See post #13, not sure if that helps?
I am on my phone now and unable to look into it properly.
This new driver is regulated in all modes unlike the old one. Turbo is not direct drive, it's 3.5A. Since you have 3 LEDs and 3 cells, input amps will be fairly close to output amps, but it is NOT in any way direct drive. Bypass the resistors if you want more and are OK with it being only suitable for use with a matching number of LEDs & cells after the bypassing (you'll have to undo that if you later want to use it with a single LED and 2 or 3 cells).
Gate for the FET on the left connects to Source by way of 20k of resistors. Itās those two series resistors marked 103 (10k Ohm) for a total of 20k. It appears that the PWM output from the MCU to the 5241 buck controller also has a 10k resistor connecting it to Source (marked 1002). I do not understand the purpose of this arrangement. When the PWM goes high the lefthand FET either becomes forward or reverse biased, but I am becoming confused. With my limited understanding I thought maybe that this was a hack to use the 5241 as a synchronous buck controller, but this does not appear to be the case.
-Side note: it may be fair to assume that the 5241a is just an even more generic 5241 than the others (LY5241, QX5241 and SM5241). Here is a listing on DinoDirect selling 5241aās as āother brandsā of QX5241ā¦ I think. oh, nevermind. Of course itās just a generic QX5241, the a/b designation relates to feedback voltage. Itās right there in the QX5241ās datasheet.
Hi guys
Can be used with 2 batteries in series and 3 series xml2?
Thanks!
No, it is not a boost driver. Output voltage will always be lower than input voltage. 2 series cells = max 8.4v, 3 series XML2 would require ~9.1v to run at 1 amp, ~10.3v for 3 amps.
:_( ā¦ok many thanks.
Well to be accurate, yes it can be used with 2 cells, and yes it can be used with 3 series XML2s, but not both at the same time. 3 XML2s would require 3 or 4 cells. I guess you could use 4 18350s?
Not come to understand well ā¦ you say that for some series parallel combination?
About of the 18350 is a good idea! but I can not use where I want to install.
Thanks
Input voltage must always be higher than output voltage with this driver, however you wire it up with whatever parts combo. To use 3 XML2s in series, the input voltage must be higher than the voltage needed to run 3 series XML2s. With only 2 cells you only have 8.4 volts input, but 3 series XML2s need more than 10 volts. That means you need more than 10 volts input, that means 3 or 4 cells (12.6 or 16.8v) input.
If you cannot change things around to get any more input voltage than 8.4v, you would have to wire the 3 XML2s in parallel, which would not be a good way to do it, since with LEDs in parallel the output current will be divided equally between them, that means it would only run at something like 1200mA per LED. If you wire them in series and raise the input voltage to 12.6 or 16.8v, the output will be 3.5A to all LEDs.
Why is it you can't put two 18350s in the place of each 18650, which would give you 16.8v input?
The most recent listing has slightly different specs: http://www.cnqualitygoods.com/goods.php?id=2123
As I mentioned, the early one I got didn't do anything different with the 'stars' bridged, it now has descriptions of what the stars do. Should be just a firmware change, the hardware is the same.
Group 1: 5modes by default (High/Mid/Low/Strobe/SOS) (no stars bridged)
Group 2: 5% 30% 100%
Group 3: 100% 30% Flash
Group 4: 100% 50%
Short-circuit two stars to change Group.
Thanks for the technical explanation 
this I already had more or less clearā¦
This part had not understood:
Well to be accurate, yes it can be used with 2 cells, and yes it can be used with 3 series XML2s, ābut not both at the same time.ā ā¦ā¦
You can use it with only 2 cells in series, as long as you only use one XML2 (or more than one in parallel). 8.4v input is greater than 3.4v output.
You can use it with 3 XML2s in series, as long as you have 3 or more cells input. 12.6v & 16.8v input is greater than ~10.5v output.
But you cannot have both at the same time in the same flashlight - 8.4 volts will not power 3 LEDs in series.
Because is a multi battery flashlight 2s 2p 18650 total 4 batteries with 18350 they would be too many volts and batteries
Four 18350s in series is 16.8 volts, this driver works fine with 16.8 volts and even a single LED. Go back to post #14 again and look at the numbers.
OK, 2S2P would need 8 18350s, but it would still be only 16.8v. It would end up as 4S2P.
Yes! I see, it works great with 2 and 3 batteries with single xml2.
I love group 2: 5% 30% 100% a pity it seems that he lost the turbo :~
Losing the turbo gave us the ability to run a single XML2 from 4 cells without blowing anything up. The old turbo only worked with 3 cells & 3 LEDs.
Anyone care to explain what exactly a DRY driver is? I guess itās not wet, but I wouldnāt think any drivers areā¦
Before my time, but my understanding is that there was a light called Dry that had a driver that went into direct drive in the highest mode. When this driver became available separately, it became a very popular driver for mods. I'd like to know why this new "version" was called "Dry". It's so different in so many ways. Is there a new Dry light that uses this driver?