There are two ways to wire headlights directly to a battery: using a relay or creating a parallel connection. However, connecting the headlights directly to the battery can drain it more quickly and potentially lead to overheating and fire hazards. To avoid these issues, it’s recommended to either use a relay or wire the batteries in parallel.

Is it possible to directly wire car headlights to a battery?

Wiring car headlights directly to the battery is certainly feasible, and there are three main approaches to doing so. The first involves directly connecting the headlight to the battery. Another option is to use a battery relay, and the third is to create a parallel wiring configuration.

Each of these methods has its own unique set of steps, benefits, and drawbacks. Additionally, these methods are applicable to both cars and motorcycles with some variations. In this article, we will provide a detailed, step-by-step guide for all three methods. First, we’ll start with the initial method.

Direct wiring of car headlights to the battery: a step-by-step guide

Before attempting to directly wire your car headlights to the battery, you’ll need a few tools. Take a look at the checklist below to ensure you have everything necessary:

Required Tools:

  • Scissors
  • Electrical tape
  • Wire and knife
  • Philips head screwdriver

Precautionary and Safety Tips:

  • Wear protective rubber gloves to avoid electric shocks from the car battery
  • Wear safety goggles to protect your eyes
  • Avoid direct contact with battery fluids
  • Check for any visible cracks or damage on the battery
  • Exercise extra caution when handling the positive and negative wires
  • Avoid all potential ignition sources, such as cigarettes or flames.

Step 1: Position the Battery
Before starting, position the battery in a convenient location where you can easily access the wires. Ensure that the battery is placed in a well-ventilated area to prevent overheating issues.

Step 2: Disconnect the Battery
Ensure that the battery is completely disconnected before starting the wiring process. Failure to do so could result in injury as the battery could catch fire.

Step 3: Prepare the Battery for Wiring
After disconnecting the cables, prepare the battery for wiring. Make sure that the battery terminals are clean and rust-free. If there is any corrosion or rust, use sandpaper or a brush to clean the terminals.

Step 4: Disassemble Headlight Parts
Using a Philips head screwdriver, remove the headlight assemblies and disconnect all wires connected to the headlights. Check the manufacturer’s instruction manual for the specific disassembly procedure for your car model.

Step 5: Split and Splice the Wires
You’ll see two pieces of wire. Use a wire cutter to split the top part of the wires, resulting in two wires: an electrical wire and a wire that connects the headlight. Carefully splice the wires together using a wire splicer for convenience.

Step 6: Connect the Wires
Connect the wires to the battery terminals. Attach the negative (-) or black cable to the negative terminal of the battery, and the positive (+) or red cable to the positive terminal of the battery.

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Finally, turn on the headlights to ensure they are working correctly. Congratulations, you’re done!

Advantages and disadvantages of wiring headlights directly to the battery

Pros Cons
More power to the headlight.Brighter and stable lights.Permanent installation May overheat the lights.Voltage surge may damage the lights.High battery consumption.Drains the battery faster.

As with any process, there are both advantages and disadvantages to wiring headlights directly to the battery. One of the main disadvantages is that it can drain the battery faster, as the headlights will continue to run even when the car is turned off.

Guide to wiring headlights directly to battery using a relay

One alternative method of wiring headlights directly to the battery is by using a relay. You may be wondering what a relay does and whether it’s necessary.

A relay is an electronic device that separates power circuits from control circuits, ensuring that the headlight receives adequate power without the risk of overheating or sudden damage from high power surges. Additionally, relays automate the power supply directly from the battery and are cost-effective and easy to set up.

Before diving into the wiring process, it’s important to understand the relay’s terminator pins and their functions. Below is a table outlining the relay terminator pins for quick reference.

Terminator Pin/Number Connection
85 Coil
86 Coil
87 NO (Normally Open)
87a NC (Normally Closed)
30 For both NO and NC terminals

Let’s dive into the wiring process for headlights using a relay. Before starting, make sure to follow steps 1 to 5 as previously mentioned.

  1. Begin by positioning the relay in a suitable place, away from any moving parts.
  2. Take the negative or black wire and connect it to the negative terminal of the relay. If you cannot locate the negative terminal, look for “86” labeled on the terminal.
  3. As mentioned in the table earlier, terminal 86 is a coil that completes the circuit and flows the current from the battery to the headlights. Once connected, use electrical tape to cover the relay terminal.
  4. Next, connect the positive or red wire from the headlights to the positive terminal of the relay. Look for “30” labeled on the terminal if you can’t locate the positive terminal.
  5. Now, take the positive or red wire and connect it to the battery’s positive terminal. If you can’t locate the positive terminal on the battery, look for a “+” sign on the terminal.
  6. Finally, turn on the headlights to ensure that they are properly working.

Congratulations, you have successfully wired your car’s headlights using a relay!

Advantages and disadvantages of using a relay

Pros Cons
Provide the shortest route from the battery to headlights.Prevents voltage drop and surge.Ensure the proper use of the fuse.Can tolerate power loads up to 30 amps. Requires proper setup.May require a good AWG gauge  wire for peak performance.

How to wire headlights directly to the battery in parallel?

Nowadays, most modern vehicles come with default parallel wiring, which has proven advantages over series wiring used in older model cars. If you own an old car and want to switch to parallel wiring for your headlights, follow these step-by-step instructions:

  1. Identify the headlight terminals. The positive terminal is red and the negative is black with a minus (-) sign on it.
  2. Connect one wire to the positive terminal of one headlight and then to the positive terminal of the other headlight.
  3. Connect another wire to the negative terminal of each headlight and then connect them together. By connecting all the positives and negatives, you create a circuit that maintains the same voltage, even if one headlight fails, and that’s the main benefit of parallel wiring.
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However, let’s also consider the pros and cons of using parallel wiring.

Pros and cons of parallel wiring

Pros Cons
Parallel wiring maintains a consistent voltage supply and can help prolong battery runtime. In addition, if one device fails within the circuit, there will be no interruption to the others. Parallel wiring requires more wires as compared to series wiring. It can be complex to adjust the current flow or voltage to meet specific needs. Additionally, increasing the voltage can lead to a rise in resistance within the circuit.

The advantages of parallel wiring in the automotive industry make it clear why it is preferred over series wiring. Therefore, opting to wire your car headlights in parallel is a reliable solution.

Our recommendation would be to use the relay method as it is the safest and most effective way to wire headlights directly to the battery. The relay method ensures the protection of your headlights by controlling the current flow and preventing voltage surges or drops.

When it comes to wiring bike headlights directly to the battery, it is a relatively easy process. First, disassemble the headlight panel using a screwdriver, following the manufacturer’s instructions. Look for a full yellow wire and another bunch of black wires, with one empty slot. Disconnect the yellow wire from the connector and plug it into the empty slot of the black wires. Insulate the other part of the yellow wire with electrical tape. To return to the previous mode, simply attach the yellow wire back to the previous connector.


How many LED lights can a single car battery connect to?

You can connect a maximum of 3 LED lights to a 12-volt car battery. LED lights consume 3.5 volts per light, so 12 volts divided by 3.5 volts equals 3.4. You can wire the LED lights in either series or parallel, but parallel wiring is recommended.

Why do headlights have three wires?

Headlights with three wires are multifunctional, meaning they can be used as both blinker and brake lights. The red wire is the positive cable, the black wire is the second positive, and the white wire is for grounding.

Do headlights need a relay?

Headlights only need a relay if they are high-powered. The relay protects the fuse from damage by high current flow and ensures proper current flow while preventing voltage drops within the circuit.


Wiring headlights directly to the battery can be done safely using either parallel wiring or the relay method. For high-powered headlights, the relay method is the safest option. We hope this article provided helpful solutions for your wiring needs. Let us know if we missed anything so we can cover it in future articles.