How Would You: Drive 4 x XML with 3 cells in series?

The Subject header asks the Question:

How would you drive 4 x XML with 3 cells in series?

As I was browsing flashlights I came across one that had 4*XML running off 3 x 18650 In series. I started wondering how you would mod a light like that. What kind of driver would you use, and how would you wire it for maximum output.

I'm just fishing for knowledge here. I've been pondering it, and I'm still not sure.

Wire emitters in series + boost driver

Or wire the emitters in parallel and use a buck driver. Something like the HX-1175B set up to deliver around 10-12A. Assuming there is space for such a wide driver circuit.

Or just resistor mod the stock driver if possible.

Or convert batteries to parallel if possible and use one of the many many driver circuit choices out there..

I’ve looked at that boost driver and wondered if it’s as Flaky as the KD beast drivers.
Almost bought one on spec the other day.
The HX-1175B is a 7A driver. Can it be resister modded to 10-12A without cooking itself. I’ve got a few of those. I’ve been meaning to try a trim pot on one. I’ve never done that.
This is a hypothetical question. I’m just curious to see members solutions.
…and no, the cells can’t be changed to parallel.

I think efficiency would suffer somewhat with the parallel emitters and series batteries. Not saying it isn’t still the best option though, it might be.

If you don’t need to drive those LEDs super hard and you have a little space for the driver and a little change in your pocket to pay for it you can look at the boost options from TaskLED:

  • The HBFlex would run the TaskLED firmware, outputs a max of 3A, and will cost you $40 + shipping. I don’t recall whether the TaskLED firmware has an option for clicky operation, I know the default is to use an e-switch. 1.37in diameter.
  • The other option is to run a hyperboost which does not have a UI and accepts PWM dimming input. You could drive that PWM dimming input using a nanjg 105c modded with a voltage regulator and one of the many firmwares we have bouncing around here. OR the hyperboost will accept a plain ol’ potentiometer to crank the current up and down… up to a maximum of 3.2A. This one’s a little smaller at 1.3in but costs the same.

Another possible option, although I don’t think it’s a good one, would be to convert to 5x 18350’s and 1x dummy cell. Then you could run the H6Flex or H6CC buck drivers for 6.6-6.7v through the series LED string.

I’ve never been able to convince myself to shell out, but I understand that TaskLED is crème de la crème. Also I generally can’t physically fit the dimensions, heh.

I’d love to try a Hyperboost, but I can’t find any lights that it would fit into that have the right ratio of cells per emitter.
At $20 a pop, the KD beast drivers only last ten minutes to an hour, so $40 for a Hyperboost is worth it.

Good perspective on the price.

You’d be looking for a 3x18650 light with side-by-side batteries I guess, then you’d need to squeeeeze it in there.

I never heard of anyone here cook one when combined with 3 emitters. I put it in a TR-3T6 a long time ago.. Zero issues with that light. Many have used these before, and I never heard of it failing. Not sure how reliable it is with 4 emitters though. Mode changing is slow and it got some PWM whine.

The one review on KD is not that great though.

HKJ have a review on it too.

It seems so.. 11,75A in this thread.. Sometimes its higher than 7A stock too. I believe Relic38 also resistor modded his for higher output. I don't think 10A is any issue. 12 might be pushing it. Never heard of anyone kill one.

There might be a couple, but they have momentary switches which would require the Flex. I have no idea how to program one of those, or what you need to do it. I suppose these some kind of software, but since I have a Mac, I kind of doubt it would be compatable.

Every time I look at it, I think “For three emitters, why bother. A buck driver will give me 3 to 5A easy.”

You program them using his complicated UI. It’s all done using that momentary button, the manual, and flashes of the LED to indicate what’s going on.

Really! No computer program involved? Just manual presses of the switch? I can do that!

What’s the UI-UNI4 firmware it ships with for?

The LCK-Led emitter that Tom-E uses in his shockers can run 4 emitters. That is what I would use. In fact I’m going to try one when I get up the gumption in a few days or well whenever. LOL

Opinions vary but I believe this is the same driver. It only says three XML but I’m thinking it will actually run 4 if it’s the same. I have these right now and can let you know when I get around to running them.

The lightmalls driver/ LCK-LED FL-2 is a buck driver.

If you wire 4 emitters in parallel you will only get 5amp/4 emitters= 1,25A to each.

If you wire the emitters in series, it will not have high enough output voltage, so you will not see much light at all.

With 3x 18650 in series you can drive the LEDs series-parallel with a buck driver.
Like driving a MT-G2 with 3x 18650 in series.

Ouchy, what you could try is to use the FL-2 (or the similar driver you bought from RMM) and wire 3 of the emitters in series and then the 4th emitter in parallel with one of the three emitters. Im not sure how the driver behaves in that configuration though. So if you ever decide to try it, you might want to test in "bench setup" first..

You mean put the LEDs in 2s2p? At first I did not understand. Good suggestion! You can easily buck down to that current and voltage.

Yes, 2S2P the LEDs is what I mean.

I have this one and I got 4,500 lumens out of 3xXM-L2 After jumping the sense resistor. I believe the one I listed is the same exact driver but with an extra resistor already stacked. It basically became a direct drive with very low resistance. So with high amp batteries it should run 4x with no problem at all.

I know its direct drive with 3 XM-Ls in series with 3 batteries in series. I have bought more than 10 of those drivers from different sources, with different modes, with different torroids and with different resistor setups, and used them in various lights over the past year.

But its not a boost driver.. So with 3 cells in series, you will not get enough voltage to run 4 emitters in series with great output. Feel free to try...

You are probably right. I suppose the voltage would drop too much. Still I think I will give it a shot just to see. I would have thought I would see something like 4amps per emitter?

Nothing ventured nothing gained. If it won’t run it well I could always try the 2s2p.