Dedomed XHP50.2 should have similar cd/lm to XP-L HD with more than double output, right?
depends on the batteries
but yes the Q8 draws about 5A per emitter
the 50.2 may draw 8-10A per emitter
I made a Q8 2S driver board
For 2S lights the A705NGT might be of interest. They are basically 7135s that are rated for 12V. I’ve just built a 6V MT-G2 headlamp based on them so I’ll be giving them a go.
For the Q8 I have a 4S design on the way for XHP35 HI with ATtiny1634 MCU and CAT4101 regulators (controlled by digipots). The CAT4101 may well be a bad choice at a high price tag, but they are easy to use for an electronics noob like me.
http://www.ebay.com/itm/10PCS-A705NGT-330-Encapsulation-SOT-89-/132216716613#shpCntId
too bad they dont ship to Germany
They don’t? Where does it say that? That’s where I got mine. Would be odd that they send to Sweden but not Germany.
Excludes: China, Austria, Germany, Switzerland
Someone else already developing a buck driver for the Q8?
Oh wauw it looks very promising all these driver plans 
Well, I got one design, but I found a different buck controller (that should be better than my first one) yesterday. I probably make a second board with the new IC.
Which IC was that?
The Texas Buck should work as a base for a Q8 buck driver, although it would not put out as much total power as the Q8 does now. Although I think we have found some better PFET’s to use compared to the one in the design.
The only practical way to make a buck driver work in the Q8 is to rewire the cells to be in 4S. There is simply not enough voltage overhead and you need too much current to make a 1S buck drive practical.
I used the ISL8117 in a 4S configuration and it should be able to output 20A.
Edit: But with that controller you need an inductor with 10uH (limiting the current capability), but now I found a controller that needs 4.7uH (with the same frequency and more efficiency, and the frequency is pretty low for less switching losses).
Hmm, a quick glance at the ISL8117 looks really interesting. I really like what I saw, that indeed would seem to make a good IC for the Q8, it is even small enough that it could fit on some smaller drivers.
Whats the new IC you found?
I am actually working on another project where we are trying to drive 15A+ on a buck so a new option would be nice.
The other one I found is an LM5145/LM25145. They both are nearly the same controller, the LM5145 has a higher maximum input voltage: 75V compared to 42V at the LM25145. Everything else is the same.
I stand corrected, I found it now… Pretty odd, shouldn’t matter what EU country they send to.
Well, I’ve been using them in one of my headlamp projects and they work alright, but the ones I have don’t draw 330mA, the consistently draw 250mA. I had to check if I got the wrong ones, but they are marked as 330mA versions. Other than that they same to be very reliable. I’ll be trying to get the 350mA versions next time.
And what IC did you choose for your project, and who is working on it with you?
So if I understand correctly one could make a driver working on 6V input and with the number of these chips control the output?
Like a 8*7135 for XPLhi, we could make a n*chip for XHP70.2?
I’ve used them for a 2S driver for the 6V MT-G2 here: Mod/build: MT-G2 & dual Nichia 219C headlamp
They are basically 7135s rated for 12V. Maybe they can handle a little more. I might give a go at seeing weather they can handle 16V for a 4S configuration (XHP-35 HI), but a buck driver would probably be a better solution.
Yeah, The Miller, that’s the idea. Up above Mike C said, “For 2S lights the A705NGT might be of interest. They are basically 7135s that are rated for 12V.”
This is getting me excited for all the Q8 modding to come.
Del and I have been working on a project for an un-named manufacture for an un-named light that would require over 30A of power. We settled on 2x 15A drivers in parallel as the best method to reach that.
We have been working with the LM3404 right now, it is a little undersized but should work with the right PFET. The larger options we found all had issues that made them impractical for flashlight use.
The ISL8117 looks interesting though, I am going to show that to Del and see what he thinks. We had not seen that one yet.
Seems like we saw the LM25145 at one point but I will have to check. We have looked at too many to keep track of lol.
LM3404? This IC has an integrated FET. Do you mean the LM3409 instead?