Each motorcycle rider is unique, and we express our individuality by customizing our motorcycles. From engine performance upgrades to custom paint jobs, most riders seek the services of professionals for these skilled services. When it comes to adding accessories such as lights, loud horns, heated grips or hookups for electric riding gear and battery chargers, many riders take the do-it-yourself approach. Doing it yourself can save you a lot of money if you have the right tools, skills and knowledge. Adding accessories to your motorcycle’s electrical system, while not difficult, does require special attention to proper wiring technique, circuit design and protection.
Most riders should be concerned about damaging the electrical system of their motorcycle and possibly voiding their warranty. The biggest danger, however, that exists from incorrectly wiring electrical accessories is fire. An inexperienced shade tree mechanic can overlook the need for installing a fuse on every added circuit. Compound this with installing wires in such a way that they rub against the frame as the motorcycle vibrates, and you have a recipe for disaster. When the insulation is rubbed off the wire and the exposed conductor makes contact with the frame, which is usually the common ground, you have short circuit. Without a fuse protecting the circuit, the shorted wiring will heat up and set the remaining insulation on fire. Using a wire that is too small to carry the electrical load of the accessory also can cause the wire to heat up and melt the insulation, thus causing a fire.
Every part of your motorcycle’s electrical system was designed to perform its function safely. A key part of this circuit protection is in the form of circuit breakers and, more commonly, fuses. Each electrical device draws a specific amount of power or load to operate. When adding accessories, it’s important to determine what size of circuit protection and wire to include in the install.
Here’s how. Electrical load is expressed in a unit of measurement called watts. Modern motorcycles use a 12-volt system. Knowing the wattage of your accessory, divide the watts by 12 volts to determine the amps, which will guide you to the right wire and fuse to choose. Fuses are rated in amps, and are designed to blow before the wire could be overheated either by the load or a short circuit. Correct wire size is based on the number of amps the circuit will use. Good circuit design uses a wire capable of carrying the load plus a little extra for a margin of error. For an in-depth look at wire sizing, visit the Engineering Toolbox, which has a useful wire sizing chart. Information about fuses can be found at 12 Volt Planet.
Prepared with this knowledge, you can safely install electrical accessories on your motorcycle—if in doubt, however, there is value in having a professional do the job.
Till next time ride safe!