Review: KD 2 x Cree XML-U2 4+10-Mode 2200 Lumens Bicycle Light (picture heavy)

Is there no thermal path between the star and the housing? I see two screws to the large oval shaped star…how does the heat get from that to the body?

Nice…pushing over 13 watts to the emitters…if it had better thermal management might even be able to push more

Possibly make a stinkpad with that large oval star (drill out the thermal path thru the dielectric, then press in some copper slugs for better thermal path from the emitters)

Still and interesting little light…

There is some thermal path over thin copper layer on the PCB you can see on the picture. Those small triangles then lay on the housing. I should make a picture. Take a look to the pictures made by Garry on very same constructed light, just different driver. There is also some thermal transfer via two screws. PCB is 2mm thick, a little bit more than tipical ones.

The power used is just enough for that small light. Better heat transfer would help of course. As far as is being used as helmet light, there is just enough light if you are using some more powerfull on the bars.

How much space is between the star and the driver, could say 1/8-1/4” of potting be applied behind the star and let harden before putting the driver in, not only adding more thermal mass but then a better thicker path for heat to flow to the body?

There is not much space left. Coil is almost touching the PCB. Then there are the wires, too. There is only some small space left on the both sides. PCB could be cut away on sides since on the other side there are TIR lenses leaving some space. Using artic alumina bond it is possible to stick there some small chunk of copper. I might just do something in this direction in the future.

Low voltage divider and thermal protection part of driver circuit. Don't know if it's very exact, but it's at least similar to what I've seen in HD-016 and another 10step driver at DX.

Thanks ledoman. I keep thinking that eventually I will need to try one of these lights,
only if there’s a 2-cell case.

You may find 2 cell battery pack at some US seller. Alternatively there is reputable store at eBay->here.

I've measured when driver turns on yellow and red status leds indicating power exhausting stages. I've measured figures at battery side. There is some voltage drop involved at higher currents. The lowest current at level 1 is probably the nearest to the voltages at the driver terminals. At level 10 there is significant difference due to voltage drop in wires and connector.

Level 1 and level 10 voltages

  • Yellow turns on at 6.15V and 6.7V respectively
  • Red turns on at 5.9V and 6.3V respectively
  • Red blinking at 5.7V and 5.8V respectively

Difference is not linear as the light starts dimming due to voltage drop below of the leds Vf.

At red blinking stage light tuns to level 2 or 3 and doesn't come up regardless if you raise the voltage. You would need to disconect the light from the power to get green status again. This is good if you're almost out of the power, but you'll still get low light for quite some time for safe return. Of course you can select lower levels by hand immediately when red status light turns on.

Thanks ledoman for your review. As I said over at MTBR, I may ditch my exact looking model from KD (though 4.2v with different driver) and get this one instead. I think I will practice the potting method on my old one though. My unit (without coil) has 6.3mm of empty space between the driver and PCB for potting. The thread on modding my light's driver (with pics of light) is here.

siata94, I have this headlamp at FastTech on my wishlist for its 2 cell battery case (buy a battery case and get a free headlamp! :) ).

-Garry

Thanks Garry. Would love to see how your modding turns out also all about potting stuff.

Battery case from Fasttech you pointed out is 2P1S (4.2V) while with this "KD2" you would need 2S1P ie. 8.4V, so no go. But it could be good for your KD version.

Sorry, forgot to point that out. It's likely moddable though to 1P2S.

-Garry

Nice review, thanks for taking the time.

Re heat sinking - it needs more. Most of these lights need more heat sinking.

I contacted KD about buying this lights driver (this "10-step user programmable" one). They will sell the driver for $8. They also reminded me that for my 4.2v version light the LEDs would need rewired to series (I appreciated hearing this from them as it showed me they had some knowledge on what they were telling me about driver replacement). If interested, you would just have to contact them and say you wish to purchase the driver used in bike light sku#S023788.

-Garry

This "10-step programmable driver is now available for purchase here: http://www.kaidomain.com/product/details.S023801 .

-Garry

^ Thanks garrybunk for getting that driver available. I just bought one.

ledoman,

Thank for this very informative review. Nice work. Although the thermal path to the housing appears limited, it might do the job fine at moderate currents. Depends on if that copper trace covers the whole MCPCB and how thick it is. Also, there appears to be some room for upgrading behind the MCPCB.

EDIT: Guess I didn't look at the pictures close enough. I just noticed this post by ledoman:

There is not much space left. Coil is almost touching the PCB. Then there are the wires, too. There is only some small space left on the both sides. PCB could be cut away on sides since on the other side there are TIR lenses leaving some space. Using artic alumina bond it is possible to stick there some small chunk of copper. I might just do something in this direction in the future.

I recall reading elsewhere that the original Gemini Duo and the earliest clones under the Yinding name had a solid aluminum wall across the middle of the housing as a thermal path, ’til early in 2014 somewhere — but those have disappeared, because people copied the outside appearance while cutting material and build time, gutting the insides. Somewhere I saw someone had just weighed the good ones vs. the recent ones — lots of material gone away.

Has anyone tracked down the early design anywhere?

This is like the ‘solid pill, hollow pill’ thing, I guess.

It's the same as the SolarStorm X2's; all the good ones appear to be gone.

-Garry

Hopefuly this Yinding is a good http://www.gearbest.com/led-flashlights/pp_124468.html.

I was talking to them to get one to test. Will see in a few days if I'm going to get one. Also I think we can get some coupon afterwards. It is just light head no other shitty accessories. If it's really good one price is not so high. Combining with this battery case can make really good light setup for helmet use.

>> all the good ones appear to be gone….

> Hopefuly this Yinding is a good

Did you decide to get that one? Any idea if it’s got heatsinking?

and

has this one come to anyone’s attention?
http://www.gearbest.com/led-flashlights/pp_71062.html
UltraFire HD-16 Cree XM-L L2 2400lm LED White Bicycle Headlight Flashlight 4 x 18650 with Head Strap Battery Charger

“Uniquefire” in the pictures

Yes I've decided to get Yinding. I'm just waiting to be sent out. It should have good heatsinking and XM-L2 U2 1A leds.

If you want to buy it including battery pack then use coupon "Yinding" for $38.04 shipped. It is currently the most wanted light there over at MTBR.