This article is from the Misc Bicycles FAQs, by various authors.
From: grande@cbnewsd.ATT.COM (brad.l.grande)
> A while back, I solicitided recommendations for upgrading/replacing
> the lighting system I currently have on my commuting bike (union
> halogen battery system (gel cell 6v 4 amp) with .4 amp bulb) to
> something a little bit brighter.
> Well, I thought of another possibilty. How about using a car
> headlight? Sure, they're 12v and ~4.5 amps, but they're cheap and
> easily found (I've seen auxiliary rectangular lights that look to be
> about 4" by 2-1/2" for $40 a pair (Canadian $, mind you) in many
> stores), and they claim a rated lifetime of 500 hours! Best of all,
> replacement bulbs are available for about $5. Maybe I could get one
> with a high beam, as well.
> Of course, the drawback is that I'll need to buy another 6v battery
> and hook it up in series with my present one (another $30), and the
> light will last less than 1 hour (and I'll have to get a 12v
> taillight, too). Currently, I have my battery nestled in a bottle
> cage that is attached (by hoseclamps) to the seat tube and faces
> backwards. It would not be too difficult to attach another bottle
> cage on the front side (the braze-ons are there). I am wondering
> whether there are any batteries currently produced that run 6v (or
> 12v, for that matter) and store > 4 amps, and are still small enough
> to fit in a water bottle cage (or something close to that size -- I
> could custom make a holder). So far, I haven't found anything that
> comes close.
> - Scott
This is what I did, Fish, of Spike bike fame, sold me the other half
of a halogen driving light, about the size you mention and housed to
bolt to a bumper. Fish estimates that the light is about 65 watts. I
picked up a new Gates CYCLON (cute name, huh?) 12V 5AH gel cel at a
hamfest for $15. It is too big to place in a water bottle cage, but I
keep it in a side pouch of my commuting pack and I built a trickle
charger for home and another one for work. I mounted the light and a
utility trailer red tail light on my bike along with a Molex quick
disconnect and a toggle switch. I found that the frame of the bike
provides an adequate ground return path, so I only had to run one
This light is EXTREMELY bright! I have had no close calls at all, in
fact, cars seem to pull over to pass way before they reach me. I feel
safe with this set up. When I was in the planning stage, I was going
to get fancy and put brake lights and blinking turn signals, but
thought that it may be more dangerous to look like a motor cycle than
like a brightly lite bicycle. I figured if I looked like a
motorpickle, cars would expect me to behave like one.
The battery measures 4" x 3" x 5.5" and weighs around 4 lbs. I figure
that I should get about 45 minutes from a charge. I have never needed
it more than for 25 minutes, and there is no noticable change in
Now that I have rambled on, I know of two sources of batteries.
Digi-Key corp is a mail order house. Look in the last few
pages of their catalogue. They carry Panasonic gel cells.
Their number is 1-800-344-4539 You can get from them a 12V
6.5AH cell measuring 6" x 2.5" x 3.75" for $29.25, a 6V 6.5AH
cell - 6" x 1.34" x 3.7" goes for $15.75. They have many
other sizes as well.
The second one, which unfortunately I cannot locate their
address, is called, "Mr. Nicad" E. F. Yost Company. If I
recall, they are located in Madison Wisc. They do mail order
and carry more brands than just Panisonic. I will look again
tonight to see if I can find their address. You could call
information for Madison, or maybe one of the Madison area
rec.bicycles.readers can look it up for you.