Install an Automatic Anchor Light

  • 1-3 hours
  • Intermediate
  • 50-125

Anchor lights help other mariners see your boat after dark, but they also serve other purposes, such as giving your boat the “lived on” look while you are away and acting as a general utility light. Most importantly, however, they are the law. Installing your own anchor light is a very simple and inexpensive way (about $15) to provide added security and compliance to your boat. To complete this job you will need basic knowledge of electrical circuits

What’s Needed:

  • 12-volt SPDT relay
  • Fuse
  • Terminal block
  • Wire
  • Soldering gun and some solder

Step 1 - The Law

According to the Inland Rules, any vessel less than 50 meters at anchor needs to have a 360-degree light. This needs to have visibility of at least 2 miles. Anything less than 7 meters needs to have lights anytime it's anchored in a fairway, anchorage, narrow channel or anyplace where other boats may travel.

Step 2 - Making Sure You Are Compliant

When installing your anchor light, make sure to follow the manufacturer’s instructions to ensure compliance with U.S. Coast Guard regulations.

Step 3 - Construction and Materials

Most modern boats utilize solar panels to keep the batteries charged. Your anchor light will be created by using an existing solar panel and an electrical relay. This information is for vessels that have an existing solar panel system.

Step 4 - Basic Components and Assembly

A 12-volt SPDT relay is your main component in this project. You will need to purchase one in which the contacts are rated at 5 amps or higher. This item can be easily found at most electronics and home improvement stores (i.e. Radio Shack, Lowe’s). Most of these small relays fit easily on the underside of the solar panel.

You may also want to consider using a small terminal block.

Have some solder handy as you will need to solder some of the leads on the relay. A quick internet search should yield you a proper diagram.

Step 5 - Day and Night Power

For the light to turn ON at dusk and OFF at dawn (night power), connect a light between the relay’s NC terminal and the negative terminal C (also called the common terminal).

For the power to turn OFF at dusk and ON at dawn, use the relay’s NO terminal and the negative terminal. If needed, you can add separate ON and OFF switches to trigger bigger relays.

Step 6 - Considerations

Again, make sure you follow directions and connect everything as the manufacturer specifies. Make sure you go back and give your work a once over to make sure everything is firmly in place and your solder joints are secure.

Step 7 - Safety First

Install a fuse holder and the correct size fuse. Accidental shorting of the leads between the solar panel and the battery carry the full discharge current of the battery and presents a fire hazard.