How to Wire Relays 101

If you have an electrical load that’s quite a ways from your fuse block and you want to control it with a switch from a long distance, you’ll need a relay. In this guide, we’ll walk you through the purpose of relays, how to wire them, and even how to use Bluetooth-controlled relays for a more advanced setup.

How to Wire Relays – VIDEO

What is a Relay and Why Use One?

A relay is an electrically controlled switch that allows a low-power circuit to control a higher-powered one. This is useful when:

• Your load is located far from your switch, reducing the need for heavy-gauge wiring.
• Your switch cannot handle the high current required by the load.
• You want to control a high-powered device, such as off-road lighting or a winch, with a low-powered toggle switch.

Components You’ll Need

Before wiring your relay, ensure you have the following components:

• A Blue Sea Blade Fuse Block (or equivalent, such as the Progressive Dynamics Fuse Block, Blue Sea Safety Hub, or Tiger Expedition UFO 200)
• A relay
• A switch
• Appropriate wiring and connectors
• A Victron Lynx Distributor (or another power distribution hub for your system)

Wiring a Relay: Step-by-Step Guide

1. Powering the Relay:
   • The relay receives power from the fuse block.
   • A switch is connected to the relay to control it.
2. Understanding Relay Functionality:
   • A relay acts as an intermediary between a switch and a load.
   • When the switch is turned on, the relay closes the circuit, allowing power to flow to the load.
3. Wiring Diagram Breakdown:
   • Circuit 1: The switch sends a low-power signal to the relay.
   • Circuit 2: The relay then closes, allowing power to flow to the load.
   • All negative connections are tied together.
4. Voltage Drop Considerations:
   • Running long wires directly from a switch to a load can cause voltage drop and require thicker, more expensive wire.
   • Using a relay allows you to run smaller gauge wire for the switch while keeping high-power wires short.

Using a Bluetooth Relay for Wireless Control

If you want to eliminate physical wiring for the switch, a Bluetooth relay is a great alternative. Instead of running wires from a switch to the relay, you can control the circuit wirelessly.

Best Bluetooth Relay Option: Victron Smart Battery Protect

The Victron Smart Battery Protect is a trusted option. It functions similarly to a relay but can be controlled via the Victron Connect app.

Wiring a Bluetooth Relay:

1. Connect power from the fuse block to the Smart Battery Protect.
2. Run the negative connection to complete the circuit.
3. Use the Victron Connect app to toggle the circuit on and off wirelessly.

Advantages of a Bluetooth Relay:

• No need for a physical switch.
• No additional wiring required.
• Can handle up to 220 amps, making it suitable for high-power applications.
• Ideal for light loads, such as water pumps or lighting.

For those looking for a more comprehensive, centralized control system, the REDARC TVMS system provides additional functionality, including touch-screen and app-based control. We’ll cover that in an upcoming post!

Final Thoughts

Now that you understand how to wire a relay—both traditional and Bluetooth versions—you can implement this in your off-grid electrical system. Whether you’re managing lighting, high-power accessories, or just looking for a cleaner, more efficient way to control circuits, relays are an essential tool.