hot rodded than the MT-G2 at the same 5A. How far can the XM-L2 go before it fries? The MT-G2 has been tested up to 16A! I’ve personally run one at 12A with no ill effects. Try that with an XM-L2…
There you go making sense again. What I find surprising is that capacity/unit volume seems to max out in 18650 cells. Any larger or smaller and Ahr/size goes down.
All the numbers stuff is well and good, fun to argue about. But this is what matters…
damn... too bad i missed that mtg2 for sale