I believe I've found the light for my bike electrical system.

Discussion in 'Electrical' started by loquin, Jan 20, 2009.

  1. loquin

    loquin Active Member


    The Element K2 flashlight. :idea:

    You can get two of them for $28 at Sam's club. (Apparently several folks have gotten faulty units with bad battery holders, but both of mine were OK.) Since I'll end up cutting off the back end of the light for the final version, I really don't care about the battery holder, anyway.

    Folks, these are the brightest LED lights I've seen firsthand, rated at 150 Lumens, per the packaging. For that matter, they're the brightest flashlight I've seen (with the possible exception of the 6V lantern types, similar to thumbnail below.) When I stepped on to the street & shone the beam down the street last night, I could see clearly for 75 yards, and was getting reflections from parked car tailights from a quarter mile away.

    It's brighter, and has a tighter beam than a 4 D-Cell Maglight. It uses the Luxeon K2 single LED 'bulb.'

    The back of the package mentioned 8 watts, but, since there are two lights in a pack, I don't know if this means 8W each, or 8W total for the two lights. (If it's 4 watts, that would be perfect for my dyno-hub. But, even if it's 8 W, it'll still work in a DynoHub/Battery system. (At speed, the Dynohub puts out 6W or more, meaning that the battery I'm using, either a 7.2 W-H SLA, or a 12 W-H Li Ion pack, would make up the difference for a minimum of 3.6 or 6 hours, respectively.

    It almost HAS to be no more than 4W each, though, as the specs call for 20 hours of light from 3 AAA batteries.

    Attached Files:

    Last edited: Jan 21, 2009

  2. Youngbird

    Youngbird Member

    That looks good to me. I think they could be cut down and installed in some oldskool "bullit" headlights and made to look real nice. Keep us all posted as lighting seems to be a real priority for safety and keeping the lawdogs at bay.
  3. loquin

    loquin Active Member

    Will do.

    These LEDs can generate a fair amount of heat, and must be heat sinked properly. As the temperature of the LED goes up, the light output goes down. As far as I can tell by looking at the LED specs, the only way to get 150 Lumens is when the LED junction temperature is at -20 C, which is -4 Fahrenheit. The LED is spec'ed at 140 Lumen at room temperature, so that packaging spec looks a little inflated...

    So, that being said, it might take some finagling to get the light inside a 'bullet' light body, but, I believe it could be done. You would remove the existing reflector head, cut off the tube at the first groove below the head (making it about 7/8 inch long) and mount the cut-off light tube to a round aluminum or copper 'block.' The aluminum block should be sized so that it could be in contact contact the chrome steel shell of the bullet light.

    And, it probably wouldn't hurt if a means for allowing air to pass by the base, without allowing water to get into the circuitry, could be worked out.
    Last edited: Jan 20, 2009
  4. sparky

    sparky Active Member

    And you can also only get 150 lumens from these flashlights for the first couple minutes, as the current draw from the batteries is not regulated. That's why they advertise that it can output light for 20 hours, but they don't tell you that it's not consistently 150 lumens for 20 hours. However... hooking these (guess you could only do one, eh?) up to a dyno might be worth while.

    I prefer the Fenix L2D Q5 because of its regulated amp draw. I thought I'd lost mine since I carry it in my pocket quite often when it's not on the bike, but just found it at a friend's house yesterday. Woo hoo!!
  5. SirJakesus

    SirJakesus Guest

    I use these. They're fackin' awesome and well worth the price.
    As a bonus you get TWO lights in a package which gives you more of a motorcycle profile at night. The pair is good for about 20mph riding in PITCH black on the rough country roads around here. I'm gonna string 4 of them up in series to my 14.8v (15.5v fully charged) LiPo.
    The heat sinks are crimped into the aluminum bodies of the light, they don't seem to heat up and run extremely bright for a long time off 3AAA's. I think with the extra airflow of a moving bicycle these will stay rather frosty.
  6. loquin

    loquin Active Member

    I ordered a buckpuck constant current regulator, I have the sturmey-archer dynohub, a 6V, 1.2 AH sealed lead-acid battery, and the light(s.)

    I need to get the battery charger circuit completed, then, hook things up.

    On a side note - these types of lights provide the most bang for the buck (efficiency) if they're not driven full-out. For instance, at 1000 mA, they emit 100 Lumens, but at 1500 mA, they emit only 130 Lumens. (50% increase in power results in 30% increase in light.) At 700 mA, they emit about 75 Lumens. *** So, if you use 2 @ 700 mA, you get 150 Lumens, but if you use 1 @ 1500 mA, you only get 130 Lumens... Plus, it's not recommended to run them at 1500 mA for very long, as it will decrease their life substantially. For a flashlight, which is used intermittently, that may not matter. But, for a headlight application, I wouldn't recommend it.

    Also, if you're going to be cutting the flashlights up for installation inside a retro chrome 'bullet' headlight, you'll probably be better off just buying the K2 Star LED assembly only, and mounting it inside the housing, in place of the existing bulb.

    (*** typical ratings, per the specs. Luxeon screens them, and can provide higher output LEDs at higher cost...)
    Last edited: Jan 21, 2009
  7. graucho

    graucho Active Member

    loquin I took your advise on the lights. So far I think there going to work for me. Plenty of beam for the amount of power consumed.
    For now im going to shelf them til spring. If your successful with your set up please keep us informed. Thanks!

    Also.... is this the style of Dynohub your talking about?

    The Dynohub was Sturmey-Archer's hub dynamo for bicycles. The Dynohub was designed as a means of generating electrical lighting power for bicycles during World War II. The initial GH12 12-volt model was introduced in the early 1940s. This was followed several years later by the GH8. This 8-volt unit was in turn supplanted in the 1950s by the lighter-weight GH6 6-volt version, which remained in production through the early 1980s. The term "dynohub" is sometimes applied generically to bicycle hub dynamos, but it originates as a trademark.
    The GH6 version produced a rated output of 6V, 2W from a 20 pole ring magnet with a stator having a continuous winding. Original headlamp bulbs are 6V 0.25A (1.5W) (e.g., CRY5) and a rear bulb of 6v 0.04A (0.24W) (e.g., CRY8). Common substitutions are a 2.4W headlamp bulb and a tail lamp bulb of 0.6W. This is different from a modern standard bicycle dynamo, though replacements can still be had.[5] One rider reports much more light with a 6.3V 0.25A (1.6W) type 40 bulb.[6]
    Rated output was reached at around 20 km/h (12mph), a rotational speed of approximately 60rpm. The name dynamo implies DC output, but as usual with bicycle dynamos (known as generators in North America), output was in fact alternating current.
    Dynohubs were offered as front hubs and as rear geared hubs. The AG was an AW 3-speed rear hub with inbuilt dynamo, while the FG was a dynamo similarly combined with an FW 4-speed.
    Hub generators were absent from Sturmey-Archer's product range from the 1980s until the 2006 introduction of the X-FDD front hub, which combines a 6v, 2.4w or 3w dynamo with a 70mm drum brake.[7]
  8. sparky

    sparky Active Member

    I'd also like to know what dynohub Loquin's got? ... and what his overall design goal is?

    Dyno recharging what size battery, regulated by exactly which buckpuck, and using both or only one of the K2 flashlights?
  9. loquin

    loquin Active Member

    The dynohub is the new version (X-FDD): rated for 6V, 3W at 12 MPH. Other, similar alternators have been measured to peak out at about 10-11 watts at higher speeds, so I could net quite a bit more power than rated.

    I'm only planning on using 1 of the K2 lights, and a 6V, 1.2AH SLA battery. (or a 4-AA NiMH battery pack.) I got the 1000 mA buckpuck (with dimming potentiometer & wiring harness) to drive the K2 at about 50% less than max current.

    I'll also power an LED tail-light off the battery, but it is low current, so I'll just use a resistor to limit the current for them. (a constant current driver would be overkill)

    I ride 11 miles each way to work, taking about a half hour to 35 minutes each way. Normally, it's only one way (and, during the winter) that I need to use the lights.

    I would like to be able to, at a minimum, ride/charge with dynohub in one direction, and ride/use battery & Dynohub in the other, indefinitely, without needing to externally recharge the battery. Obviously, if the Dyno actually puts out enough power (on average) to run the light without a net discharge of the battery, it would be icing on the cake.

    The Dynamo puts out 6 AC cycles per revolution, so, eventually, I should be able to come up with a speed trip circuit to dim the light at low speeds, reducing power to match the requirements (and the supply.) In fact, since the buckpuck has a potentiometer, I should be able to replace the pot with an FET acting as an electronic pot, and increase the brightness smoothly as the speed goes up.

    Attached Files:

    Last edited: Jan 29, 2009
  10. graucho

    graucho Active Member

    loquin, very well thought out. On paper it sounds like it should work like a dream.
    Thanks for the update. Keep up posted, I found it very interesting. graucho
  11. lordoflightaz

    lordoflightaz Member

    Should be : new version

    I hope this works for you can't wait to hear how it goes.
  12. lordoflightaz

    lordoflightaz Member

    Made it to Sam's Club yesterday. Besides the K2, for the same price they had 2 Serengeti. slightly smaller, rated at 160 lums, have a "strobe" option also as a flash light a "tactical switch" (push on let off and goes off). I stood in front of both for a while and finally picked the Serengetis probably 'cause they were black.

    Until I actually get the charger generator going I mounted one on my crossbar with 2 hose clamps.
  13. sparky

    sparky Active Member

    I'm gonna have to go check those out. I love flashlights.