Your battery may be too weak to start your car for a number of reasons, including because the battery has been discharged due to cold weather, wear and tear, or because you left the lights on at night. Whatever the cause, you can use jumper cables to connect the dead battery to a live battery. Make sure that both batteries are the same size, then carefully begin to clamp the cables in place. The empty battery can then receive enough charge to start the car again.
Steps
Part 1 of 3: Exposing the battery
Step 1. Park the vehicles so that the batteries are close to each other
Drive the vehicle with the full battery, the donor car, to the vehicle with the empty battery. The battery is usually located under the hood of the car, so you can park the cars side by side or opposite each other. Don't let the cars touch each other though!
If you can't find the battery, see the owner's manual
It should tell you where the battery is and how to get to it.
Step 2. Engage the parking brake of both cars
The handbrake keeps the cars in place while you connect the battery. Use the gear lever if your car has one. Shift the car to 'P' or 'Park' to apply the brake. Putting the car in 'N' or 'Neutral' also prevents the car from rolling. If your car has a manual transmission, put it in neutral and then apply the emergency brake.
The emergency brake may be located near the gear lever or accelerator pedal
Step 3. Turn off the cars and remove the keys
Make sure the donor car is completely turned off. You should hear the engine stall and you can test the radio to see if there is no power to it. Also remove the key from the car with the dead battery so that it cannot start with the jumper cables attached.
This protects both motors from power surges and reduces the risk of electric shock
Step 4. Check the batteries to make sure they have the same voltage
The voltage is displayed in a visible place, usually on a white or yellow sticker on top of the battery. It will then read something like '12V'. The voltage of the battery must match that of the depleted battery, otherwise the battery could release a dangerous current that could burn out the car's systems.
- Batteries with similar voltages will be the same size. However, check the voltage rating on the label to avoid possible damage.
- If you're not sure about using a battery, don't take any chances, if possible. Try to find another donor battery or use a rechargeable battery.
Step 5. Locate the positive and negative battery terminals in each car
The leads leading to the positive terminal are almost always red. The cables from the negative terminal are black. If you are not sure, there is a '+' and a '-' sign on the battery to indicate the positive and negative terminal respectively. The red wires go to the '+' terminal and the black wires to the '-' terminal.
First check the connections for corrosion. Corrosion looks like white, green and blue powder. Clean the connections by wiping them with a cloth or wire brush
Part 2 of 3: Connecting the cables
Step 1. Separate the terminals from the jumper cables by laying them on the floor
Lay the cables flat on the ground and stretch them out between the two cars. Make sure the clamps do not touch each other. Any contact can cause a short circuit in your car's electrical system.
The wires of jumper cables are often different in length, to prevent them from touching each other. If they are the same length, check that they have not been altered or damaged in any way
Step 2. Connect a red clamp to the positive terminal of the empty battery
Leave the rest of the jumper cable on the ground as you bring the clamp to the car. Check the '+' and '-' labels on the battery before attaching the clamp. Squeeze the clamp to open it, then fit it securely around the metal contact.
- Some vehicles require you to remove a plastic cover from the positive battery terminal before making the connection. You remove the cover by turning it counterclockwise by hand.
- Connect each terminal one at a time. Proceed slowly to avoid mistakes that could damage the vehicles.
Step 3. Connect the other red clamp to the positive terminal of the donor battery
Take the clamp with you to the other car so that you can mount it on the correct clamp. Make sure it is securely fastened so that it does not slip off when the motor is activated later.
Remember to connect red to red and the positive poles to each other, just connecting the red terminals
Step 4. Connect a black clamp to the negative terminal of the donor battery
Take out the black clip and return it to the live battery. The black clamp fits directly onto the '-' terminal on the battery. As long as he doesn't touch the '+' pole or the red clamp, there's nothing to worry about.
If you tighten a clamp the wrong way round, stop before starting the cars. Carefully remove the clamps, working one at a time, to avoid touching each other
Step 5. Clamp the other black cable to an unpainted metal surface in the car
The black clamp is not connected to a battery terminal. Instead, find a spot such as a clean bolt in the engine block. You can also place the clamp on an unpainted part of the car body under the hood.
- Do not connect this clamp to the empty battery unless you have no other choice. This otherwise produces a spark that can ignite hydrogen vapors after the car is turned on.
- Don't dig too far down to find a metal surface. The fuel lines are down there and you better keep the clamp out of the way.
- Make sure that the jumper cable is not hanging in the engine compartment, as it can be caught there by moving parts.
Part 3 of 3: Starting the car
Step 1. Start the donor vehicle and let it idle for a few minutes
Use the ignition key to start the engine. The electrical systems, such as the lights and the radio, will start as the electricity flows to the depleted battery. Give the battery at least 30 seconds to build up charge before attempting to start the other car.
- Depending on the age and condition of the battery, charging may take longer.
- Hit the accelerator to build up the RPM to around 3000, if you want to send more power to the dead battery.
Step 2. Turn on the car engine with the dead battery
Turn the key in the ignition to turn the car on. Immediately the electrical systems should activate. If the lights, radio, or other electrical parts don't come on, you may need to give the battery more time. Turn off the car, check that the cables are securely attached, and then try to rev the working car to increase the power supply.
- If the car does not start after repeated attempts, your car may have a different problem. It could have a blown fuse.
- If the car's lights are on but the engine won't start, the battery is fine. You can hear the engine make a clicking noise when you try to start it. This could be related to a faulty starter motor.
Step 3. Disconnect the jumper cables in reverse order, starting with the black terminals
Remove the cables in the exact reverse order as before. Start with the negative ground lead that you attached to a metal part. Remove the black clip on the donor battery, followed by the red clip. Finally, remove the red clamp from the battery that has just been charged.
- Let the car run so that it has time to charge further, otherwise you will have to recharge it with another battery.
- Be careful with the cables. Make sure that the clamps do not touch each other until they are all removed from the batteries.
Tips
- Some cars have batteries under the back seat or in the trunk of the car. These cars may also have a jump port under the hood. This is usually indicated by a red lid with a '+' on it. Clip on the red jumper cable after removing the cover.
- Some vehicles have plastic covers all over the battery that you have to remove before you can attach the cables. You can remove these by prying or unscrewing them.
- Shorter cables usually work better because the electrical current has to travel less distance. Longer cables can lead to weaker currents and longer charging times.
- Drive a freshly charged car for at least 15 minutes to recharge the battery.
- Get a rechargeable battery for jump-starts so you don't need another car. You keep the battery charged via the USB port, and connect the jumper cables to it as you normally would when you have an empty battery.
Warnings
- Avoid jump-starting a frozen battery as it may explode. If you can open the battery, see if the liquid in the battery is frozen. If the side of the battery is bulging, it is probably frozen.
- Car batteries emit explosive hydrogen gas, so do not smoke near a battery. Also make sure that the black ground cable is not connected to the negative terminal of the empty battery.