The key turns. In the deep quiet of a deserted parking garage or on your driveway, the dashboard lights strain, flicker once, and die. A heavy silence fills the car and leaves you feeling stuck and frustrated. What happens in the next 10 minutes depends entirely on the driver's knowledge. Knowing how to jump a battery gets you back on the road quickly. Aside from that, knowing when to replace the car battery can avoid ending up completely stuck.
For many drivers, the solution could be even simpler. A AAA membership puts professional help just a phone call away. The easiest first step for a member with a dead battery is to contact AAA Roadside Assistance and let them handle the ordeal for you. For those who want to do it themselves, however, you can lean on this guide to help you through the entire process.
1. Safety First: Before You Jump a Battery
When you're first learning how to jump a car battery, you need to understand that there are safety concerns to be aware of. The next few moments of inspection are what separate a simple five-minute fix from a dangerous and expensive mistake:
- Check the dead battery for any cracks or bulging sides. A strong smell of rotten eggs is a clear warning sign of leaking sulfuric acid and potentially explosive hydrogen gas. You must replace a damaged battery, not jump it.
- Confirm that both vehicles use a 12-volt battery by checking the voltage printed directly on the battery's label. Connecting a 24-volt system from a commercial truck to a car's electronics can cause immediate and expensive damage.
- Check that the car is in park or neutral with the parking brake set firmly to prevent it from rolling. The engaged brake also serves as a failsafe against any unexpected lurch from the starter motor.
- Position the cars so that the jumper cables can easily reach from one battery to the next, but make sure that both ignitions are completely off to prevent a voltage spike.
- Remove any metal jewelry, especially rings and watches. Accidentally touching a tool from the positive terminal to a metal ring can cause a severe burn or a dangerous short circuit.
2. Gather Your Equipment
The equipment for a jump-start matters as much as the procedure. You'll need to check that you have the following tools for the job:
- Cheap, thin jumper cables are a frequent point of failure, especially with larger V6 or V8 engines or in below-freezing temperatures. Look for a heavy-duty set of six-gauge, 16-foot cables.
- Safety glasses aren't optional. A faulty battery can vent explosive hydrogen gas, and in a worst-case scenario, these glasses are the only thing protecting a person's eyes from flying acid and plastic shrapnel.
- Wear gloves to protect against potential electric shock or contact with battery acid. Insulated gloves are best for providing a barrier against a shock.
- Almost any running car with a healthy battery will work, but the best choice is one with a battery of similar or larger size. Most hybrid and electric vehicles, however, have complex electronics that can be destroyed by jump-starting another car.
3. Position the Vehicles
Get the cars close enough for the cables to reach, but leave a few inches of air between them to protect them should the one car lunge. On a busy highway, personal safety comes first, so do not jump-start the car if there isn't enough room to work clear of traffic or if visibility from darkness or fog is poor.
In a cramped garage, save yourself a headache by popping both hoods to check the battery terminal locations first before you position the vehicles. A simple step like this avoids the frustration of realizing the cables won't reach.
4. Attach the Jumper Cables
Connecting the jumper cables correctly is important, as you'll want to avoid any potential sparks. The recommended order for how to connect jumper cables is a professional one designed to keep sparks far away from the battery:
- First, take one red clamp and connect it firmly to the positive (+) terminal of the dead battery.
- Attach the other red clamp to the positive (+) terminal of the working vehicle's battery.
- Next, connect one black clamp to the negative (-) terminal of the good battery.
- The last connection is to attach the final black clamp to a clean, unpainted piece of metal on the car with the dead battery, like a thick bolt on the engine block. The bolt itself becomes the grounding point, directing the small, final spark safely away from the battery and any potential fumes.
- Do a quick final check to see that the cables aren't draped over any moving parts. Keep them clear of any belts or fans before trying to start the car.
5. Start the Working Car First
With the cables all connected, go ahead and start the engine of the working car. Its alternator does the real work here, sending a steady charge through the cables to the dead battery. Give it a solid three to five minutes before you attempt to start the dead car's battery to build up a surface charge.
Holding the engine rev slightly above idle helps the alternator work faster, a useful trick on a cold winter morning.
6. Try Starting the Dead Car
The sound the dead car makes when the key is turned tells the whole story. A car that starts right away is a sign that the battery is still healthy, and that the procedure for how to jump-start a car was a success. A slow, struggling crank is a sign of progress, while a sharp, repeated click often points to a more serious issue.
If the engine turns over slowly, don't keep trying. Instead, let the working car charge it for another five minutes before making one final attempt. A car that still won't start after a third try likely has a completely failed battery that needs a full replacement. If it can start, take it to a repair shop right away or find a parts store with your type of battery if you know how to change a battery yourself.
7. When Your Car Restarts¦
Hearing the engine turn over is a huge relief, but the job isn't quite finished. The next few steps are needed to make sure the car stays running and address the reason it failed in the first place.
For starters, let both cars run while still connected for another three to five minutes, as that'll give the newly running electrical system a moment to stabilize. Then, disconnect the cables in the exact reverse order of how they were connected. Start with the black clamp on the grounding point, then the black clamp from the donor car, followed by the red from the donor, and finally the red from the car that was just started.
A jump-start often doesn't equal a charged battery. The alternator needs time and sustained engine running to properly recharge the battery. A continuous drive of 20 to 30 minutes is usually enough to get the job done. During this drive, keep high-load items like the air conditioner and rear defroster off to give the weak system its best chance at recharging.
It's important to note that a short drive won't save an old battery. If the battery is more than three years old or has been struggling, it likely won't hold a charge overnight. The smartest move is to drive the car straight to a local shop, such as an AAA Approved Auto Repair Facility, to have the battery properly tested. Members can also use AAA's Mobile Battery Service, and anyone can purchase an AAA Battery at NAPA Auto Parts stores. Routine car battery maintenance is the best way to avoid an expensive situation altogether.
Troubleshooting a Jump Start
A jump-start that fails after following the proper steps is frustrating, but it also gives valuable information. The failure itself helps point toward the real root of the problem:
- The most common reason for a failed jump is a poor connection. The clamp's teeth must bite into clean, bare metal, as even a thin layer of whitish-blue terminal corrosion can stop electricity from flowing. Disconnect the cables safely and use a wire brush to scrub the posts clean before another try.
- If that doesn't work, take a close look at the jumper cables for obvious problems like frayed wires. The more hidden issue, however, is often internal corrosion on old or cheap cables, which can prevent them from carrying enough power.
- A jump-start can't revive a battery that's simply too old to hold a charge. Knowing how long car batteries last is important because one that's too old has likely failed internally and needs a full replacement.
- Listen for clues that point to a different problem. A single click sound when the key is turned, especially if the dashboard lights are bright, often means the issue is a bad starter motor, not the battery itself. Note: Rapid clicking when the key is turned generally indicates a battery issue.
- Finally, acknowledge when to stop guessing. If these simple checks do not solve the problem, the smartest move is to call for professional roadside help, to get an expert diagnosis instead of risking more damage.
When it's Not Your Battery
Sometimes, a car that refuses to start has a perfectly healthy battery. The symptoms of a failed jump-start often point to a different problem entirely within the car's electrical system.
The single click sound from the troubleshooting section, for example, almost always indicates a failing starter motor. This repair requires a mechanic and has its own starter replacement cost.
Another common culprit is a bad alternator. If the car starts with a jump but dies again after a short drive, the alternator is likely not recharging the battery, a classic sign of a bad alternator vs. a bad battery problem.
Problems with starters and alternators aren't simple roadside fixes. Once the issue is clearly something other than the battery, the wisest move is to stop and make a phone call. Services like AAA Roadside Assistance can dispatch a professional to diagnose and help you fix the problem correctly and safely.
Conclusion
For the next few days after jump-starting your battery, turning the key is different. There's a moment of hesitation, a hope the engine catches, a fear that it won't. Knowing how to jump a battery is a powerful safety net in those moments, but it's not a permanent solution for a failing battery.
That feeling of uncertainty only disappears with a healthy battery. A battery near the end of its three-to-five-year lifespan is living on borrowed time. Deciding to replace it is the final step, and that step starts with a car battery quote to see the real cost and move toward a reliable start, every time.
For added convenience, AAA's car battery replacement service can even bring a new battery to you and install it on the spot.
FAQ
Even with a step-by-step guide, a few specific questions always come up.
Can a car battery be so dead it won't jumpstart?
Yes, a battery with a shorted internal cell or one that is simply too old has lost its ability to store energy. A jump-start sends power, but it cannot fix a battery that's chemically dead.
How long does it take to jumpstart a battery?
The entire process of jump-starting a car battery typically takes about 10 to 15 minutes. That time frame includes the important three-to-five-minute charging period before the first attempt to start the car.
How do I know what battery to buy for my car?
The owner's manual lists the exact battery a car needs, including the group size and required Cold Cranking Amps (CCA). With it, you will know which of the various car battery types is the best option for your vehicle and driving habits. A reputable auto parts store or workshop can also find the correct one using the car's make, model and year.
Is red positive or negative on jumper cables?
The red clamp on jumper cables is always for the positive (+) terminal. A good way to remember is the phrase red to positive, black to negative, although the final black connection should be to a grounding point, not the dead battery.