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8.16 Custom Lighting Systems


This article is from the Misc Bicycles FAQs, by various authors.

8.16 Custom Lighting Systems

From: koren@fc.hp.com (Steve Koren)

Here is an updated version of a response I posted to someone's query
about custom lighting systems about a year ago. There seems to be
enough interest now to warrant posting it again. Even if you don't
build such a system, the address for the battery company (ADC) might be

> Does anyone have experience/suggestions for someone (me) looking
> for a good lighting system.

If you don't mind hacking together a system from parts, I have a
setup I can recommend. It consists of the following parts:

* A Sylvania plastic car headlamp. Very light weight. The model
number is HP4656, and it is a halogen lamp in a rectangular
configuration. I got mine at Checker Auto Parts. 35 watts. Price:
$12 to $16. Be careful to get the HP model and not the H model,
which is similar but made of heavy glass instead of lightweight
plastic. Alternatively, you might be able to find tractor lights in
various capacities.

* A 6 watt red car or truck marker light. I payed $2.50 for this at
K-mart. Its much brighter than most bike taillights, especially if
you tape a bit of aluminum foil behind each bulb to reflect more
light. Its about 4" wide, 2" tall, and 1" deep, in a rectangular
plastic case with rounded sides, and very light weight. It also has
a wide beam dispersion angle, which means it can be seen by someone
off to the side, unlike many commercial bike taillights. Price:
$2.50. It looks somewhat like this from the front. Inside there
are bulbs where the "BBB"s are.

           /                \
          |  BBB       BBB   |
           \                /

* A 12 gel cell battery. The following company has batteries ranging
from 1 to 20 AH. The minimum practical capacity for running this
head/taillight combination is probably about 5 AH. After 12AH the
battery gets very heavy, so the reasonable range of batter sizes is
around 5 to 12AH.

You can get gel cell batteries, as well as other interesting
electric gizmos, from:

American Design Components
1-800-776-3700 or 1-201-941-5000
815 Fairview Ave
PO Box 520
Fairview, NJ 07022

Price: $18 for 7AH @ 12V. You can trade off weight for running time
by getting smaller or larger batteries. The headlight draws about
3A, and the taillight about 0.5A. That will let you determine the
battery size given your desired running time. Note that batteries
loose some capacity when discharged quickly or in the cold. Also,
lead acid batteries don't like to be discharged all the way - you'll
extend their life by only discharging them 1/2 way. Plan on some
excess capacity beyond what you think you need for these reasons.
You can also buy two 6V batteries and connect them in series if you
want, but just getting 12V is a bit more convenient. To find out
the AH capacity you need, given your desired running time of X
hours, use this rough indication:

         capacity = X * 3.5 * 1.5
                    ^    ^     ^---- derating capacity for cold, safety
                    |    \--- Current draw of headlight + taillight
                    \-- Your desired running time in hours

For example, to insure about 1.5 hours of running time per charge,
you'd need about 7 to 8 AH.

* Some reasonably heavy guage wire from Radio Shack, along with push on
connectors, a switch, and whatever else you want. Price: $10 worth of
stuff, about. Get sturdy enough wire - this will have 3 to 4 amps
passing through it. 14 guage should do. Plastic strap-down things
are useful to secure the wire to the frame. The push on connectors
are the plastic covered ones that look like this from the end:

       (___)    ---

The slotted one slides into the other half, and there is plastic
insulation over the whole thing.

* Transformer to use as battery charger (if you don't already have
one). Cost: $10. Available mail order, or from Radio Shack. The
transformer should put out 14V@1A in order to charge the battery.
12V won't work, although some transformers rated at 12V put out a
bit more even under load.

* A container for the battery. For my 7AH battery, I have a "Case
Logic" CD case that fits it well, and which I strap to the rear rack
of my bike. For my 10AH battery, I use a Nashbar "Rack Packer".
This works well for the battery and taillight. Whatever you use
should be waterproof. Your local Target, K-Mart, etc, should have
something useful. Check CD and cassette cases - they tend to be of
about the right size. Cost: $4.00 for the Case Logic CD case.

* Some black electrical tape, double-sided sticky tape, short sections
of velcro, some of those plastic tie down things, and a few machine
screws and matching nuts. Cost: $5 - $8 for all.

* The mounting bracket from a Cateye headlamp. Cost: $11 to $15
including the light which you can use as a backup.

* A piece of scrap 1/8" thick aluminum sheeting.

That's all for the parts list, although you might find a few other
things you need depending on how you put your specific system together.

I've been running a system like that for about 4 months now, and I love
it. Using both an auto taillight and headlight gives you great visibility
in traffic. The headlight is also great for lighting up dark roads and
trails. Do something like this to construct the system:

1. If you have bought two 6V batteries instead of a 12, you'll need to
connect them in series. If so, tape the batteries together along
their long dimension with some strong strapping tape (the stuff
with fibers running the length of it), like this:

        [ +   - ]
        [ -   + ]

So with a short piece of wire, join the + of one and the - of the
other, like this (where | represents wire):

        [ +|   - ]
        [ -|   + ]

If you have a 12V battery, skip this step.

2. Soldier short 8" sections of wire to the battery terminals, one to
+ and one to -. Use black and red so you can tell them apart
later when you can't see the terminals any more.

3. Soldier the push-on connectors to the ends of the wires from #2.
Color coding these is also useful.

4. Put this battery assembly in your rack pack or case. I hold my
case to the rack with either rubber tie-downs or a nylon strap
available from Target or K-mart for about $1.50. If your case is a
bit bigger than your battery, stuff something else like a spare
tube or a bit of foam padding in there to keep the battery from
moving around.

5. Temporarily put one end of a red wire in the pack, and run it from
the pack, along the top tube, and up to the handlebars. Don't
fasten it down, this is just to measure out the length. Leave
yourself a foot or so of slack and cut it off. Then cut the other
(black) wire to the same length.

6. This wire will form your power bus. It starts at the battery and
powers both the front and rear lamps. This means you have to make a
split at the back of each, like this:

                                        /------ (to battery)
     (to headlight) --------------------
                                        \------ (to rear light)

That's easy to do. Get two short pieces of wire and soldier them
to the end of the long one to form the branch. Wrap this well with
electrical tape or heat shrink tubing when you're done. Make both
wires look like this.

7. Soldier push-on connectors to each of the ends of the forked wire
you made in #6. Make sure the gender of the connector matches the
connector you put on the battery wires up in #3.

8. Tape velcro to the tail light along the bottom edge. Tape the
matching piece of velcro to your rear rack, or sew it to your rack
bag. There are several other ways to mount the taillight also - I
recently changed mine to use an aluminum bracket I made for this

9. Open the taillight (it unsnaps) and solier a short piece of wire to
the + and - terminals. Be careful not to melt the plastic case.
There are holes in the back of the case to poke the wire through.
Soldier push-on connectors to the wires, and snap the case back

10. Fasten the taillight to the rack or rack pack with the velcro.

11. Connect one fork of the + cable to the battery with the push-on
connectors. Connect the other to the taillight. Do the same with
the other cable. The long part of the cable should be dangling,
and will be run to the headlight.

12. Tie a knot in the cable around the bar of your rear rack. This will
keep it firmly in place.

13. Along the length of the cables, tape them together with the
electrical tape. Don't twist them, just wrap the electrical tape
around them every 8" or so to keep them together.

14. Run the cable pair along the under side of your top tube and fasten
it securely every 8" with the plastic tie downs. With proper
placing, you can make sure it doesn't interfere with a frame fit

15. Trim the cable such that it ends at your handlebars with 4
inches of slack. Soldier push-on connectors to the ends.

16. Look at the Sylvania headlamp. It has 3 terminals. In various
combinations, these can make a 10 watt, 35 watt, or 70 watt light.
(There are two filaments in the lamp which can be run singly or in
pair, and in addition, at half intensity). Apply voltage to these to
find which two terminals make the 35 watt light. Soldier short 4"
pieces of wire to them, and put push-on connectors on the ends.

17. Mount the light to the handlebars. This is the hardest part. I
used a mounting bracket from a Cateye headlamp. This mount can be
unscrewed from the Cateye and has two halves: one connects to your
handlebars, and the other has a hole and can be screwed to a piece
of aluminum plating 1/8" thick. The setup, viewed from the side,
looks like this, where "O" is the handlebars viewed in cross
section, "<" is the headlamp, and "_" is the aluminum sheeting
screwed to the Cateye mount:


Make the aluminum wide enough at the front so that it is almost as
wide as the headlamp, and use the double-sided tape to attach it
firmly. (Clean both surfaces well first). From the top, the setup
looks like this, where "||" are the handlebars, "<" is the light,
and "-" is the aluminum bracket.


You will have to be able to cut the aluminum sheet to size, and to
drill a hole in it for screwing it to the bracket, so you need a
few tools for this. If you don't have them already, you can
probably borrow them. I've found that velcro does NOT work well to
attach the light to the aluminum, because the light will tend to
rock when you go over bumps. Heavy duty double sided tape is

18. Congrats, you're done. Charge up the batteries, and connect the
front push-on connectors to light the lamp. (You can optionally
configure in a switch if you don't like having to mess with the
push-ons every time - I put a switch in a small plastic box from
Radio Shack and use this to turn the system on and off). The light
should be as bright as an automobile headlamp (because it actually
is an automobile headlamp).

I think this system stacks up pretty well to the original poster's

> My chief concerns are:

> - Throwing light, and lots of it.

Yup. Hard to beat the 35 watt headlight/6 watt tailight combo. If you
need more (doubtful!), the sylvania headlight also supports a 70 watt
mode using two filaments at once. I've never needed this. The 35 watts
either beats or matches any available commercial bike light.

> - Do this for around two hours between charges.

You can get around 2.5 hours out of it using a 10AH battery. You can
buy a 5AH or 6AH battery if you don't need that much time.

> - Robust enough to withstand commuting.

I've used it nearly every day for 3 winters with no problems. Just be
sure to fasten the stuff on the bike securely.

> - I do not want to spend over $100. (Is this realistic?)

Total cost should be around $60 to $85 for the stuff I listed above,
plus some time to connect it all up. I consider 10 watts to be the bare
minimum for a headlight, but its hard to find even a 10 watt system
commercially for under $100. This is 35 watts for ~ $70.

> - Not involving a car battery, or weight equivalent.

This is the weakest part here. The 10AH@12V batteries weigh 6 to 7 lbs,
(which is *lots* lighter than a car battery, but still heavy). You
could replace the 10AH batteries with 6 or 8 AH versions for lighter
weight at the expense of running time. ("Running time, weight,
brightness: pick any two").

> - Either easily removeable, (to prevent theft), or

Its pretty easy to remove. I can take off the headlight in 10 seconds,
and remove the battery in another 30, although I rarely do so.

Hope this gives you some ideas. The chief drawbacks to this system are:
1) the weight, and 2) you need some modest soldiering and mechanical
ability to hook the stuff up how you want it. However, it puts out lots
of light, it can be customized to suit your needs (for example, I've
added a 15V voltage gauge from Radio Shack to give me an indication of
the battery's charge state) and its cheaper than any 35/6 watt
commercial system.


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