A jump start usually takes 5 to 10 minutes from the moment you connect the cables
The actual time to jump-start a car breaks into two parts: connecting the cables and letting the battery charge. Connecting takes about 2 to 3 minutes if you know where the battery terminals are. Charging takes another 3 to 5 minutes of the donor car running before you try to start your own vehicle. If your car starts on the first try, you are done. If it does not, you may need another 2 to 3 minutes of charging before trying again.
The total time also depends on how dead your battery is. A battery that is partially drained might start in 3 to 5 minutes of charging. A battery that is completely dead can take 10 to 15 minutes or longer. Cold weather makes this slower because chemical reactions in the battery slow down in freezing temperatures.
After your car starts, you should leave both cars running for another minute or two before disconnecting the cables. This gives your alternator time to begin recharging your battery. Disconnecting the cables takes about 1 to 2 minutes.
Key Takeaways
- Connecting jumper cables and charging your battery takes 5 to 10 minutes in normal conditions, longer in cold weather or if your battery is completely dead.
- Let the donor car run for 3 to 5 minutes before you try to start your car, and wait another minute after it starts before disconnecting the cables.
- If your car does not start after 5 minutes of charging, wait another 2 to 3 minutes and try again rather than repeatedly turning the key.
- After a successful jump start, drive for at least 20 minutes to let your alternator recharge the battery enough to start the car again later.
Why the time varies: battery condition and temperature
A battery that has been slowly draining over days or weeks will jump-start faster than one that died suddenly from leaving lights on overnight. A slow drain means the battery still has some charge left, so it needs less time to reach the voltage needed to start the engine. A completely dead battery starts from near zero and needs more charging time.
Cold weather is the biggest factor in longer jump-start times. Below freezing, a battery's chemical reactions slow dramatically, and the engine itself is harder to turn over. A jump start that takes 5 minutes on a 70-degree day might take 15 minutes at 20 degrees. In extreme cold, you may need to let the battery charge for 20 minutes or more.
The size and condition of the donor car also matters. A large truck or SUV with a healthy battery can deliver more current and charge your battery faster than a small sedan with an older battery. A damaged or corroded battery terminal can also slow the process because it reduces the flow of electricity between the cars.
The step-by-step timeline for a jump start
Here is what actually happens during those 5 to 10 minutes:
- Minutes 0 to 1: Park the donor car close to yours (within 18 inches), turn off both engines, and locate both batteries. Open the hoods and find the positive and negative terminals on each battery.
- Minutes 1 to 2: Connect the red (positive) cable to the positive terminal of your dead battery, then to the positive terminal of the donor battery. Connect the black (negative) cable to the negative terminal of the donor battery.
- Minutes 2 to 3: Connect the black cable to an unpainted metal surface on your engine block, away from the battery. Do not connect it directly to the negative terminal of your dead battery — this reduces the risk of sparks.
- Minutes 3 to 8: Start the donor car and let it run. Your battery is charging during this time. Wait at least 3 to 5 minutes before trying to start your car.
- Minute 8 to 9: Try to start your car. If it starts, leave both cars running for 1 to 2 minutes.
- Minutes 9 to 10: Disconnect the cables in reverse order: black cable from your engine, black cable from the donor battery, red cable from the donor battery, red cable from your battery.
If your car does not start after 5 minutes of charging, do not keep turning the key. Repeated attempts drain the battery further and can damage the starter. Instead, wait another 2 to 3 minutes and try once more.
What happens if the jump start does not work
If your car still will not start after 10 to 15 minutes of charging, the battery may be too damaged to jump-start, or the problem may not be the battery at all. A faulty alternator, a bad starter motor, or a fuel system problem can all prevent a car from starting even with a full charge.
At this point, you have a few options. You can try a second time with a different donor car, in case the first car's battery was not strong enough. You can call a roadside service like AAA, which has specialized equipment that can charge a battery faster than jumper cables. Or you can have the car towed to a mechanic to diagnose the real problem.
If you do call for roadside help, tell them you have already tried a jump start. This helps them bring the right equipment and know what to expect when they arrive.
How to keep your battery charged after a jump start
After your car starts, your alternator begins recharging the battery, but it needs time to build up enough charge for the next start. Drive for at least 20 to 30 minutes at highway speeds if possible. City driving with frequent stops does not charge the battery as quickly because the engine is not running at full power.
If you only drive for 5 or 10 minutes and then turn off the engine, the battery may not have enough charge to start the car again. This is especially true if you then run the headlights, radio, or air conditioning while parked.
After a jump start, have the battery tested within a few days. A battery that needed a jump start may be nearing the end of its life, even if it starts the car again. A battery test at an auto parts store or mechanic is usually free and takes about 10 minutes. If the battery is weak, replacing it now prevents you from being stranded again.
Jump starting in different weather conditions
Cold weather slows everything down. In freezing temperatures, increase your charging time to 10 to 15 minutes before trying to start. The battery has less power, and the engine is harder to turn. You may also need to pump the gas pedal gently once or twice after the engine starts to help it stay running.
Hot weather is less of a problem for jump-starting, but it does speed up the process slightly. A battery charges faster in warm conditions, so you might be ready to start in 3 to 4 minutes instead of 5. However, heat can also damage a battery over time, so if you are jump-starting in summer heat, have the battery tested soon.
Rain or wet conditions do not slow down a jump start as long as the battery terminals and cables are dry. Wipe them with a clean cloth before connecting if they are wet. Wet cables can cause sparks, so take a moment to dry them.
Frequently Asked Questions
Can I jump-start a car by myself, or do I need another person?
You can do it alone. You need another car and driver to start the donor vehicle, but once it is running, you can return to your own car and attempt to start it. The only time a second person is truly helpful is if you are not sure where your battery terminals are and need someone to hold a flashlight or look at the manual while you work.
What if I do not have jumper cables?
You cannot jump-start without cables. If you do not have them, call roadside help or a tow truck. Some people carry jumper cables in their trunk, but if you do not have them and cannot borrow a set, a professional service is your only option. Roadside services usually arrive within 30 minutes to an hour in urban areas.
Is it safe to jump-start a car with a cracked or leaking battery?
A cracked battery can leak acid and is not safe to jump-start. If you see cracks, fluid leaking, or a bulging case, do not attempt a jump start. Call for roadside help instead. A damaged battery can cause burns or damage to your car's electrical system.
How many times can I jump-start the same car before I need a new battery?
If you need a jump start more than once or twice a year, the battery is probably failing and should be replaced. A healthy battery rarely needs a jump start. If you are jump-starting the same car repeatedly, the battery is nearing the end of its life, and a replacement will save you time and frustration.
Can I jump-start a car with a dead alternator?
A jump start will not fix a dead alternator because the alternator is what charges the battery while the engine runs. If your alternator is not working, the battery will drain again as soon as you turn off the engine. You can jump-start to get to a mechanic, but you will need the alternator repaired or replaced to solve the problem.