Testing a Cree XHP50.2 J4 3A led

Iā€™m not the one to ask something like that as 1) I do not like the XP-G3 emitter and 2) I donā€™t recall ever putting any light together that pulled such low amperage.

As far as your drawing goes, if you canā€™t put a heat sink in the opening that fills the opening then youā€™re falling short of optimization. Cut off the open air portion and leave the heat sink exposed, donā€™t pot anything. Just because something is cheaper does not make it better, most of the time itā€™s quite the opposite. If itā€™s not worth making right, itā€™s not worth making at all.

Your goals is to give the maximum heat path to the outside of the light. If you have an empty cavity then your goal is to fill in that cavity with metal or worse case potting material / silicone to give the largest heat path to all outside surfaces you can. Adding heatsinks to the inside of an enclosed space will not help you much.

For your goals, if the driver will be external, then sure, go ahead and fill in the back of the light with silicone to optimize the heat path cheaply and easily. Then close it back up for waterproofing.

That light looks like it should handle at least 15-20W without an issue based on the results with similar sized flashlights.

If youā€™re using a constant current driver then the voltage of your XHP35 wonā€™t be far from 12,7-12,9V at 1,2A. The LED voltage is current dependent. Itā€™s unlikely to get an XHP35 running at 1,2A with 14V vf, unless itā€™s broken. At higher current the voltage will automatically increase. LED die temperature also affects the voltage: higher temp lower voltage and vice versa.
14V is your input voltage. Using buck driver even under no load the V out will be slightly lower than the V in. All the components inside the driver eat some voltage to work.

Correct me if Iā€™m wrong here =)

- Clemence

I thought about the same things back when I had to mod my bike headlight. Tried to find any driver to drive XPG R5 at itā€™s max datasheet current (1,5A). As I learnt, itā€™s harder to design proper passive heatsink if I were to drive all the LEDs to their max rated current. More current = less efficient LED = more heat = more heatsink cooling needed. I ended up using boost driver and cram as many LED as I could and drive them less than 500mA each. Try not to use cooling fan, it has to be a very good long life IP66 minimum to be reliable. If you are using aluminum handlebar such as Renthal you can use it as a heatsink too.

Wait are we talking motorcycle or bicycle here? For bicycle or e-bike, efficiency should be one of your priority too.

triple 3p XPG3 quad 4p XPG3, XHP35, XHP50, or even XHP70 are the better choice if you can get boost driver. Less current - higher voltage - less heat - less power needed. A single boost driver from luxdrive is a good and very reliable driver. You can easily drive up to 40Vout using 12Vin at cooler running 350mA/LED. That will broaden your choice.
Or you can invest more, using hyperboost from Taskled, up to 80Vout with adjustable current up to 3,2A!! This is rather expensive at USD 40 but will unleash your creativity. Itā€™s also automotive rated (withstand ā€œdirtyā€ automotive voltage spikes).
Taskled Hyperboost

EDIT: Donā€™t use luxdrive unless you sure the DC power source clean from spike and pulsing. I remember I destroyed 2 luxdrive because my older scooter still used half sine DC output. You can check your front light, if it pulsing on very low RPM then itā€™s half sine DC. With full rectified DC, Luxdrive is OK. Older bike lead acid battery also fluctuates heavily when you starts the engine, or when hard downshifting (hard engine braking). Thatā€™s why linear driver isnā€™t a good choice for bikes

  • Clemence

Closer, bigger, macro pics pleaseā€¦

I did all the reflow with my ā€œdeluxeā€ DIY hotplate or heatgun.

FYI, I have two unused front light LED driver from my old scooter. Both are still working properly. If you want, I can send it to you for free (shipping cost only). Each module has three separate outputs, 3 output per module, I guess. Iā€™ll check it later. You can use the driver and throw the rest. It has fan output too.
Tried to dig into my old post in CPF but looks like itā€™s deleted by the moderator. I remember modding bikeā€™s headlight is forbidden there.


BTW: Sorry Djozz, looks like weā€™re hijacking/derailing your thread :stuck_out_tongue:

- Clemence

Derailing threads is a well-respected pastime on BLF.
Carry on. :+1:

Your never going to get a good beam pattern with that big emitter. That looks like an H4 bulb size. If your okay with a cool white color, you can use these bulbs.

They use the Philips Luxeon ZES chips and are much brighter than stock and give a perfect factory beam pattern.

My article on Bikers Oracle isnā€™t available right now as they are swapping servers. So hereā€™s a few pics. If you want more info, just let me know.

Low beam comparison on my 86 Honda vfr700.

I hope that helps.

Well I guess there wonā€™t be any pictures. Appearantly Photobucket is requiring a $400 a year fee to host pictures effective 6-28-17.

Tested. One channel smoked, sorryā€¦. :stuck_out_tongue:

- Constant current 3 channel buck driver rated for 12-15V I guessā€¦Bought from Ebay somewhere in 2013

- Designed as 2x5watt low beam and 15watt high beam (in high beam all three COBs turned on) per module

- 3 x 6V unknown super low CRI 6500+ K COB LED. Wired for 2 Lo and 1 Hi beam.

  • Each channel outputs 0,87A-0,88A. You can combine all three in parallel to get 2,64A total.

Tried with 3 x XPG 4500K bought from Sedstar (super nice and dirt cheap). Link: Sedstar 4500K XPG
These are good cheap LED with known spec, perfect for testing any project. You can use your fancy LED later

Worked fine with 3 XPG: roughly 9V, 7,9watt/channel. Could be wired for a total 3 x 7,9watt = 23-24watt total.

With 2 x 144AM (6V); roughly 10,56watt per channel the IC smoked less than 10 minutes. So you better limit the output to ~8 watt/channel. With new XPG2/3 or 219C you will get lower output power since the vf of these newer LED are lower but possibly still brighter than the good old XPG. If you can find the same IC it should easy to fix, I think itā€™s common IC found online.


If you want to use this driver you better cool the inductor, they got very warm (not too hot) with 3 x XPG. Hence the fan.
The fan got very noisy after ~1 year street use. The salty balinese dust sucked rubbed the exposed plain bearing.

@JasonWW: We never wanted to use those badly designed LED engine. I offered Stormrider the driver, not suggesting him to use it as is. Itā€™s an awful kind of LED lamp indeed. I bought it during the dark ages when anything brighter than halogen bulb attracted me. And no, I really hate cool white headlight, no matter what CRI they are.
As for the image hosting, try Flickr. Rather complicated but allows you to store very high quality images complete with copyrights protection and rich features.

Flickr seems popular. Iā€™ll just go around the forum looking for pictures that still show up and see what host they use. :wink:

For me, anything less than cool white looks dingy. Like old style incandescent bulbs. I canā€™t stand it.

Cool white for me is anything over 5000K. I prefer to work under 5700K high CRI. Driving is another thing, on whitish cement road or behind white painted car, anything above 5000K irritate my eyes. Try tailing a white ambulance with CW HID on a empty twisty country side road (no street lights).
But yes, lower than 4000K everything looks not so good (for driving).

- Clemence

Yeah, like I mentioned in post 229, I have an old 86 Honda vfr700. Itā€™s got LED headlights (and just last week, LED tail lights).

Reminds me of the old pocket rocket: Honda RVF400
Revving up to 15000RPM each upshifting, with 4-1 pipe sounds like a crazy mosquitoe from afar. The whiney timing gear sound also very distinctive. Those were the daysā€¦

Yeah, thatā€™s the smaller, and slightly newer version of my bike. Great V4 engines.

No, I did not.

I mainly donā€™t want to sacrifice the factory beam pattern just to get a slightly warmer tint. Thatā€™s what happens when you move to an xhp50, xhp70 or XML size emitter. Good beam pattern with a sharp cutoff line is my highest priority. The second highest priority is being noticeably brighter than the stock incandescent bulb. Then a lowly third is a good enough color temperature.

The first two can be accomplished with a little hunting around and maybe small modifications. Then youā€™re stuck with whatever color they give you. Usually thatā€™s cool white.

My first set of car LED headlights were cool white with a tiny bit of blue, but my current set of headlights are actually a more pure white without any traces of blue. Color reproduction is quite nice.

Oh well, just trying to help.

That looks easy enough, heatgun or hotplate will desolder the LED without ruining the rest of the components.

  • If itā€™s MCPCB then hotplate is the easiest way, at 240C bed temp all 60/40, 63/37 lead and SAC305 leadfree solder will melt completely without excessive yellowing of the solder mask. Donā€™t let the board stayed too long on it, youā€™ll yellow the masking ink.

- If itā€™s FR4 board preheat slowly no more than 120C for 5 minutes on hot plate followed with heatgun ontop. Make sure you put a thermocouple fixed on the board so you can monitor the temp (240-260C) is max reflow temp according to many componentā€™s specs. Place your heatgun gradually closer as the blower could blew the components off the board. When you start to smell burnt epoxy shut the heatgun off or move it farther away from the board.
The better way for FR4 boards is Infra Red top heater oven such as found in your toaster. The resin-fiberglass matrix has very low thermal conductivity making hotplate technique harder and requires longer preheat time.

- Clemence

Haikelight wrote somewhere they fixed the green tint shift, any idea how?

Am I correct when I say:
4 x XHP50.2 driven at 6A each (so in a Q8 like configuration 24A from the driver) produce 16K lumens
?
I have an idea for the future Q16 and 16K lumens would be so awesome but I would not want a green tint shift.

coarse OP reflector?

ah, could mbe, i have not seen a review on the updated version