The LG HG2 is a good high drain battery, so you donât need to buy any other.
Thank you for good advice, yes I read brown HG2 is good for high current. Good to know you recommend it. I will test driver out and post photo of performance. Now I am using default mode (4.2 at Turbo), with candle flicker mode also, but the flicker is a bit too âstrongâ, like a windy candle. I will test more later one with higher mode at 5.5A. Right now I am using spring tailcap. Will add bypass wire next. I am wait for pcb for gfs16 mosfet switch to upgrade.
That âbuttonâ you made from a cable terminal is a good idea. But, it wonât perform nearly as well as a solid piece of copper. As long as youâre happy with it, thatâs all fine. But, I thought you should know that will be a source of resistance in the circuit.
Hello Mr. David! Yes I agree with you but I do not have same skill and copper to make as Moderator007. I think the resistance is not as good, but very much better than spring or wire bypass because it is still essentially a heavy copper pipe. This cable terminal is design for more than 15A so I hope it is OK! I try my best to sand the top and bottom as flat as possible.
15A will be absolutely no problem from it.
Heck, 40A will not a problem for it too, so you should not be worried 
It should be a very minute difference. A couple a days ago, I punched in the dimensions of my copper stud in a online calculator and it spit out it was good for over a 1000 amps with its short length.
Glad you got everything working clientequator. Looks good 
.
Here is my first impression of gxb172 with my XHP50B J4 led in Convoy S2+ host and lg hg2 battery.
Some photo of flashlight in use.
Beam on wall:
Low mode:
Outdoor with clear air no fog, on turbo (light is extremely bright) - now 5A setting
First observation:
- Flashlight is extremely bright! I am now using default mode at 5A maximum, I will adjust for 5.5A later on with X1 X2 jumper and measure current. Single flashlight is enough to light up entire room!! I have never seen such small flashlight to be so bright.
- Lowest mode is quite dim (good), useful during night time without be too bright for night-vision
- I notice flashlight has very-very short bright flash during turn on, but only during dim modes, likely not problem
- Flashlight get hot extremely quickly! It seems thermal control works well, and automatically dim light about after a minute, however, thermal control will also increase brightness (all the way to maximum!) if you cool flashlight (such as when put in cold tap water!!)
- Although front get very hot, flashlight body is still ok to hold.
- I did not notice thermal 'turn off' or any high frequeny sound as report by schizobovine. Moderator007, did you notice high frequency sound? The flashlight is silent at all modes.
- XHP50B beam is nice in the middle but slight yellow/green around center hot spot
- Mode memory is simple and work
I have not encounter any flashing error code yet. I hope to do more simple test soon, such as with low battery.
Now I understand schizobovine using XHP70, feeling motivate to turn up current and change to XHP70 for more light!!
Its terrific to see you achieve what you have so far clientequator. Well done.
Very nice results here!
I havenât experienced any whine in any of the 3. The flash is present at turn on and going from turbo back to low in my drivers. Its not a really bright flash, just a short flicker like change. I played around a little with the 3rd driver I built with my bench power supply. I need to make a better hook up setup for this driver to my power supply. 15 amps on the input side of the driver loses a lot of voltage threw long or small wires and not very accurate, every little bit counts. I gotta beef up the setup.
When I purchased this 50 volt 15 amp supply, I never thought I would need more power than that. I was wrong, the GXB17 will draw more than 15 amps. 
Also to moderator. Well done.
I will do current measurement soon if I can borrow clamp meter.
Idea to use XHP70.2...
Moderator007, maybe you can get more light out by using better XHP70.2. I do not have way to measurement of lumens.
The xhp70.2 will make more lumens but with a much larger hot spot in such a small reflector. Even with the xhp50.2 the hot spot is large versus a xpl. If I find a suitable host that excepts a 21700 battery with a larger reflector, I may jump up to the xhp70.2. I already own a modded convoy L6 with a xhp70.2 So I kind of know what to expect from output.
I make current measurement today. So far after playing with flashlight for entire day, no problem yet!
For low values, I use multimeter in Amps setting. For turbo mode, I use wire and extech clamp meter (but 2.5% error+some digits). Battery used is LG HG2. I also solder J1 and J2 to test turbo mode at 5.5A. Default turbo mode is 5A. According to Loneoceans current chart of current to 6V LED, here is the tail-cap current I measure:
- Moonlight (<10mA) - 12mA
- Candle (no rating) - 20 - 40mA? Jumps around
- Low (50mA) - 72mA
- Med (250mA) - 390mA
- Bright (1A) - 1520mA
- Turbo (5A) - 11.2A (clamp meter)
- Turbo (5.5A) - 12.4A (clamp meter)
Be careful - tail current only applicable to my battery, if you use better battery, current may be less. It seem like with changing resistor or firmware, much more current can be achieve!
However at 4V battery voltage, 12.4A is already 49.6 watts!! 
Please let me know if anyone want to know more test.
Review:
Overall this was very interesting project to solder. Although I have soldering experience, Gxb172 was still difficult to solder together, but easier with practise. I recommend using usb microsocope or magnification during soldering, very small solder tip, very thin solder wire, and hot air. For mistake, thin solder-wick is the best.
I also suggest using flux pen and needle tweezer. For cleaning, I use cleaning alcohol and cotton swab. Solder for temperature IC is most difficult because it is very small, so I suggest using no solder, only flux. High heat and low air speed. Inductor is hard to solder, but just keep at ~270C air heat for a while and it will solder.
Finally, before assemble I suggest to test with multimeter to make sure no shorts, then test before putting into flashlight host.
For program, I don't know of easier way than using pogoprog, but you can also use thin wire soldered to programmer. I use Atmel ICE, so I have no idea about USBASP, but moderator007 has used it to program so it will work.
Difficulty - 7/10
Cost - 8/10
Brightness & result - 9/10
I hope to be able to get firmware to change for even more current, or I may have to do resistor mod
I added a .05 ohm 805 resistor stacked on top of the .01 ohm for .0083 feedback and runâs slightly over specâs . My meter read around 15 amps with a 30Q but it could be more than that.
My Fluke 87V is only rated for 10 amps. I donât have a DC clamp meter. Increased light out put a little over 300 lumens.
Nice write up. Iâm really hoping we can inspire some others to follow. For a single cell light, itâs a beast of a driver. 
Have you thought about using a DIY current shunt?
Using something like a 5-10mOhm wire would be good for measuring such high currents.
This is how I actually do it.
I havenât tried that yet as I feel the 87V is pretty close. My numbers before the resistor mod, pretty much resemble clientequatorâs at each mode and jumper setting.
I may end up buying a clamp meter, but I think I have hit the upper limit with this driver. If my math is correct Iâm guessing around 55 watts in.
I want to post update here to show my finish Gxb172 flashlight combine with Gfs16 mosfet switch and led tail light!
After finish my Gxb172, I build the Gfs16, my post is here #134: https://budgetlightforum.com/t/-/50404?page=4. Here are photos from this project:
Review for gfs16:
This project is easier to solder together than Gxb172. The hardest one is soldering the tiny mosfets on the led board. The rest is easier than Gxb172. I am not sure why schizobovine have problem with battery, since mine work first time.
Same as Gxb172, I recommend to use magnification to solder with smaller solder tip, thin solder wire. I only use hot air for the lfpak33 mosfet.
Before assemble, I suggest to make sure lfpak33 have no short, battery have no short, and led light system voltage working with power supply. For me I use oshpark 0.8mm pcb for both and they fit Convoy S2+ good.
I recommend the hobby maker to order more tiny mosfets before you blow them on the floor, and I recommend making sure you buy the correct Convoy s2+ light to make sure it fit the stainless steel switch! Make sure you handle tiny battery carefully! Also I use very thin wire (awg30?) to solder + and - pad together. I make sure I keep the switch screw tight, but not overtight to prevent pcb from breaking because it is not as strong as aluminum washer.
Difficulty - 6/10
Cost - 5/10
Result - 9/10! Very nice! I remove one point so it is not perfect so loneoceans can motivate to improve it 
I recommend loneoceans add more led on the tail to make ring of light, but I understand how it may have no space since need two bank of leds, and any smaller is harder to solder.
Final bonus photo of S2+ in snow! I am disappointed because it didn't melt all the snow 
, but flashlight make the snow light up very bright from inside!
After using this light a while, I think actually I mostly use 'low' and 'medium' mode the most. Moon light mode useful during night-use and the ramp help to prevent blinding me. The turbo is too bright and only useful to show off to friends, but still a fun project!
Big thank and appreciation to loneoceans for this cool project and for everyone here who also make their own and inspire me to build this successful project!!
Nice build! I like that snow pic! 
Thanks for this thread, I had been on Loneoceanâs site and the gerber files dont seem to be there nor the firmware, etc only the schematic.
Ive found a github link for the firmware, but still reading up on whats required for the build.
Are all the modes set by jumpers? You dont need to modify the code to set your custom brightness levels?
Im up for the challenge to build one, ive done SMD work before, but I will get a bunch of boards made from JLCPCB, they also offer an SMD assembly service, so if thats cheap enough, I may as well just get them to make me a bunch of boards.
Loneoceans also is the same person who designed the universal driver 2.7 revision for a DRSSTC, (musical tesla coil) I have built one using his driver board and it is of excellent design.
Thanks Loneoceans if you are reading this 