Home-made headlight

Discussion in 'General Questions' started by Warner, Aug 2, 2008.

  1. Warner

    Warner Member

    I had some time today so I did some research and gathered up some parts to make myself a headlight. It basically boiled down to just 3 main parts really...the battery, the light, and a switch. I did it the easy way....I went to the auto parts store and bought a set of driving lights. I'll only need 1 of them, so I have a spare. The lights were $20 and are 55 watt and have the H3 halogen bulb in them. Knowing that these will take some real battery to power for any length of time, I bought a 7.5 AH Sealed lead acid battery and charger - both pieces were about $65. And finally I bought a toggle switch to turn the light on and off. I'll take pictures tomorrow and show you guys what I have so far. My battery is mounted from the top tube of my frame towards the front of the bike using velcro....I may look into a different mounting system - I'm not sure I like this one too much. I mounted the headlight and the toggle switch to the bracket that was being used for my front refelector. Worked great...very happy with that part of the setup. Then I waited until it was dark....REAL dark. After making some adjustments to the headlight, I can say that I'm VERY happy with this sucker! It REALLY lights up the street! I ran my bike full throttle and did not outrun the headlight or EVER feel unsafe. Thing works GREAT! I have close to $100 into the project, but I can't imagine that I could buy something that was completed already that is as bright as this with a battery and recharger for $100. I'll try to get some night pictures tomorrow night.....I'm VERY pleased with the amount of light it puts out.


    Here's the site I used for most of my research:

    PS - If you're interested, when you're in the headlight section, it's worth clicking on the picture of the girl who's standing in front of the tree....it opens the unedited photo.
    Last edited: Aug 2, 2008

  2. Warner

    Warner Member

    Here's some photos. Not dark yet but I'll try to get some that show how this light kicks butt. Next on my list of stuff to do is the following:

    Front suspension fork, which will mean converting to threadless.

    Disc brake setup up front (new wheel and brake kit)

    A friend and fellow member (ihatemybike) is helping me source the parts for the above changes.

    Install tach/hour meter (should come from Staton tomorrow)

    Here's the photos - I made myself feel better with the velcro mounting by adding some big A$$ zip ties that are rated at 175lb each:









  3. sparky

    sparky Active Member

    I want night pictures!
  4. stringer

    stringer New Member

    Slow down before you bike looks like this! :oops:

    Attached Files:

  5. stringer

    stringer New Member

    j/k looks good :smile:. anxiously awaiting night pictures also.
  6. Warner

    Warner Member

    Okay guys....here are the requested night photos. I now realize that the photos don't show exactly how good this setup is, but you get the idea. In the first two photos look at the stop sign that is a full block away! These were taken on two different streets. You can see VERY well with this light setup.

    First comparison

    Light off:

    Light on:

    Second comparison

    Light off:

    Light on:

  7. Warner

    Warner Member

    Funny guy! You're not too far off the mark, either! Hahahaha!

  8. Warner

    Warner Member

    Man, the pictures REALLY don't do this light setup justice. It's basically a motorcycle headlight on a bicycle. 55 watt halogen H3 bulb. Ah well...the wonders of digital photography I guess. It DOES light up the road real well though...

  9. jg767

    jg767 Member

    bright idea

    Seems like a reasonable price for a powerfull light. How long will it last on a full charge?
  10. Warner

    Warner Member

    That's a good question! I think the answer is "A LOT longer than it'll ever have to". I believe the battery has a discharge time of something like 20 hours. I don't think it would run the headlight that long, but I'm SURE it would last a few hours anyway, and I just clip the little alligator clips from the recharger onto the battery terminals when I bring it in after a night ride. I JUST got back from one, in fact! It's SO much fun riding at night! And that headlight is ultra cool! I like riding at night much better than in the day....esp here in the Chicago area it's so nice and cool out right now. The only thing that I like less is that I can't see my speedo (and now my tach/hour meter). Other than that, night riding is for me!

  11. jg767

    jg767 Member

    OK, warner, you've convinced me. Thanks for doing the research, looks like now's a good time to do it, the days are already getting shorter. Will definitely extend my riding hours. What are you using for a tailight?
    I have a planet bikey superflash, but I read that flashing red led's are not legal in all states, But they sure are effective, until a cop stops me they're staying.
  12. SimpleSimon

    SimpleSimon Active Member

    geez, warner, are you turning into a bag lady?
  13. Warner

    Warner Member

    That's exactly what I have...the planet bike one - superblinky or something like that.....and I put it on flash mode as well. You know it's got a mode where it just stays on solid too, right? Trust me...this headlight WORKS real well. I'm going to see if I can't get some better photos or maybe even a quick video clip. Those photos I posted are a HORRIBLE example of how well it works....

  14. Warner

    Warner Member

    Hahaha...it looks like that, huh? But you know what? I NEEDED a little weight up front, and it's not really any harder to pedal the bike and it still tops out well over 30, so what's not to like? I'm thinking I'll upgrade my front brake to a disc, though....

  15. sojudave

    sojudave Guest

    Glad to see that the light works so well. I was thinking of doing something similar after I mod my rear wheel.
  16. Warner

    Warner Member

    I don't know if there is a way to figure out how long the battery will last other than just turning it on and waiting. I'm wondering now. I'd like to think it would last for at least a couple of hours.....but I guess the only way to find out is by running it down to nothing, huh? It's REAL freakin' bright though! I had my kid ride my bike (pedaling) to the end of the street and when he was coming back towards me the light was actually annoying, like a car with its brights on. If I find out that it doesn't last long enough, I'm pretty sure they make 35 watt halogen H3 bulbs and I'll swap one of those in. That should almost double the battery life....

  17. Warner

    Warner Member

    I did some more research...and it's sobering! I haven't tested this out in practice, but here's some of the information I found about calculating my battery life for my headlight. The current setup is a 7.5 amp hour battery which is rated based on a 20 hour discharge rate. My headlight bulb is a 55 watt bulb (VERY bright). Here's what I found:

    I found this formula for roughly calculating the battery life:

    Battery amp hours X 80% divided by amp draw = approx. running time

    If this is true, here’s how mine works out:

    7.5 x 80% = 6 / 4.58 amp draw (55watt light/12volts) = 1.31 Hours

    But then I also found that with a faster discharge rate (faster than 20 hours) the amp hours are cut down DRASTICALLY. The example they gave was that if the discharge rate were 1 hour instead of 20 hours, it actually cuts the amp hours in HALF. So for my calculation above, instead of getting 1.3 hours of run time, I'd actually only get .65 hours, or about 39 minutes. Not too much. This is all based on calculations of course.

    So, what if I swapped the 55 watt bulb for a 35 watt bulb? It wouldn't be AS bright, but right now it's REALLY freakin' bright guys! Here's the same math applied to the 35 watt bulb (and remember, the discharge rate goes down quite a bit so this calculation is conservative....it should last longer!)

    7.5 x 80% = 6 /2.9 amp draw (35 watt bulb/12 volts) = 2.06 hours

    And even with the 50% penalty for quicker discharge, this still give me over an hour. I think it would be a good amount more than an hour, but that should be a worst-case scenario.

    So now I'll go buy a 35 watt H3 Bulb and see how it works!


    PS - If you're interested where this information came from, here's a link to the site:

    Last edited: Aug 7, 2008
  18. jg767

    jg767 Member

    I read something about a dimmer in sirjakesus' post, it might be better than buying a new bulb, just turn it down to what you need for a given situation. BTW, I just bought an 8ah battery (6.5 lbs.) and a set of h3 lights 60 bucks from walmart. I don't know if they make lighter batteries in this power range, I'll see if I can live with the weight.battery was only $43
    Last edited by a moderator: Dec 15, 2015
  19. Warner

    Warner Member

    Wow...my H3 lights were $20 for the pair. Yours are probably higher quality. Dimmer, huh? Hmmm....not a bad idea, then you could turn it as low or as bright as needed. I'll have to see how that works....do you have a link to his post? (he's done some cool stuff, too!)


  20. Warner

    Warner Member