First Mod. Need Help with my F13

First Mod.

So I put a H2-C in my Ultrafire F13 with a XHP50.

The light turns on High mode but won’t go to low, very low, or medium. If i double press it strobes. If I half press to normally change mode it only does a quick double flash and stays in high mode.

I beveled the driver retaining ring inner driver portion to keep from having any shorts.

Any thoughts?


Just to confirm, your XHP50 is in 12V configuration?

I did almost exactly the same thing with an h1a, like yesterday. F13 host, 50.2 (6v). Worked perfectly as-is. I decided to swap the sense resistor. R025 swapped with R020. Voiala. Only high mode and double click to strobe.

No idea what I broke, so I ordered a few more drivers and a new set of 1206 resistors.

Nothing appeared to be grounded out.

High is decently hi. Just nothing lower. I think I got over 2k lumens, which is about right.

Funny to see the same glitch.

Broke my kaidomain c8 50.2 as well, same way, but that won’t come on at all. Got a driver inbound for her as well. I tried a r100 on top of the stock sense resistor on that light. No go… killed it. Now it rests in the drawer of lost hopes and dreams. Until new drivers come…

I ran the h1c in the same host for a little bit too. With a 35hi. Ran ok with 2 26350s, but not great with a 26650. I tailstanded it, one day, for like a half hour and it went out on it’s own. Apparently the led desoldered itself from the mcpcb. Went with the 50.2 after that and never went back. Now, I just need a new driver and maybe a OP reflector.

That shelf is really thin, and I blame that for the overheated hi.

This is my led

I may be missing something. Black wire soldered to - and red wire to +. Would something be done on my side to determine the use of 6v or 12v?

are you positive it’s an h2-c and not the h1-a?

h2c outputs 12v and h1a outputs 6v

Yes H2-C 22mm.

Using the H2-C and a XHP50.2, does that require 2 cells?

Right now I’m using one Keeppower 5200mah high drain. 26650

The KD page says

So I turned the light on for a minute to let the step down timer do its thing, it only started slow flashing with no step down.

I had done this and other initial turn on without the reflector in to avoid a reflector to wire short.
I looked at both sides of the driver and there is no evidence of a short or anything burnt or other.

Whether it’s 6V or 12V depends on the MCPCB used. I think that MCPCB you bought with the LED is 6V. This could be the problem since the H2C is meant to output 12V.

If that is the problem you can buy a 12V MCPCB and XHP50 from mtnelectronics.

Fixed, sort of.

So after doing all the trouble shooting I could think of, I swapped the Xhp50 with a XHP35 HI I ordered and that did the trick. It changes modes etc fine.

Use with XHP50’s and this driver may require 2 cells, not sure but no biggie. I was kinda liking the single mode Xhp50. I have plenty more lights and parts to play with.

Thanks for the advice.

EasyB, your comment about 6v and 12v must be the answer. Here is the LED on star I picked up,

MtnE will be my answer in finding voltage specific led’s.

What would make a XHP50 a certain voltage, 16mm vs 20mm boards or something else?

Yes it does look like the answer since the driver worked with your 12V XHP35.

The XHP50 has 4 electrical contacts on the bottom, unlike a typical LED (like XPL) which has only 2. If the XHP50 is soldered to a normal XM sized MCPCB the 2 contacts on each side are shorted which configures the dies in 2s2p, or 6V. But a 12V MCPCB has 4 contacts which line up with the XHP50 contacts, and this makes the dies 4s, or 12V. You can look up pictures of the LED footprints and it will make sense.

On mtnelectronics site, just choose the 12V option when you are buying the LED and it will come in the correct MCPCB.

Got it, i appreciate all the help.

Last thing, this question seems obvious but I will ask anyway.

If I have say a XHP50, 6v driver and 6v led vs 12v driver and 12v led both running on a single cell, which combination will be brighter?


In this case, with the 6V H1A and 12V H2C, they should be the same brightness because the 6V driver sends twice as much current as the 12V driver. In general it depends on the specifications of the driver.

Buck and Boost Drivers, Testing, Modding, and Discussion (Pic Heavy)

If running single cell you may want to optimize the H2-C for 2S (“6V”) operation: #31 @ Jensen567's Entry for the 5th Annual Old Lumens Scratch Build Contest - Machine Made Category

So I ordered a XHP50.2 12v, installed it with the H2-C driver, high and strobe modes are all it will do, like with the Xhp50 6v.
Nothing else.

So I put the XHP35 back in and driver goes through all modes as designed.

I’m guessing that it’s possible that the H2-C with Xhp35 runs as designed with 1 cell.

And if I were to install the Xhp50.2 and the H2-C driver with 2 cells it would function as designed. But with the 1 cell like I’m doing then high and strobe only.

Tell me if I’m wrong on the 1 and 2 cell.


The 12V XHP50 really should work correctly with the driver like the XHP35 does. You ordered the 12V XHP50 from mtnelectronics?

Funner, what kind of 4S/“12V” XHP50 board are you using? Boards which make use of the emitter's thermal pad to connect the emitter's two 2S stages will not work correctly and I guess the problem you describe is exactly the symptom of such problem: the driver cannot regulate and goes “direct boost” over the upper 2S dices because the thermal pad is directly connected to battery cathode/negative terminal, sensing nothing over the current sense resistor (which is located between emitter's negative lead and ground). At least this is the way the H1-A driver works, a driver likely designed by the same fellows.

These are the bad boards:


Possible solutions:

  • Use a standard XM/2S2P/“6V” board and adjust the driver's output divider for 6V operation (check Jensen567's thread).
  • Isolate the board from the flashlight's body with some kickass high conductivity film. Clemence has something interesting if I do remember right.

Cheers ^:)