Supbeam K50 V2 Mod Thread

So what would be the amp draw per battery for this light in standard form?

I’m assuming 1.5-2.0A per cell, so it’s quite manageable for any cell.

Things get a little different when modded, I’m guessing about 3.0-4.0A as the driver’s efficiency falls.

4.5A output is around 16-17 watts, and with 4 cells in series the current draw is tiny. It should be well under 2A even when the cells are dead empty.

I’m a bit new to modding drivers so I don’t really know much, but why does the driver efficiency fall as you mod it? I’m wouldn’t have thought adding a resistor or bridging connections would cause efficiency to fall so low.
Pushing 12-16A to the driver when the emitter itself will only be getting 7-8A?

With the cells in series, amps is amps. It's just at a higher voltage (more power in watts).

Max voltage is 16.8v, min voltage is 12v. High voltage low current input, to get a low voltage high current output. That's a buck driver.

Driver efficiency falls because more current through the driver means more heat, and heat is wasted electricity. The actual efficiency might not change much, but the amount of wasted electricity goes up.

That’s a good question. I’m not entirely sure, but as you push the inductor, diode, etc. beyond their rated specs, the efficiency of the driver seems to drop noticeably. When I started pushing 6.0-6.5A to my K40 and TN31, I noticed that the driver heats up pretty hot and sucks a lot of current from the cells. If the cells are almost depleted, the driver would try to suck more current for the lack of voltage. This caused my springs to heat up and lose their tension. Copper braiding them helped a lot.

Here’s a video of a voltage sweep with my modded K40. Note how the current draw shoots up to 6.69A when the voltage is about 7.5V.

Ok I see what you’re saying.
I wouldn’t have thought that the efficiency would drop to ~50%, but rather it stays relatively unchanged while heat increases from increased amount of electricity being wasted in the driver (proportionate to the increased drive levels) and of course from the LED.

The efficiency can drop, but not from 90-95% to 50%. I think something would catch fire if that happened.

I do think the efficiency does plummet to around 70-75% or below when modded.

The driver gets ridiculously hot, and the current draw from the cells seem excessive.

From the video, some quick calculations:

Emitter power: 6.0-6.5A x 4.0-4.2V = 24 - 27.3W

Input power: @0:33 3.65A x 10.0V = 36.5W

Efficiency: (24 to 27.3)/36.5W = 65.8 - 74.8%

Oh boy I know this too well… this is what fried my TK61 driver running only 5.75A. Getting a new 10A driver from Richard but only pushing it to 7.5A.
I understand that as voltage sag increases (or batteries deplete) the amps will go up to compensate [watts = volts * amps, and the power wants to go as high as possible limited only by driver or power input], but I still don’t understand why efficiency would drop that low.

EDIT:

I guess as supercooling decreases resistance in wires considerably I guess the opposite is very well possible. That makes a lot of sense now.
I remember from year 11 physics it has something to do with the atoms vibrating and flying in all directions causing collisions with each other within the wire, and by cooling them down they flow in a straight line. It would make sense that by increasing the heat energy within the wire it would create more atom collisions resulting in a higher resistance.

Hmm couldn’t hurt to keep it cool. That’s what they do in CPU overclocking - liquid nitrogen cooling but purely for setting records.

Sorry about the TK61. The driver does seem very finicky compared to the K40/K50/TN31.

The heating effect may be the cause of the decrease in efficiency.

If the driver goes from 25C to 125C, the resistance of all copper components will increase by 39.3%. This goes on a positive feedback loop as the driver tries to pull more and more current from the cells.

The components on the driver were chosen to work at the original output level with a bit of safety margin thrown in, no doubt none of it was designed to still work like stock after the output's been doubled.

The K50 with the higher 4S input voltage to start with will have more room to grow than the other lights with only 3S.

Just thinking out loud here…

Now how do we cool down the driver and wires… The only thing I can think of is using larger wires for less resistance and then potting and filling up the driver cavity completely with a good conductive material. It has to be easily removable otherwise you’d have to get a new driver every time you want to make a change. Of course the only pro to this is extended battery life by potentially 20 if it even works, but I doubt it.

Well I jumped in at the very last minute. I had no intentions of even buying the light but out of pure curiosity I sent OL a PM to see what the price was, next thing I knew I was on the list and had been sent payment information haha so naturally the easiest thing to do was buy it!

Anyway, I haven’t seen one of these pulled apart. Are the drivers similar looking to the TN31, K40, TN30 etc? Meaning we can just do the normal replacing of the sense resistors with solder and upgrading of the other bits and pieces?

Which driver did you got from RMM?

The TN31 and K40 have identical driver layouts. The TN30 has a nominal output voltage of 9.0V for the three XM-L2’s in series. Not so sure about the K50, I’m curious as to how far we can push it. I do have a gut feeling that bridging the sense resistors will be too much for the LED. (> 9.0A)

He hasn’t put it on the site yet, but it’s a new driver. He’s putting it in for me :slight_smile:

:santa: Christmas came earlier…

Not sure if this is already common knowledge or not. But I emailed Bella and asked about whether the light was glued together. She said it isn’t.