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  1. #1
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    SkyRay 7T6 review

    Recently, Eastern web shops started to sell new bike light with seven XM-L LEDs, in various sets, with 4- to 8-cell battery or as stand-alone head:

    (Link 1, Link 2, Link 3, Link 4, Link 5, Link 6).




    As its quality seems to be higher than "average Chinese light", I'd like to share my opinion about it: perhaps, it will be useful for some of you. I've ordered this particular one:
    Super Bright 7T6 BIke Light / 7*Cree XM-L T6 Bicycle Light ( Lamp Cap Only )

    Honestly, I'm very impressed. The quality of parts and assembling is surprizingly high, especially if compared to my previous five-LED light.

    The most important thing - thermal management - is excellent here. All the LEDs are soldered on common baseplate, mounted onto massive aluminium base. Instead of thermal paste, thermal compound is used, but it's used quite properly. Layer is very thin, and it was applied immediately before mounting (excessive compound squeezed in holes), so overall thermal path is undoubtedly good. Big contact surfaces also assure that. The reflector is securely mounted with two M3 screws. Moreover, massive aluminium reflector not only used to provide mounting pressure to the LED plate (via separate plastic insulators), but also participate in thermal sinking - as it's very tightly contacted with both aluminium base and the outer case.






    Positioning of each LED in the cells is perfect. Assembled LED module and outer case both have wide and well machined contact surfaces. It's quite uncommon for Chinese light to be completely watertight, but it's the case here! Silicone button cap is not just inserted into hole, as it's usually done in other lights, but fixed by separate screw-in metal ring. And even power cord's hole is equipped with rubber boot. Obviously, glass bezel is also sealed with rubber rings. The handlebar mounting is typical, but is done more stable: shape of case's mounting surface have protruding edges preventing the mounting from rotation.





    Electrical scheme is not bad either. All the LEDs are connected in series, and powered by boost driver made of QX5241a IC, H35N03 mosfet transistor and SS34 Schottky diode. Power to the circuit is stabilized by Holtek 7133-1 regulator. Indication of battery state is tri-colour (green-blue-red-flashing red). Wires connecting the LED module have high-temperature silicone insulation. All the soldering is fine and clean.

    As the light is relatively heavy (225 g), I've replaced the mounting with self-made one:




    Power consumption seems artifically lowered. In the default condition, current in the High mode was only 2,07А (16,2 Watt), and brightness at 1m - 13800 Lux. In former lights, underpowering was probably used to compensate inferior assembling quality, but in this case, I see no reasons for that. The only thing I can suppose of, is the absence of good batteries: for year or two, Asian web-shops are selling absolute crap instead, so probably reduction of power is implemented to maintain at least marginal runtime. Enough to say, in the "6*18650 included" variant, amount of money left for the battery is around $15, so go figure...

    Anyway, I've modified the driver to increase the power to the reasonable level by changing current sense resistor's value to 0.0475 Ohm. Power component's parameters, according to their datasheets, allow for that without problems. The only thing in question is the inductor: it now works in the near to the magnetic saturation regime, and to prevent overheating I've added thermal paste and heatsink to it (simple piece of thick aluminium). Also, I've added thermal paste in all the fittings between LED base, reflector, and outer case, and replaced power cord with MagicShine one (for compatibility with my set of batteries, and because of its better quality).

    Now at full beam it eats 3,78A (power is 31 Watt), providing 21500 Lux at 1m. Further increase is possible, but at the cost of replacing some of electronic components and inductor. Most likely, it will cause problems with common cables and extensions (due to high current and voltage drop), and will require replacement of battery protection circuits with ones that can sustain such load without triggering overcurrent protection.

    As for now, heating is quite great. In the room test (25C), after 10 minutes at full beam temperature reached 64C. With household cooling fan, the temperature after the same time was just 42C, and after 15 minutes stabilized at 45C. During actual night ride, it remains barely warm - the cooling seems to be sufficient. But do not forget to switch it off at long stops!



    Beam is similar in shape to the famous MagicShine MJ-808, but have some imperfections due to the multiple smooth reflectors used. I believe, it would be great if manufacturer will ever implement version with slightly deflected optical axes of reflectors, so that individual beams will be shifted a bit around centre - that way, effective cone of light will be wider. But even in current state, it's sufficient for most offroad landscapes IMHO.

    Conclusion: the light is quite well made, and after minor modding is really powerful one.

  2. #2
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    Nice review and modification I just wonder if this would be brighter than 2 solarstorms x2 or 2 kd 880 clones.

  3. #3
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    Nice review.

    Is it possible to switch the IC with something that you can program yourself? This light only has two modes, which is not enough for a powerful light. Someone on the single xml thread did something like that, switched the control chip, but he didn't provide much detail.

    I like that mount you made. I wish these heavier lights came with these.

    Is the spot really as narrow as a 808?

  4. #4
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    Quote Originally Posted by MK96 View Post
    Nice review and modification
    Thanks.

    I just wonder if this would be brighter than 2 solarstorms x2 or 2 kd 880 clones.
    It's difficult to compare them. I have measured one SolarStorm X2 to be 14300 lux at 1m, but it is really narrow-focused light - so, perhaps two of them will produce central spot as bright as SkyRay (or even brighter), but flood will be far less IMHO.

  5. #5
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    Quote Originally Posted by varider View Post
    Nice review.
    Thank you.

    Is it possible to switch the IC with something that you can program yourself?
    Technically - yes, of course, but I don't have required hardware to do that.

    This light only has two modes, which is not enough for a powerful light.
    It depends. For me, High and Low modes are sufficient: low mode provides enough light for most road places etc, while high is used on forest trails and so on. The only thing I'd like to get rid of, is the strobe - absolutely useless in most real-life cases, and quite annoying on mode switching.

    I like that mount you made. I wish these heavier lights came with these.
    I can disclose my source of such mounts to the public!
    NEW Bicycle Water Bottle Cage Handlebar Mount Black | eBay

    Is the spot really as narrow as a 808?
    Approximately yes. I don't have beam shots on hand, but it looks similar to the initial 808 version (P7-based, not modern 808e with XM-L). But I won't call that "narrow"...

  6. #6
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    Does it use the MagicShine battery connectors?

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    No. But they're more or less compatible: the contacts are the same (5.5/2.1mm, about 10mm barrel length), but the case is smaller in diameter and does not have that special shape:



    You can connect it to the MS battery, but it will not be "locked" in place, and no protection from the elements provided.

  8. #8
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    I've just bought it (well, I bought it last July, but the Italian customs held it for 4 months -_- ) and it appears way dimmer than the 6'000 lumens advertised Could you post a detailed step by step tutorial with images on how to modify it? I'd be very grateful, thanks

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    You'll need to change current sense resistor value. On this picture, three SMD resistors to the left from MOSFET transistor (two R250 & one R330) are soldered in parallel: you'll have either to replace them with desired one(s) or add one more to obtain required resistance.

  10. #10
    Kir
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    You have to lower current sense resistor's value, there are 3 ones on the left in this picture:
    http://imageshack.us/a/img839/1750/yn9o.jpg
    Unless you know what you're doing and have experience with soldering very tiny SMD parts I don't recommend to do this, its not that easy.

  11. #11
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    Thanks a lot! Actually I have zero experience in soldering, but I'll get some help from a friend who is really good at this

  12. #12
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    Same situation here...

    So let me get this straight. The three resistors give a total resistance of 1/(1/.25+1/.25 +1/.33) = 0.0907 Ohm, and you have added a 0.1 Ohm over some of them, to achieve a total of 1/(1/.25+1/.25 +1/.33+1/.1)=0.0476 Ohm

    Does it make any difference how I add this extra resistor? Anything else good to know (I am not doing this my self, I know some skilled guys with a complete lab)

    cheers.

    Quote Originally Posted by -Archie- View Post
    You'll need to change current sense resistor value. On this picture, three SMD resistors to the left from MOSFET transistor (two R250 & one R330) are soldered in parallel: you'll have either to replace them with desired one(s) or add one more to obtain required resistance.

  13. #13
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    lofberg, yes, that's exactly what I did. As for other recommendations, the new resistor should be soldered as close as possible to the existing ones, to avoid any EM interference. Do not use coiled-wire resistors, because of parasitic inductivity: solid-state or metal film are Ok. Good luck!

    P.S. By the way, I really like this light: on my offroad night rides, it seems to be perfect. Minor beam's irregularities aren't noticeable in real life at all, while powerful spot and good spill make riding very comfortable.

  14. #14
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    Quote Originally Posted by -Archie- View Post
    By the way, I really like this light: on my offroad night rides, it seems to be perfect. Minor beam's irregularities aren't noticeable in real life at all, while powerful spot and good spill make riding very comfortable.
    Have you measured the real output in lumens?

  15. #15
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    No. Lumen measurement requires complicated equipment, and I see no reasons to buy (or make) it just for fun.

    But it's possible to calculate approximate values based on known numbers. Cree XLamp produces about 100 to 160 lumens per watt (depending from current), so if we suppose driver's efficiency of mentioned light to be ~80% and multiply obtained ~3.5 watt per LED by, for example, 120 lumen/watt ratio, it gives total output to be about 3000 lumen. Probably, some additional losses are involved here as well (like random LED bins etc), so I'd expect it to be somewhere in between 2500 and 3000 lumens.

    It seems IMHO more or less realistic, and also backed by another light of similar design - Lupine Betty R, specified (and confirmed to be) as 3600 lumens at 40 watt.

  16. #16
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    So, in other words, even after the mod it's half the declared 6k value?

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    Quote Originally Posted by purifier82 View Post
    So, in other words, even after the mod it's half the declared 6k value?
    Par for the Chinese lights. Inflated lumen values, inflated battery capacity, premium bin spec. The only thing for sure with them is the case is some kind of aluminum and there are some LEDs in it. All else is left to imagination and chance.

  18. #18
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    purifier82, if you choose the lights based on chinese descriptions - this particular one is advertised on different web shops as 1800 to 7000 lumens, so you can select any number you like.

    If seriously, 3000 lumen is pretty bright, and as far as I know this light is currently most powerful bike light you can buy for reasonable price.

  19. #19
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    Let's hope my friend doesn't fry it while soldering the new component then ^_^

  20. #20
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    Ok, report your success then, and don't forget to apply thermal paste to the light's internals.

    A bit of advertising: this is a picture of our recent night ride. The guy on wooden "bridge" uses classical MagicShine "900 chinese lumen" clone, several others are illuminating the place with similar lights of various design, and photographer has fired camera flash. The thingy on the upper-left corner of picture is me with SkyRay running at max.




    Of course, such pictures are good for ads but not for serious comparison, but you'll get some impression about how it looks like...

  21. #21
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    A picture is worth 1'000 words

  22. #22
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    Quote Originally Posted by purifier82 View Post
    A picture is worth 1'000 words
    Keep in mind that the lead bike has the light pointed away from the camera, while the nice bright one is likely pointed at the camera.

    Don't be put off by the fact that it will be less than half the advertised lumen count, that's still lots of light. IMO, beam shape is really important at this lumen level. If it is too floody, the close in area will be too bright and that fouls up your night vision to see out ahead.

  23. #23
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    Btw I've just opened it, those components are REALLY small, I hope my friend has good eyesight O_O

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    Archie,

    Independent of beam shot, lamp comparison, etc., that pic is beautiful. That withstanding, I want to see a real beam shot ASAP

  25. #25
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    Spoken with 3 different electronics expert friends, they wanna know if there is an exact model number/value for the resistor I have to add/replace (that I'm afraid I won't find in local shops...) :O

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