Learning how to jumpstart a car with another car is a fundamental skill every driver should have. A successful jumpstart with a helper car relies on creating a safe, temporary circuit between the two batteries. This guide provides clear, step-by-step instructions to get you back on the road quickly and safely.
How To Jumpstart A Car With Another Car
This process, also known as a jump start or a boost, involves using a functional vehicle’s battery to provide the necessary power to start an engine with a dead battery. It’s a straightforward procedure when done correctly, but safety is paramount. Following the right order of operations prevents damage to either vehicle’s electrical system.
Essential Tools And Safety Precautions
Before you connect any cables, you need the right equipment and a safe environment. Never attempt a jumpstart without these items and checks.
What You Will Need
- A set of heavy-duty jumper cables with thick, insulated wires and clean, rust-free clamps.
- A helper car with a battery that has the same voltage as your car’s battery (almost always 12 volts).
- Safety glasses and gloves are highly recommended.
Critical Safety Checks
- Inspect both batteries. If you see cracks, leaks, or corrosion, do not proceed. A damaged battery can release harmful gases or acid.
- Ensure the vehicles are not touching each other and are in Park (automatic) or Neutral (manual) with the parking brakes firmly engaged.
- Turn off all accessories in both cars, including lights, radio, and climate control.
- Work in a well-ventilated area to avoid buildup of potentially flammable gases from the battery.
Step-By-Step Jumpstart Procedure
Now that you’re prepared, follow these steps in exact order. The sequence is crucial for preventing sparks and electrical surges.
- Position the Helper Car: Drive the working car so it faces the disabled car, but ensure they do not touch. Leave enough space to comfortably attach the jumper cables between the two batteries.
- Open the Hoods and Locate Batteries: Pop the hoods on both vehicles and secure them. Identify the positive (+) and negative (-) terminals on each battery. They are usually clearly marked with red for positive and black for negative.
- Connect the Red Jumper Cable Clamp to the Dead Battery’s Positive Terminal: Attach one of the red (positive) clamps to the positive terminal of the dead battery. Ensure it has a solid metal connection.
- Connect the Other Red Clamp to the Good Battery’s Positive Terminal: Attach the other red clamp to the positive terminal of the helper car’s live battery.
- Connect the Black Jumper Cable Clamp to the Good Battery’s Negative Terminal: Attach one of the black (negative) clamps to the negative terminal of the good battery.
- Connect the Final Black Clamp to an Unpainted Metal Surface on the Dead Car: This is the most important safety step. Do NOT connect this final black clamp to the dead battery’s negative terminal. Instead, attach it to a solid, unpainted metal part of the engine block or the car’s frame. This provides a safe ground and minimizes the risk of sparking near the battery.
- Start the Helper Car: Start the engine of the helper car and let it run for a few minutes. This allows its alternator to begin charging the dead battery.
- Attempt to Start the Dead Car: Try to start the car with the dead battery. If it doesn’t start immediately, wait another minute or two with the helper car running, then try again. Do not crank the starter for more than 5-10 seconds at a time.
- If Successful, Carefully Disconnect the Cables in Reverse Order: Once the disabled car is running, carefully remove the jumper cables in the exact reverse order you put them on.
- Disconnect the black clamp from the grounding point on the revived car.
- Disconnect the black clamp from the helper car’s negative terminal.
- Disconnect the red clamp from the helper car’s positive terminal.
- Disconnect the red clamp from the revived car’s positive terminal.
- Keep the Revived Car Running: Do not turn off the engine of the car you just jumpstarted. Drive it for at least 20-30 minutes to allow its alternator to recharge the battery fully.
What To Do If The Car Still Won’t Start
If you’ve followed the steps correctly and the car still won’t start, the problem may not be a simple dead battery. Here are a few common issues.
- Check Cable Connections: Double-check that all four clamps are secure and making good metal-to-metal contact. A loose clamp is a frequent culprit.
- Try a Different Grounding Point: If you grounded the final black clamp on a painted surface, find a better, bare metal spot.
- The Battery May Be Too Old or Damaged: Batteries typically last 3-5 years. An old battery may not hold a charge at all and will need replacement.
- Alternator or Starter Problems: A faulty alternator won’t charge the battery, and a bad starter motor won’t crank the engine even with power. You may hear a clicking sound if the starter is failing.
- Blown Fuse: Check your car’s main fuse box for any blown fuses related to the starting or charging system.
Aftercare And Battery Health
A successful jumpstart is only a temporary fix. You need to adress the underlying cause of the dead battery to prevent it from happening again.
Diagnosing The Cause Of The Dead Battery
Ask yourself a few questions to figure out why the battery died. Did you leave an interior light or headlights on overnight? Have you only been taking very short trips recently, which doesn’t give the alternator enough time to recharge the battery? Is there a parasitic drain from an aftermarket accessory? If the battery is more than four years old, it may simply be at the end of its lifespan.
Getting Your Battery Tested
Most auto parts stores offer free battery and alternator testing. After your drive, visit a shop to have them test the battery’s health and the alternator’s output. This will tell you definitively if the battery needs to be replaced or if there is another issue with the vehicle’s charging system.
Common Mistakes To Avoid
Even with good intentions, simple errors can lead to problems. Be sure to steer clear of these common pitfalls.
- Connecting Cables in the Wrong Order: Always connect positive to positive first, and ground the final negative clamp to the car’s body, not the battery.
- Letting the Clamps Touch: Once the cables are connected, be careful not to let the positive and negative clamps touch each other, as this creates a dangerous short circuit.
- Using Damaged or Thin Cables: Cheap, thin jumper cables can overheat and melt. Invest in a good quality set with thick, 4-gauge or 6-gauge wires.
- Turning Off the Jumpstarted Car Too Soon: Shutting off the engine immediately after a jumpstart will likely leave you with a dead battery again, as it hasn’t had time to recharge.
- Ignoring Warning Signs: If you notice your headlights dimming or the car is slow to crank on a regular basis, get your battery tested before it fails completely.
FAQ Section
Here are answers to some frequently asked questions about jumpstarting a vehicle.
Can you jumpstart a car in the rain?
Yes, you can jumpstart a car in the rain. Modern batteries are well-sealed, and the voltage involved is relatively low. However, you should take extra care to keep the cable connections as dry as possible and avoid standing in puddles. If the weather is severe with heavy rain or lightning, it is safer to wait or call for professional assistance.
How long should you leave the cables connected before starting?
After making all four connections, let the helper car run for about 3-5 minutes before attempting to start the dead car. This allows some charge to transfer to the dead battery, giving it enough power to crank the starter motor. If the battery was completely drained, it may need a few more minutes.
What if my car has a special electronic system or is a hybrid?
Many modern cars, especially hybrids and those with start-stop systems, have specific procedures or dedicated jump-starting points under the hood. Always consult your owner’s manual first. Connecting cables directly to the battery in some of these vehicles can damage sensitive control units. The manual will show you the correct positive terminal and grounding point to use.
Is it possible to jumpstart a car without another car?
Yes, you can use a portable jump starter or battery booster pack. These compact devices contain a rechargeable battery and have built-in clamps. You simply connect them directly to your car’s battery following the same safety order, without the need for a second vehicle. They are a convenient tool to keep in your trunk.
Why did my car start but then die again after I removed the cables?
If the car starts with the jumper cables connected but stalls once they are removed, the problem is likely not the battery itself. This usually indicates a failing alternator. The alternator’s job is to charge the battery while the engine runs. If it has failed, the car is running solely on the battery’s charge, which depletes quickly, causing the engine to shut off.