How to Jump-Start a Car With Jumper Cables Safely

Jump-starting uses a working vehicle’s battery to provide enough power for a car with a weak battery to start. It does not repair a damaged battery or charging system. Before you begin, check both vehicles’ owner’s manuals: some cars require designated jump points or have specific procedures. Never proceed if the manuals prohibit a jump-start or if you are unsure about the connection points.

What You’ll Need

A set of insulated jumper cables in good condition, with clamps that are clean and undamaged.
A vehicle with a compatible electrical system and a charged battery. Check both manuals for voltage and jump-start compatibility; do not assume that any vehicle is suitable.
Safety glasses, if available, and gloves. Keep jewelry, loose clothing, and hands away from moving engine parts.
A well-ventilated location away from traffic, flames, cigarettes, and sparks. Do not jump-start a vehicle in an enclosed garage.

Step-by-Step

Park and prepare. Position the donor vehicle close enough for the cables to reach, but do not let the vehicles touch. Put both in Park, or Neutral for a manual transmission, apply the parking brakes, and switch off both ignitions and all lights and accessories. Keep the keys or fobs away from the vehicles while connecting.
Inspect the disabled battery. Do not jump-start a battery that is cracked, leaking, swollen, unusually hot, frozen, or giving off a strong sulfur-like odor. Do not touch battery fluid. If you see corrosion, damage, or loose parts, stop and seek roadside assistance or a qualified mechanic instead.
Find the correct terminals and ground point. Identify the positive (+) and negative (−) terminals on each battery, or the manufacturer-designated remote jump points. Use the manual to locate an approved unpainted metal grounding point on the disabled vehicle’s engine or chassis, away from the battery, fuel components, belts, and fans. Never guess at a connection point.
Connect the first red clamp. Attach one red clamp to the disabled car’s positive (+) terminal or designated positive jump point. Make sure it grips securely and cannot swing into metal.
Connect the second red clamp. Attach the other red clamp to the donor vehicle’s positive (+) terminal or designated positive point. Keep the free clamps from touching each other or any metal.
Connect the first black clamp. Attach one black clamp to the donor vehicle’s negative (−) terminal or the negative point specified in its manual.
Make the final connection to ground. Attach the remaining black clamp to the approved unpainted metal ground on the disabled vehicle—not to its negative battery terminal unless the manufacturer specifically instructs otherwise. This places the final connection away from the battery, reducing the risk of a spark near battery gases. Keep the cables clear of moving or hot parts.
Start the donor vehicle. Start it and let it run at a normal idle for a few minutes, following the manuals’ instructions. Do not rev the engine unless the manufacturer specifically directs it. If a clamp shifts, a cable becomes hot, or you notice smoke or sparking, switch both vehicles off if safe and stop.
Try the disabled car. Start it using its normal procedure. If it does not start after a short attempt, stop and wait briefly before trying again. Repeated or prolonged cranking can overheat the starter and cables. Do not keep trying if you hear unusual noises or see warning signs.
Remove the cables in reverse order. Once the car starts, leave it running and remove the clamps without letting them touch: first the black clamp from the disabled car’s ground, then the black clamp from the donor, followed by the red clamp from the donor and the red clamp from the started car. Keep clamps clear of moving parts as you remove them.
Let the car run and arrange a check. Follow the owner’s manual on how long to run or drive the vehicle after a jump. A jump-start may not fully recharge the battery. If the car stalls, will not restart, or the battery warning light stays on, arrange a battery and charging-system check rather than relying on another jump.

Common Mistakes

Reversing polarity: Connecting positive to negative can cause sparks and severe electrical damage. Confirm the + and − marks before every clamp goes on.
Putting the final black clamp on the wrong place: Use the vehicle’s specified ground point. Do not clamp onto painted, thin, or moving parts, fuel lines, or a random bolt.
Letting clamps touch: Keep loose clamps separated and away from bodywork. Do not lean over the batteries while making connections.
Starting too soon: Make sure all four clamps are secure and correctly placed before starting either vehicle.
Ignoring damage or manual instructions: A jump is not appropriate for every battery or vehicle. Stop if the battery is damaged or the manufacturer specifies another procedure.
Disconnecting in the wrong order: Remove clamps in reverse order, starting with the disabled vehicle’s ground connection. Never pull cables free while either engine is running.

Tips

Read both owner’s manuals before connecting anything; hybrid and electric vehicles may have special jump-start points or restrictions. Never use an electric vehicle’s high-voltage components as a jump source.
Use only cables rated and long enough for the vehicles, and keep the clamps’ metal jaws from contacting each other.
Keep children and bystanders away. Avoid smoking, open flames, and anything that could create a spark around a battery.
If the car starts, do not assume the battery is healthy. A battery that repeatedly goes flat needs professional inspection; the cause could be the battery, charging system, or an electrical drain.
If a donor vehicle is unavailable, a suitable portable jump starter can be an alternative, but follow its instructions and the vehicle manual.

Troubleshooting

The car does not crank: Switch both vehicles off and recheck the cable order, terminal markings, clamp grip, and approved ground point against the manuals. Do not reposition clamps while either vehicle is running. If connections are correct, the battery may be too damaged or depleted to accept a jump, or there may be another fault; call roadside assistance.

It clicks but will not start: A clicking sound can indicate insufficient power or a separate starter or electrical problem. Stop after a few short attempts. Do not keep cranking or increase engine speed to force a start.

It starts, then stalls or will not restart: The battery may not be holding a charge, or the charging system may not be working. Avoid switching off in an unsafe location, and arrange professional assistance and testing.

You see sparks, smoke, or a hot cable: Stop immediately. If safe, switch off the engines and do not touch hot cables or battery fluid. Move away and call for assistance if there is smoke, fire, or a damaged battery.

There are no clear jump points: Do not guess. Check the manuals or contact roadside assistance or the vehicle manufacturer.

Frequently Asked Questions

Can I jump-start a car in the rain?

Light rain does not by itself make a correctly performed jump-start impossible, but avoid standing water, wet or damaged equipment, and exposed electrical connections. If conditions make it hard to work safely, wait for assistance.

How long should I leave the donor car running?

Follow the vehicle manuals. A short period at idle may help provide power, but there is no single time that suits every vehicle or battery. Do not rev the donor unless its manufacturer instructs you to.

Can I connect the black clamp to the dead battery’s negative terminal?

Use the disabled vehicle’s designated ground point as the default. Connect to its negative terminal only if that vehicle’s manual specifically directs you to do so.

Why should I connect the last clamp to metal ground?

Making the final connection away from the battery helps keep a connection spark away from gases that may be present around it. The ground must be a point approved by the vehicle manufacturer.

Will jump-starting recharge the battery?

It may add some charge, but it does not guarantee a full recharge or fix a failing battery. Have the battery and charging system checked if the problem returns or the vehicle will not restart.

Can I jump-start a hybrid or electric car?

Some have a 12-volt battery and designated jump points, while procedures vary by model. Follow the manual exactly, and never use high-voltage components or assume the vehicle can serve as a donor.

Further reading: National Highway Traffic Safety Administration (NHTSA). Details can change, so check the official page for anything that matters to you. Spotted a mistake? Tell us. How we write an answer.