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  1. #26
    Senior Member dougmc's Avatar
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    Quote Originally Posted by Burton View Post
    The closest I've come so far is adapting some automotive 12V LED lights to mount on a bicycle and run off 11.1V RC Lipo batteries. About 15 or 16 hours of run time for dual lights on solid with a good combined 500 lumen shaped ouput that doesn't dazzle following traffic but paints the whole road red behind the bike - clearly visible from 2000+ feet
    500 lumens means at least ten watts for that style of LED (efficiency isn't a big concern, as they're already way better than the incandescents that they replaced.) For that to last 15 hours, that means 150 Watt*Hrs, which means about a 12,500 mAh 3s battery. That's a big honking R/C battery -- about two to three pounds.

    Do you really ride with a battery that large? Where do you mount it?

    Personally, I've found lights like these to be pretty good -- have about a meter of them total in various colors around your bike, and nobody will miss you. But at five watts/meter, I generally go for a 2000 mAh 3s battery or so -- it'll power them for about four hours, which is generally enough.

  2. #27
    Transportation Cyclist turbo1889's Avatar
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    Quote Originally Posted by ItsJustMe View Post
    AA is common, but as for me, I'm trying to phase them out of my life. Whenever possible I buy stuff that has built in LiPo batteries. Cylindrical batteries waste space versus flat batteries, the door for removable batteries wastes space and introduces both a place for water to get in and a place for the connection to the battery to fail. LiPo battery controller chips have gotten extremely good, and if the manufacturer uses good quality cells, they should last for a LONG time.
    I too initually thought that built in batteries were ideal until I got a few years experience with them. Then I had my fill of them and went back to using lights with replaceable batteries or an external battery pack where i can replace the whole pack. Built in batteries have the disadvantage of - well - being built in. Once the battery starts to wear out it is difficult or impossible to replace and a perfectly good light except for the battery is rendered electronic waste just due to the battery wearing out and under "real world" use conditions the lifespan is far less then what most would like you to believe. Then there is the fact that you can't carry spares and swap in a fresh set of batteries on long continuous rides at night that exceed the range of a single battery charge which is exactly what happens when you try to combine high light output with minimal weight like on a bike light.

    Quote Originally Posted by dougmc View Post
    I agree with you about the ubiquity of the AA alkaline, but have a minor nit about the voltages.

    Alkalines start at 1.5v and go down from there.
    NiMH and NiCds start at 1.4v and go down from there.

    The NiMH 1.2v figure is a "nominal' figure, below which the battery is nearly dead. The alkaline 1.5v is an initial figure, at which the battery is brand new.

    Basically, it's an apples to oranges comparison, though yes, I do realize that everybody does it for some reason.

    You're exactly right bout AA vs AAA, however. I'd pay a little extra for a tail light that took one AA rather than two AAAs, if for no other reason than AAs cost about the same as AAAs yet hold about 3x the energy.

    I'm also not a fan of lights that take three cells -- two or four cells is better than three cells, because batteries tend to come in packs of four and the cheap rechargeable chargers generally do two or four at a time -- but not three.

    But all of these are bigger issues for headlights rather than taillights, as tail lights tend to not hit the batteries anywhere near as hard.
    Yes, yes, I'm aware of the difference in how the voltages are designated and that it is not an apples to apples comparison. I just used the normal voltage specs. because together they pretty much explain that the light needs to be able to run off of a voltage of between 1.5V and 1.2V to ensure compatibility with both alkaline and NiMH rechargeable cells.

    Even better was a very unique arrangement I have seen on one electronic device (not a bike light) that had a dual use battery compartment that took 2@AA size batteries running in electrical series that mounted in the "+" shaped battery compartment parallel in the vertical or alternately 2@123A cells running in electrical parallel that mounted in the "+" shaped battery compartment parallel in the horizontal. And there was also a USB circuit that would charge the batteries (either rechargeable NiMH AA's cells or rechargeable Li-Po 123A cells) while they were in the battery compartment without having to take them out of the unit and could also be used as an external power input as well.

    That's a pretty slick set-up in my mind and I think it would work nicely for a bicycle tail light. Obviously such an arrangement adds some considerable complexity to the electronics since they must be able to operate on a wider voltage range (about 2.3V to 4.2V) plus having two intelligent charging circuits, one on the AA side that can tell the difference between rechargeable NiMH and non-rechargeable alkaline, and the other on the 123A side that can tell the difference between rechargeable and non-rechargeable Lithium batteries but still a real sweet set-up in my opinion to provide some incredible diversity for power options especially when you consider the option of using the USB port to connect to a large external battery pack for extended run time.





    One additional idea:

    A light that is steady on is good for others on the road to track your position since a steady light gives their eyes something to "lock onto" long enough to judge your position and speed but isn't very good at getting their attention and getting them to notice you.

    A light that continually flashes is good for getting the attention of drivers and making sure they notice you but is very difficult for the eyes to "lock onto" to judge relative position and speed and it is very difficult to judge how far away a flashing light is and if you have only a constant flashing tail-light sometimes drivers will think you are farther away they you are and not realize you are right in front of them until it is almost too late. This is especially true in inclement weather such as a rainy dreary night.


    Currently I use at least two two tail lights a very bright 150 to 200+ Lm constant on tail light paired with a bright flasher of at least 50 Lm if not more but not as bright as the steady light separated from each other by at least a foot of distance or so to get "the best of both worlds" so as to both get people to notice me at night and also give them a constant on light for them to accurately judge my position and speed.

    "The best of both worlds" could also be accomplished with a single bright light with the right flashing sequence. If you set a mode on the light so that it would stay steady on for about 3-seconds of time or so which is long enough for most peoples eyes to lock onto something and judge its relative distance, position, and speed and then have the light give two bright short "Pop !" flashes about 1/6-second duration over about 1-second of time and then have another long steady 3-seconds constant on cycle and repeat that over and over. Basically set-up the same way they do on high end motorcycles brake lights so when the brake light is first engaged it gives two quick hard bright "Pops !" of light to get peoples attention and then goes to a constant on setting.

    That is a kind of flash pattern that so far I have not yet seen in any current bike tail light but I think would be very useful.

  3. #28
    Seņior Member ItsJustMe's Avatar
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    Quote Originally Posted by turbo1889 View Post
    I too initually thought that built in batteries were ideal until I got a few years experience with them. Then I had my fill of them and went back to using lights with replaceable batteries or an external battery pack where i can replace the whole pack. Built in batteries have the disadvantage of - well - being built in. Once the battery starts to wear out it is difficult or impossible to replace
    I've generally found it possible to replace the battery in most anything. There are places selling LiPo cells in almost any size you like.

    In addition, in my experience sealed units with built in batteries last just as long as units with replaceable batteries, which in my experience tend to be much more fragile and much less waterproof.
    Work: the 8 hours that separates bike rides.

  4. #29
    Certified Bike Brat Burton's Avatar
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    Quote Originally Posted by dougmc View Post
    500 lumens means at least ten watts for that style of LED (efficiency isn't a big concern, as they're already way better than the incandescents that they replaced.) For that to last 15 hours, that means 150 Watt*Hrs, which means about a 12,500 mAh 3s battery. That's a big honking R/C battery -- about two to three pounds.

    Do you really ride with a battery that large? Where do you mount it?

    Personally, I've found lights like these to be pretty good -- have about a meter of them total in various colors around your bike, and nobody will miss you. But at five watts/meter, I generally go for a 2000 mAh 3s battery or so -- it'll power them for about four hours, which is generally enough.
    Twin 3W red LED lights that draw less than an amp each tied into a 6,600mAh 3S1P Lipo RC hard case that mounts vertically behind the seat post. Thats only 73.3 Wh. I do have some 5,600mAh packs that are wired to clip together for extra capacity but two of those aren't any bigger than this one. The cell quality specs allow for a smaller lighter build although the packs are more expensive. Two will fit inside a Cage Rocket when I use them to power equally ridiculous front lights. Alternately it'll mount on the top tube, or on top of the stem, or in a small frame bag.

    The problem is that after driving with these now for almost two years - everything else comes up short. Am currently experimenting with shaping the rear light outputs because it'll probably let me use one instead of two rear lights.

    What would be REALLY interesting would be a hub dynamo designed to charge a LARGE capacity battery during the daytime, so that higher powered lights could be driven using battery power after dark. Currently the light output associated with a generator system is directly related to the nominal hub wattage output. It doesn't have to be. The time spent spinning a generator with the lights off could also be made usefull storing watts.
    Last edited by Burton; 03-27-13 at 07:09 PM.

  5. #30
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    Make it look good. There are so many ugly lights on the market right now...

  6. #31
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    I would like to thank everyone for the feedback. We've finished collecting data using various methods.
    Now we are trying to finalize and prioritize our findings.
    If anyone is willing, would you please answer two questions on an online survey? It will only take 1 minute and is completely anonymous.
    http://www.surveymonkey.com/s/C9LTW6T

  7. #32
    Senior Member Road Fan's Avatar
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    Quote Originally Posted by tcasselm View Post
    Hi Everyone,

    I'm a graduate student at MIT taking an entrepreneurship class. I'm working with a local Cambridge start-up and we're working on a new rear bike light.

    I would love to hear what your frustrations are with the current lights on the market and if there are anything you wished a rear bike light would do that it currently doesn't.

    I appreciate any feedback that I can get.

    Regards,
    Thomas
    I really don't have a wish list, and as a practicing engineer I don't have total faith in "voice of the customer." Customers know what bugs them or excites them, but have not engineered the problems that the light must solve. Have you had a course yet in systems engineering or product design? I like the writing of Steve Eppinger and Stuart Pugh (rip). For Pugh I really like the book "Total Design." I'd like to see a lamp that is designed to meet the following design goals:

    1. Distribute adequate light to the positions where the people who need to see me and whom I need to see me are going to be located
    2. Not place significant light in other zones
    3. Don't overpower it - it's a hazard to other drivers to compromise their vision, though some cyclist buyers will say "I just want to be bright, the more the better"
    4. Consider if you can economically match the output requirements of automotive taillights and side visibility lights

    Become the Acoustic Research of bicycle lights, not the "38 Brite LEDs!" selling on Ebay.

  8. #33
    Senior Member Richard Cranium's Avatar
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    Become the Acoustic Research of bicycle lights, not the "38 Brite LEDs!" selling on Ebay.
    How do you know if the guy "likes" AR?

    The OP makes a pretty big mistake in asking for "spit ball" info without requiring specifications or limitations.

    There in no challenge or success for a product without an understanding of the needs and competition of its intended market.

    Good tail lights = already done, been there got the t-shirt....... now - try it again - but sell it at ten dollars.......
    Sorry about my comments - I thought you wanted honest feedback.
    2003 Lemond Wayzata - 2002 LeMond Malliot Jeune

  9. #34
    Senior Member
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    I use the Dinotte 140R, which I love, the one thing that I wish was that I could power that light from my generator hub. There are no bright blinking generator powered tail lights that I am aware of. The ideal would be something like the Dinotte, with a Li Ion battery, which uses the generator to keep the battery charged.

  10. #35
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    Quote Originally Posted by turbo1889 View Post
    One additional idea:

    A light that is steady on is good for others on the road to track your position since a steady light gives their eyes something to "lock onto" long enough to judge your position and speed but isn't very good at getting their attention and getting them to notice you.

    A light that continually flashes is good for getting the attention of drivers and making sure they notice you but is very difficult for the eyes to "lock onto" to judge relative position and speed and it is very difficult to judge how far away a flashing light is and if you have only a constant flashing tail-light sometimes drivers will think you are farther away they you are and not realize you are right in front of them until it is almost too late. This is especially true in inclement weather such as a rainy dreary night.
    The "lock onto" problem is way over-rated.

    It's hard to judge the distance of a steady small light too. The fact that the rear lights are seen from behind also makes determing speed hard even for flashing lights.

    If you are "right in front" of them, the position of a rear light is going to be rather poor anyway. And you should have reflecting gear that allows the headlights be be useful well before being "right in front" of the driver.

  11. #36
    Senior Member trx1's Avatar
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