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  1. #1
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    Exclamation Limits of HID, Halogen, LED -- Long...

    In the "brightest light for under $200 thread" we were discussion limitations of certain kinds
    of light. I'm going to discuss something that apparently effects both HID and halogen lights
    (and probably not LED, *YET*).

    In that thread, a discussion on how HID lights typically require forward motion lest the lamp
    overheat was discussed. I know in my particular system (Trailtech Eclipse 13w) the manual
    says that if the light overheats it will shut off by itself to protect itself. I've not actually
    experienced this behavior though even though in commuting I've stopped at stoplights for
    minutes at a time with the light going.

    Consequences of running it as a camping light, or "impress your friends at your party with
    the incredible brilliance without a fan blowing at it" = shorter bulb life probably.

    I also read on the net a person who ran their HID for extended periods without
    forward movement caused the epoxy adhesive that kept the glass lens in place
    vaporized due to the heat, settled on the reflector for the bulb and the light
    quality significantly degraded.

    They had to find a way of using a cotton swab with electronics grade alcohol
    to polish the reflector and light quality improved but I suspect this is a very
    rare situation on very particular lighting systems.

    I also noticed in the manual for my wife's Niterider Classic Select (a 25 watt
    dual beam halogen system) it cautions very strictly about not running the lights
    for extended periods without forward motion to cool the lamps lest the bulbs
    get exposed to high levels of heat which can shorten their service life
    significantly or cause them to fail altogether.

    Obviously, halogen and HID headlight systems for automotive applications
    have been in use for years. Cars often idle with headlights running and do
    not experience these issues.

    My feeling is that the small housings for bicycle headlights lend themselves
    to the potential of high temperatures but I am pondering if some of these
    warnings were aimed at people who would stop for extended periods with
    their lights blazing or weren't cycling at all and were using them as camping
    lights or "flamethrower flashlights". I remember at least one post at mtbr.com
    where a rider left their nightrider light/battery connected in his bike bag and
    it caused a rather significant fire in the riders automobile.

    Thinking about the new generation of high powered LEDs I ponder if this issue
    won't be in effect there as well. I ran two Cateye EL300s and left those things
    on for hours with no problem whatesoever. But with the new SSC and Cree LEDs
    and some of them being run in multiple combinations in the same housing (Trinewt,
    TridenX) some of the same issues could occur I surmise.

    Has anyone really run into issues with this? I suspect these warnings just end
    up making the potential purchaser freak out unnecessarily. I know of one
    rider who commuted with a Cateye Stadium III HID for six years and had no problems of this kind.

    Your thoughts?

  2. #2
    urban biker
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    I though this was going to be long.....

    Keep in mind that bike lights are miniature forms of lights used elsewhere, so things like heating may come into play once you push the lights beyond specs and install them in a small housing, fail to dissipate heat away from the heat source, overpower, etc.. A car light is huge, so it can dissipate heat easily.

    I've used all forms of lights and heat was always a by product of light production (even more so when it comes to halogens as a good deal of power is wasted heating the filament). Low power lamps, inclusive of halogens and LEDs may not give off much heat, but the high power stuff does; look at the fins on the Dinotte 600L.

    Many manufacturers provide bike specific lights, but some firms, like TT, do nothing but take off the shelf products and install into a aluminum housing. This simplistic approach provides a product at a competitive price, but open for problems, like the one mentioned above. I have not heard of anyone who suffered the "cloudy light" problem with a L&M product. To TT's defense, they did replace my bulb when my bulb became cloudy.

    So, yeah, I have run into these problems. I'm now using a high powered LED which has the ability to run anywhere from 1 - 15 watts. At 1 watt, it never gets hot. At 15 watts, it gets hot when I sit at traffic lights and such. Interestingly, Lupine claims the light's output will vary based upon ambient temperature, so while it gets hot, I don't think the performance is degrading.

    As for your friend with the Stadium III, I have one of the first NiteRider Trail Rats and it's still going some 13 years later. The light may not be bright, but it's a simple design which equates to resilience to abuse and high dependability.
    Last edited by paulrad9; 09-22-07 at 10:15 AM.

  3. #3
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    Ham radios are very hot and have a fan that runs between transmissions and after your last transmission you should wait until the fan quits running before turning your radio off. Should we turn our lights off and ride around for a minute to cool the light down.

    This is intended to be a serious question. I brought a Stella home for demo and turned it on in the backyard. I turned it off and let it cool while doing my tests and ran my desk fan on it to cool it down afterward before putting it back in the box.
    What is better than getting your heart rate up and saddle time?

  4. #4
    Senior_Member2 diff_lock2's Avatar
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    Thats my main problem with LEDs. They heat up (and their surroundings) quit a bit. And then you start running arrays of leds on one heat sink and bam, its a toaster.

    With halogens its fine. But with leds you loose light output as they heat up.

    Keeping 15W of leds cool requires a proper heatsink. A single 3 watt will heat up its surroundings with in 10min.

  5. #5
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    So ultimately, every kind of light source has some kind of limitation imposed on it
    or "consequences" of various kinds could occur.

    Until the holy grail (for engineers) of light without heat happens, we'll just have to
    live with the various cautions and warnings various types of illumination systems
    have for their operating life.

    Sigh. No problem. I think common sense is where it all comes down. For example:
    "don't use your halogen lights to watch paint dry or use your HID to light up your
    camping tent at night..."

  6. #6
    Zoom zoom zoom zoom bonk znomit's Avatar
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    Yes, so if you are building a light system you need to think about what to do when you are stopped(or climbing at 5mph with a slight tailwind).
    For halogens you can put a 10w bulb along side your 50w blinder. Turn off the 50w when stopped.

    For LEDs you can dim them so heat is no longer an issue. In a car system there will be cooling fans.
    In general light needed is a function of speed so this all makes sense.
    If you are stopping and starting often (MTB?) you may want a bit of thermal mass in there to smooth out the temperature changes.

    HID?

  7. #7
    Senior_Member2 diff_lock2's Avatar
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    Oh and also with mr16 lights the reflector is designed to allow IR and UV to pass behind the light (heating up the housing) what i did was cover the rear with tin foil. But metallic tape would be easier.

    It really helps with keeping a plastic housing cool.

  8. #8
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by aliensporebomb View Post
    So ultimately, every kind of light source has some kind of limitation imposed on it
    or "consequences" of various kinds could occur.

    Until the holy grail (for engineers) of light without heat happens, we'll just have to
    live with the various cautions and warnings various types of illumination systems
    have for their operating life.

    Sigh. No problem. I think common sense is where it all comes down. For example:
    "don't use your halogen lights to watch paint dry or use your HID to light up your
    camping tent at night..."
    You're over thinking this. Heat dissipation is a function of temperature differential. If you ran your lights during a hot day, the temperature differential would be lower and the lamp could overheat and melt plastic bits (I would hope that the light manufacture had used the proper polymer, glass or metal bits to keep this from happening). But, since we tend to use our lights at night the temperature differential is going to be higher and, thus, the amount of heat dissipated will be greater. Some areas of the world are going to better at this than others...Denver, for example, drops 10 to 15 F when the sun goes down but Atlanta might drop only a few degrees. Ah, the benefits of dry air

    No, you probably shouldn't use your HID to light your tent...get a good LED for that. (I have one of these which has a cool diffuser to light the tent.) But on the bike, don't worry about stopping at a light or climbing hills. Rule of thumb I use: If I'm going to be stopped for more then 3 to 5 minutes, I turn them off anyway. The light is for riding and I'd rather not waste my batteries.
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  9. #9
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    I guess my main gist of posting this thread was a commenter to another post in this forum
    who discounted a particular type of lights due to these kinds of limitations.

    Research is everything.

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