Introduction: Simple, Bright, CHEAP Bicycle Lighting System

As a bicycle commuter, I sometimes find myself riding in the dark.  Even in a city, many streets are so poorly lit that cracks, potholes, unpainted speed bumps, and debris are serious hazards at night.  LED lights are useful for alerting others of my presence, but they are much too dim to help me see.  Serious bike headlights cost hundreds of dollars.  I am not willing to spend so much, especially on something that can be broken or stolen.  Fortunately, an effective lighting system can be made for under $100.

This instructable covers a very simple lighting system based on information from by Steven M. Scharf.  For simplicity, many details are left out of this instructable.  For such details, including charts for selecting lights and batteries, more complicated circuitry, and product recommendations, see

The total cost of the particular system shown here, including Altoids gum, window wipes, and battery charger, is about $60.  The battery charger can be used for other things, and some of the materials will have leftovers for other projects.  This means that two complete lighting systems like the one shown here can be made for under $100.

WARNING: This project involves electricity and heat.  Do be careful now.

Step 1: Tools Used

The following tools will be used to make the lighting system:

- drill
- heat gun
- soldering iron
- wire clipper with jacket stripper
- screwdrivers

Step 2: Determine Your Needs

First you must determine your needs.  The choices made in this step will affect everything that follows, namely

- weight, depending on the size and type of battery used
- brightness, depending on the type and quantity of lights used
- circuit complexity, depending on the quantity of lights and switches used
- cost, depending mostly on the battery

For this project, I merely want one constant headlight bright enough to illuminate the road when traveling below 15mph.  No high beam is required.  No taillight is required.  (I find that AAA-powered LED taillights work fine.)

For this limited purpose, one 12V 20W bulb will suffice.  To power this system, I will use a 2.3AH sealed lead acid battery.  One pushbutton switch will control the light.

For more information about how to determine what lights and batteries to use, see

At the very least, any lighting system will include a battery, a fuse, a switch, and a light.

Step 3: Parts Used

The following parts will be used for this project:

- auxiliary auto light kit (aka racing lights)
- MR16 lamp, with a 12V 20W spot bulb (ANSI code ESX),

- pushbutton switch
- Altoids gum tin
- Velcro stickers

- 2.3AH sealed lead acid battery
- bottle cage
- drain hose connector (rubber with metal hose clamps)
- empty window wipe container

- wire connectors
- heat shrink tubing
- 10A blade fuse
- blade fuse holder
- wire loom

Step 4: Install the Lamp Into the Housing

The lamps that come with auto kits have bulbs rated at 35W or higher.  If you feel like carrying a car battery around and having a headlight hot enough to cook a snack, you can keep the original lamp.  For this project, however, I will use a mere 20W lamp.  Thus, I am removing the auto lamp and inserting a 20W lamp.

Step 5: Prepare the Switch Box

Simply install your switch(es) in your switch box and make sure that the switch box is prepared for all the wires that will run through it.

I am using an Altoids gum tin.  For the pushbutton switch, I drill a large hole in the lid.  For the wires to the battery, I drill two small holes at one end.  For the wires to the light, I drill two holes in the other end.

Technically, the negative (blue in the picture) wire does not need to enter the switchbox, but it helps to keep things tidy.

Step 6: Wiring

For a good fit, you should decide within a few inches where the main components of the system will be mounted.  Then size your wiring based on the paths between the components, remembering to leave some slack, especially when wires reach from the frame to the handlebars or fork.  It would be a bummer to rip loose some wires when making a sharp turn.

You can rely on multiple connectors to be extra flexible.  I do this for a system that I move between bicycles of different geometries.

The majority of time and effort is spent on soldering.  I strip about 1" from each wire and butt solder them together.  Don't forget to thread a piece of shrink tubing onto one of the wires before soldering.  After soldering, slide the shrink tubing over the joint and use a heat gun to shrink it.  If you really mess up, you can fall back on electrical tape.

Attach the fuse holder to the positive terminal.  Attach connectors where convenient.

Step 7: Mount the Components

This step can be the most frustrating.  The bike I am working on has a step-through frame, so is not very receptive to the components.  Therefore, I have to make mountings.

To hold the battery, I attach a bottle cage to the down tube.  Some find the aesthetics of hose clamps to be repugnant; I don't really mind.  I then put the battery inside a window wipe container.  Bubble wrap should prevent the battery from rattling around.  The container fits quite snugly in the bottle cage, so it won't fall out.  The position of the battery is just barely out of the way of both the front wheel and the rider's right foot.

To mount the switchbox, I use some Velcro stickers at the top of the down tube.

To mount the light, I wrap a metal strap (designed for mounting a bottle cage or something) around the left fork tube.  Some lights have much better mountings that this one (but few are as cheap).

The picture of the blue Raleigh shows another lighting system I made.  That system has two lights (high and low beams), requiring two switches and a 7Ah SLA battery (which weighs 6lbs).

Step 8: Charge the Battery

Try to keep the battery fully charged.  The lifespan and effectiveness of most rechargeable batteries is reduced when they are left sitting without a full charge.  Also, some batteries, including SLAs, will "leak", gradually losing a little bit of charge each day.  I charge my battery when I arrive at home.

When attaching a charger, be sure not to reverse polarity.  Attaching a charger backwards may completely destroy your battery very quickly.  Also, I recommend a "smart" charger to avoid overcharging your battery.  Overcharging can destroy your battery and even injure you.

Step 9: Wait for Night and Ride

As you can see from the pictures, this 20W lamp is definitely bright enough to illuminate imperfections in the road surface.  This means the difference between crashing into a pothole and dodging it.

Definitely test ride your bike before you need the light for a long trip.  You will probably find that you need to adjust the angle of the lamp.  Also, you may wish to reroute some wires for convenience or safety.

Lastly, like Jack Burton, never drive faster than you can see!