how to jump starter relay

3 min read 06-02-2025

A dead car battery is a frustrating experience, but a jump starter relay can be a lifesaver. This device uses a relay to protect your vehicle's electronics during the jump starting process, making it safer and more efficient than traditional methods. This guide provides a step-by-step process of how to use a jump starter relay effectively and safely.

Understanding Jump Starter Relays

Unlike directly connecting jumper cables, a jump starter relay uses an additional relay to manage the high current flow during the jump starting process. This protects the sensitive electronics in your car from potential damage caused by voltage spikes or surges. The relay acts as a switch, directing the current efficiently to safely jump-start your vehicle's battery.

Diagram showing how a jump starter relay works

Benefits of Using a Relay

Safer: Reduces the risk of damaging your car's electronics.
More efficient: Provides a more consistent and reliable jump start.
Easier to use: Simplifies the jump starting process with clear connections.

Step-by-Step Instructions for Jump Starting with a Relay

Step 1: Gather Necessary Materials

Jump starter relay
Jumper cables (heavy-duty recommended)
A vehicle with a working battery (the "booster" car)
Safety glasses or goggles (always a good idea)

Step 2: Prepare Both Vehicles

Park both vehicles close together, ensuring that they don't touch. Turn off both vehicles' engines and engage their parking brakes. Locate the positive (+) and negative (-) terminals on both batteries. Note: Consult your car's manual to find the battery location if you're unsure.

Step 3: Connect the Relay

Connect the relay according to the manufacturer's instructions. Generally, this involves attaching the relay's clamps to the positive and negative terminals of both the dead and booster batteries. Pay close attention to the polarity (+ and -). Incorrect connections can damage the electronics.

Step 4: Connect Jumper Cables to the Relay

Connect the jumper cables to the relay's designated terminals. The relay will have specific connection points for the jumper cables, usually clearly labeled. Again, ensure correct polarity.

Image showing jumper cable connections to the relay

Step 5: Start the Booster Car

Start the booster car's engine and let it run for a few minutes to ensure the battery is fully charged. This charges up the relay circuit before attempting to start the dead vehicle.

Step 6: Attempt to Start the Dead Car

Try to start the dead car. If it doesn't start immediately, let the booster car run for a few more minutes to allow more charge to transfer. If the car still doesn't start, there may be a more serious issue with the battery, alternator or starter motor, and professional help might be needed.

Step 7: Disconnect Everything

Once the dead car has started, remove the jumper cables from the relay, and then disconnect the relay from both batteries. Always disconnect the negative cables first, and then the positives.

Step 8: Let the Car Run

Allow the dead car to run for at least 30 minutes to allow the battery to recharge somewhat. This helps prevent it from dying again immediately.

Troubleshooting

If you encounter any problems, such as the dead car not starting or sparks while connecting cables, carefully review your connections and ensure correct polarity. If issues persist, consult the relay manufacturer's instructions or seek professional assistance.

Safety Precautions

Always wear safety glasses or goggles.
Never allow jumper cables to touch each other.
Be cautious of moving parts in the engine bay.
If unsure, consult a qualified mechanic.

Conclusion

Jump starting a car with a relay is a safer and more efficient method compared to traditional jumper cable methods. Following these steps and prioritizing safety will help you get back on the road quickly and confidently. Remember, if you're not comfortable performing this procedure, seeking professional help is always the best option.