How to Run LED Lights From a 12v Battery

LED lights are a popular way of saving money in the home. They last for many hours, and a gently used light can last up to 25 years. Most LED lights are arranged so that they can run off of a 12v battery—in fact, 12v lights can cause a short when plugged directly into a socket, which usually have 110v current. This can be very dangerous, and so the best solution is to run these lights through a relay instead.

Step 1 - Decide Where to Put It

The first thing that needs to be done when connecting LEDs to a battery is to consider where they will go. Batteries operating lights on a high wall, for example, will need to have something supporting their weight. Unless you are installing these near an existing 12v battery supply, prepare to build a ledge, box, or other support. Leaving a battery to dangle will eventually cause connections to break.

Locate a nearby place to put the battery and on/off switch; then, measure the distance between where the lights are and where these will be. This is the length of wire necessary to connect the LEDs to the power supply.

Batteries and switches should be checked for faults before being wired to the LED home lighting system. This can be done by checking the current with a voltmeter, or by wiring both items to a lamp or device which is known to work.

Step 2 - Wire the LED to the Battery

Once the LEDs are in position, examine them and find the leads; the negative lead (or cathode), can be identified in one, or more than one, of these ways: it is the shorter lead, it is a flattened section on a round LED, or inside the LED, each lead is attached to a triangle-shaped node; the positive lead (or anode) is attached to a larger node.

A diode test function meter will light up the LED when correctly applied. When it is lit, the black test lead will be attached to the cathode, and the red test lead will be attached to the anode.

When you are sure which lead goes to which, it is time to solder the wires to the 12v battery. The cathode goes into the ground—it can be soldered directly to the negative port of the 12v battery. The anode should be wired into the on/off switch, which is then wired into the positive port of the battery.

At this point, it is a good idea to check that the home lighting system works. Problems may include a blown fuse or damaged LED (easily done during wiring), or a loose connection somewhere between the lights and the battery. Correcting these problems is a simple task, and if the home lighting system is wired correctly, there should be no problems in using it for the foreseeable future.

Run LED Lights From a 12v Battery FAQ

Why don't LED bulbs work in my car?

Multiple things can go wrong that will prevent LED bulbs from working properly in the car. The power supply could be bad, a connection could be loose, the circuit design might be faulty, or something could have been damaged due to pests or water.

What happens to LED when it is directly connected with battery?

The 12V current of a car battery is very strong. Standard LED lights are not made to handle as much power as what a car battery puts out.

If you connect LED lights directly to a car battery, you are likely to burn out your lights and render them completely useless. You need to mitigate the power flowing to the lights so that they don't receive more current than they can handle.

Can I legally put LED bulbs in my headlights?

In the U.S., headlights are actually regulated at the federal level by the Department of Transportation. This cabinet department ensures that all headlights in all vehicles have relatively the same brightness.

LED bulbs can be swapped out with the halogen bulbs in car headlights. However, it is not legal for you to do this on street vehicles.

You can swap out your bulbs in off-road vehicles that you will not be driving on streets around traffic but you will be breaking the law if you put LED lights in the headlights of a car that you plan to drive on any type of street, be it a city highway or country road.

Do I need a resistor for LED?

A current-limiting resistor should always be used with LED lights. This will prevent differences in voltage from affecting the lights by mitigating the electrical current flowing into the lights.

What size wire do I need for 12V LED lights?

If you want your LED lights to fit into most terminals and holders, use an 18-gauge wire. This is the largest wire you want to use with LED lights.