Do I Need To Wire A Relay For An LED Light Bar?

A question that I have heard a lot is “Do I need a relay for my LED light bar?”. Apparently, since I own one, everyone thinks i’m an expert. I may not be an expert, but I do have some knowledge when it comes to wiring a relay for these light bars. Before you do it, it’s best to know if it’s truly necessary and how much of a pain in the neck it’s going to be for you. Let’s take a look at some of the information I managed to dig up on top of my personal knowledge.

What Exactly Is A Relay?

If you are new to the light bar world, you may not know what the relay is and what it does. The relay is a switch that allows a low current circuit switch to control the flow of electricity from a high-current circuit. The high-current circuit in this case would be your light bar. Relays are usually used when having a direct electrical connection between the light bar and control circuit isn’t possible.

How Does The Relay Work?

The simple answer here is that when an electromagnetic field is set up, the current is allowed to flow through the coil. The iron armature is attracted by this field and the other end of it pushes the contacts together, which then completes the circuit. When it is switched off, the contacts then open and switch the circuit off.

In the case of the light bar, the circuit that powers the coil is separated completely from the circuit switched on by the relay. This is why relays are used where a low-voltage safe circuit controls the high-circuit of the lights.

After you create a loop of electricity from your battery to your light bar, you put the switch between the battery and the light in order for it to handle the full current of the light. Some switches alone can handle a small amp draw, but if you are using a huge bar such as a 50” that has a high amp draw, it’s going to be too much for the switch alone to handle.

If your switch alone cannot handle a large amp draw, you could end up with overheated switches, melted wires, and reduced current to your lights, which will make them much more dim than you want. If the current of your light bar is above 30W, it is highly recommended that a relay is used.

Can I Use It Without A Relay?

Sure, If you don’t want to take the time to install the relay or think it’s unnecessary, there are a few situations in which you don’t need to do it. If the draw of your light bar is small, you could get away with a toggle switch. Although you can do this, you need to ensure that the switch is rated for more than the draw. You can always look at some charts online to check out whether or not you need a relay.

To determine the current you need to carry, follow these simple formulas:

Computing Voltages and Powers

  • Volts = Watts/Amps
  • Watts = Amps x Volts

Computing Current

  • Current in Amps = The square root of Watts/Ohms
  • Current in Amps = Volts/Resistance (Ohms)
  • Current in Amps = Watt/Volts

Relay Installation Hints And Tips

If you decide that you do need the relay, installing it is going to take a little bit of time and research. Although not complicated, it’s still time consuming and you need to make sure you do it right. You shouldn’t use scotch-locks or butt connectors or anything else that is used as a “hack” commonly by people in the audio industry. There is a reason why you won’t find these in your relay kits.

How to install a Relay on Led Light

The reason that these types of connectors and “easy way outs” aren’t used is because they are prone to failure. If they fail, it could lead to an electrical fire, ruining your wires and possibly your vehicle. The easiest thing to do is use the relay that comes with your light if needed.

One more thing I would like to add is to keep your wire lengths as short as you can. You want to maneuver the wires along the firewalls of the vehicle chassis and away from the high heat areas. If you are placing the bar on your roof, run the power wires through the windshield frame channel. You also want to avoid splicing the wires whenever possible.

Long Story Short

To make this quick and simple, if a wiring harness came with your bar and it does include the relay, please use it. If you don’t have a wiring harness and your light bar draws more than 5 amps, use a relay. If you are switching the bar directly, use a switch with a 10A minimum rating.

I hope that you found this article helpful and it aids you with your relay installation. As I said before, you need to make sure that your switch can handle the power without a relay if you don’t want to install one. If it can’t, use the relay and save your investment.

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