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  1. #1
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    12 volt light on a bike?

    i was wondering if it would be possible to use a 12volt light on a bike. i want to use a 12 volt light on my one bike but don't want to be carrying a 12 volt battery everywhere. i've tried using google and not found much.

  2. #2
    Gimme back my gears!
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    Go to a battery store (or online) and pick up 2x4 AA battery packs. the math is 1.5 volts x 8 = 12v

    Wire them however you want and stick them wherever you want.
    Quote Originally Posted by hao View Post
    Let's not go crazy here, you make him sound like the Forrest Gump of BF.

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    Gimme back my gears!
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    I carried a near 30 pound battery around yesterday on a bike ride (40 pounds total in backpack) to power 180 led lights... something, that while I got a lot of compliments... is something I will never do again. I was worried they would drain the battery and I over compensated by many many sizes too large!
    Quote Originally Posted by hao View Post
    Let's not go crazy here, you make him sound like the Forrest Gump of BF.

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    4 18650s in series is 14.4 volt. 8 1.5 AA in series is 12 volt, or 10 1.2 volt NiMH AA in series, that's also 12 volts.

    Using modern LEDs with a step down setup, 14.4 volts is enough to power 3 Cree XP-Gs for 900+ lumens.

    Here's an example of a 14.4 volt 18650 li-ion. 13 ounces.



    http://www.batteryspace.com/customiz...fuelgauge.aspx

  5. #5
    Seņior Member ItsJustMe's Avatar
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    Sure, using 12 volt lighting was pretty much what everyone did up until about 3 years ago when really bright LEDs became the standard. There are still people using them. I have my old 12v halogen in the garage as a backup.

    If you want to run a 12v light, you pretty much need 12 volts. But as people above have said, there are many ways to get 12 volts. I started out with an 8 pound lead acid battery, but after a year I bought a 14.4v NiMH bottle battery. These days I'd use LiIon.
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    LED are great but i have not found something good enough to light up the path in front of me when i'm biking trails at night. my friend has a brand new Sealed-beam halogen headlamp from his old jeep that he said that i could have and i was thinking it would make a great light if only i could power it. i know it would require a lot of power and would drain small batteries fairly quickly. i was hoping i could use a generator. i have a 6VAC generator but obviously that would not be enough on its own. is there any way i could use the generator to charge some small batteries?

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    You could use a 12v 4.5 AH sealed rechargeable gel battery. It's the type that they use in house alarm backup systems. It weighs about 3 lbs and you can get a charger from Z Battery or any other battery supplier pretty cheap.
    I use a 6v 4.5 AH battery that I carry in my small trunk bag. Works great.

  8. #8
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    Quote Originally Posted by crazzywolfie View Post
    LED are great but i have not found something good enough to light up the path in front of me when i'm biking trails at night.
    Um... no. You obviously haven't seen the newer LEDs (I'm not talking about the 5mm leds).

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    if i have not seen the new LEDs then show me. i have not found a LED bike light that works good for me. LEDs make great flashlights but i can't find a bike light that creates enough light when i am on the trails at night. that is why i want to use a 12 volt light that i knows creates enough light. i just don't want to carry the heavy batteries that go with it.

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  11. #11
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    some of those lights might work for what i need but the price for something like that is way more than i want to spend on a light for my bike.

  12. #12
    Seņior Member ItsJustMe's Avatar
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    The MagicShine 1400 should light up most anything. I find the 900 good enough but I'm on the road. The 1400 is about $125. I think by the time you get done dinking around with stuff, if your time is worth anything at all to you, the $125 isn't a bad price.

    My MagicShine 900 definitely puts out WAY more light than the 20 watt halogen that I used to use. Heck, my P7 flashlight at $60 with charger and battery puts out more light than the 20 watt halogen.

    The only reason I'd go for a halogen these days would be if I ABSOLUTELY could not afford $60 (for a flashlight and charger), but I could afford $50 (about what I think it would cost to build a cheap halogen with battery and charger). Even then I think I'd see if I could find some bottles to return to make up the $10, because a flashlight is so much more convenient.

    The flashlight doesn't have uninterrupted runtime though. For that I'd have to spend $85 and get the MagicShine.

    MagicShine 900

    MagicShine 1400
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    thanks for the links. those lights look great but there too expensive for me. i might just try cutting up a 6 volt flash light and sticking a 4.5volt bulb in it so that it should work with my generator

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    Quote Originally Posted by ItsJustMe View Post
    The only reason I'd go for a halogen these days would be if I ABSOLUTELY could not afford $60 (for a flashlight and charger), but I could afford $50 (about what I think it would cost to build a cheap halogen with battery and charger). Even then I think I'd see if I could find some bottles to return to make up the $10, because a flashlight is so much more convenient.
    You could cut that down to $35, for flashlight, charger, and battery.

    http://www.dealextreme.com/details.dx/sku.39359
    http://www.dealextreme.com/details.dx/sku.936
    http://www.dealextreme.com/details.dx/sku.5776

    If you can't afford that, well, you shouldn't be riding a bike at night.

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    thats not too bad of a price for a bike light. i might order one in a week or so when i get some extra money for one. i already spent my extra money for this month on a small flux core welder.
    Last edited by crazzywolfie; 08-24-10 at 12:49 AM.

  16. #16
    Formerly Known as Newbie Juha's Avatar
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    Regarding generators, the only 12V dynamo system for bikes I know of is made by Busch & Mueller, http://www.bumm.de/index-e.html (click "Catalogue" on the navigation). But a dynamo based system is definitely NOT good for off-road riding. I'd definitely look into battery operated lights.

    None of the cheap flashlight type designs are "bike lights". No design effort went into them to make them bike specific, apart from making or rebranding a handlebar/helmet mount. Fortunately, in your case (riding on trails) none of that matters much. A simple cone shaped beam is probably more useful to you than the more expensive shaped beam designed for biking in traffic.

    When you buy a light, remember to budget something for a reasonably good charger and batteries. Charger and batteries will likely last longer than the light, especially in off road use.

    --J
    Last edited by Juha; 08-24-10 at 07:39 AM.
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  17. #17
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by crazzywolfie View Post
    if i have not seen the new LEDs then show me. i have not found a LED bike light that works good for me. LEDs make great flashlights but i can't find a bike light that creates enough light when i am on the trails at night. that is why i want to use a 12 volt light that i knows creates enough light. i just don't want to carry the heavy batteries that go with it.
    If you want a light that creates enough light for riding on trails, you definitely don't want a generator powered light. The reason that there are so many battery powered lights out there is because they are the only ones that can put out the kind of light you want...and need...for off-road riding. You, as a cyclist, just can't put out enough power to run a very bright light. For example, 3W of power is about all that a 6V dynamo can put out. You friends light requires 55W to power it. You need 4.5 amps to power that 55 W light at 12V. You just can't pedal that hard.

    If you want bright lights, you'll have to carry around some kind of battery. That doesn't mean you have to use lead acid. There are lighter weight batteries out there. NiMH is still a pretty good battery and it's charge to weight ratio is reasonable while it's cost is very good. Li-ion batteries have a higher charge to weight ratio but they are still expensive batteries.

    If you want more light, you can always go back to halogen. It's not as efficient as LED but it can be made brighter. Look here and here for details. However, for the cost, the Magic Shine lights are hard to beat. My team and I used them for the 24hr of E-Rock this spring. They are very good, only a little dimmer than the halogen and much have much less weight. For trail riding...and commuting for that matter...get at least 2. One for the bars and one for the helmet. Even if you run halogen, you should have at least 2 lights.
    Stuart Black
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  18. #18
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    thanks for the advise and info. now that i know what i'm kind of looking for now i have been searching and found a few in my price range right now and was wondering what you think.
    http://cgi.ebay.ca/ws/eBayISAPI.dll?...#ht_3623wt_966
    http://cgi.ebay.ca/ws/eBayISAPI.dll?...#ht_3021wt_911

  19. #19
    Zoom zoom zoom zoom bonk znomit's Avatar
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    Quote Originally Posted by cyccommute View Post
    If you want a light that creates enough light for riding on trails, you definitely don't want a generator powered light.
    Oh rubbish.
    eg
    http://www.candlepowerforums.com/vb/...d.php?t=226969

  20. #20
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    Quote Originally Posted by cyccommute View Post
    If you want a light that creates enough light for riding on trails, you definitely don't want a generator powered light.
    Not necessarily true. Generators are expensive, and this light (E3 Triple) is expensive too, but it puts out 800 lumens, just as much as the Magicshine, at high speed:
    http://www.peterwhitecycles.com/supernova.asp

  21. #21
    Seņior Member ItsJustMe's Avatar
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    Quote Originally Posted by crazzywolfie View Post
    thanks for the advise and info. now that i know what i'm kind of looking for now i have been searching and found a few in my price range right now and was wondering what you think.
    http://cgi.ebay.ca/ws/eBayISAPI.dll?...#ht_3623wt_966
    http://cgi.ebay.ca/ws/eBayISAPI.dll?...#ht_3021wt_911
    Well, they're full of **** on the specs if nothing else. If the first one is really 17 watts, and it uses 3 AAA cells, which is 4.5 volts, that means it's drawing 17/4.5 = 3.7 amps from the AAA cells.

    First off, AAA cells won't even deliver ONE amp. But even if they did, that would give you about a 10 minute runtime.

    They may be trying to imply that it puts out as much light as a 17 watt incandescent lamp. But they'd need at least a 2 or 3 watt LED to do that, and even that is problematic with AAA cells.

    Same analysis holds for the other one.

    If you do decide to get these, be sure to let us know how it works out. I suspect that you'll go down the road a bunch of us did (including myself) - I spent $20 to $35 each on about 5 lights before finally giving up and spending the money to get a real light. I blew more money on crappy lights in the end than if I'd just bought a good light to start with.

    I think a lot of us have a shoebox full of crappy useless $20 lights that we'd be happy to mail to you.
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  22. #22
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by znomit View Post
    See below.

    Quote Originally Posted by jeisenbe View Post
    Not necessarily true. Generators are expensive, and this light (E3 Triple) is expensive too, but it puts out 800 lumens, just as much as the Magicshine, at high speed:
    http://www.peterwhitecycles.com/supernova.asp
    The operative phase being at high speed. What speed is "high speed"? 5mph, 10mph, 20mph? Might work well for downhill mountain biking but won't work at all for uphill. I can point you to any number of climbs around Colorado that would impossible for even a strong rider to maintain 5mph. And what happens when you stop? If you are in the middle of the woods on a bike that you can only generate light by turning the wheel at 5mph, you could be stumbling around in the dark a whole lot. There are any number of places where it's prudent...even in full daylight...to walk a section. What then?

    Sorry but for riding trails, you want a steady light output that is independent of speed. That cuts dynamo lights out of the equation.
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  23. #23
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    Quote Originally Posted by crazzywolfie View Post
    thanks for the links. those lights look great but there too expensive for me. i might just try cutting up a 6 volt flash light and sticking a 4.5volt bulb in it so that it should work with my generator
    Your bike generator puts out 3 watts nominal at 6 volts and .5 amp. The Halogen light you want to run that your buddy offered is probablty close to 60 watts or 5 amps at 12 volts. No way that you can use the bike dynamo to charge the battery for much run time. For 1 hour of running if using a lead acid battery you want 10 amp hours of capacity as you do not want to run a lead acid nbattery down much below 50% if you want decent life from it. Be heavy as hell. Two hours run time would be a 20 amp hour battery.

    Spend the money on something like the Magicshine lights as they are a practical and lightweight solution. What you are thinking of is neither practical nor will it be that much cheaper by the time you purchase batteries, a charger etc.

    The LED flashlights tend to have beams which are too narrow for mountain biking off road at night. For that you want a relatively wide beam so you can see branches etc.
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  24. #24
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    i understand that i can not use a 12 volt light because the amount of wattage would greatly exceed the output of the generator. my generator is only 6 volt AC 3 watts or 4.5volts DC. i think i might try the 17 watt one. i have lots of rechargeable AAA batteries from my remote control cars and i don't want to spend too much money on a light for my bikes that i get for free.

  25. #25
    Seņior Member ItsJustMe's Avatar
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    Read my post above on the "17 watt" LED you linked to. It's not possible to draw 17 watts from three AAA cells. That's about 4 times the power that a AAA cell can put out at its best. I think what you'll wind up with if you buy that is a not-particularly-impressive cheap flashlight.
    Work: the 8 hours that separates bike rides.

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