Hook up Jumper Cables
Your car battery could be too weak to start your car for a number of reasons: faulty alternator, leaving the lights on, cold weather, or simply an older battery that no longer holds sufficient charge. Whatever the cause, you can use jumper cables to connect your dead battery to a live vehicle battery of the same size. The live battery then charges your dead battery enough to get the car started again.
- Park the donor vehicle (live battery) next to the vehicle with the dead battery. Position the vehicles so that the batteries are as close together as possible, but make sure the two cars do not touch.
- Switch off the radio, headlights, interior lights, and — if safe — emergency flashers on both vehicles.
- Turn both vehicles off. Set the parking brakes, and switch each car into park or neutral (for automatic or manual transmissions, respectively).
- Identify the positive and negative battery terminals. The cables leading to the positive battery terminal are almost always red. If you're in doubt, the battery itself has a "+" and "-" sign to mark the positive and negative terminals.
- Check the terminals on the battery for corrosion before jump starting. If you notice any corrosion on the terminals, clean them and then try to start the car once more before proceeding with the jump. The battery may not be dead it just may have a bad connection.
- Separate the jumper cable clamps so that there's no risk of them accidentally touching together — this could cause a short circuit.
- Leads on jumper cables are normally not the exact same length to prevent them from touching. If they are the same length, make sure they have not been modified in any way or damaged.
- Clamp one of the red clamps securely onto the positive terminal of the dead battery. Make sure the clamp is securely attached to the battery terminal.
- On some vehicles, you may have to remove a plastic cover from the positive battery terminal before you can make this connection.
- Secure the other red clamp to the positive terminal on the donor battery. Again, make sure the clamp is securely connected and won't slip off due to vibration in the engine compartment.
- Connect one of the black jumper-cable clamps to the negative terminal on the donor battery.
- Ground the last clamp. Attach the other black clamp to an unpainted metal surface inside the engine compartment on the vehicle with the dead battery — the farther from the battery, the better.
- An unpainted bolt on the engine block is ideal. Remember, the clamp must be able to "bite" securely onto the object in question and hold in place, even if the engine vibrates.
- You can, theoretically, connect the second black clamp to the negative terminal on the dead battery instead. But this produces a spark, which could ignite hydrogen fumes from the battery.
- Check to make sure no part of the jumper cables — or tools, or battery covers — dangle into the engine compartment, where it might foul belts, pulleys, or other moving parts.
- Start the donor vehicle and let it idle for a few minutes before you attempt to start the car with the dead battery. Run the RPM up to about 3,000 as you attempt to start the car with the dead battery.
- Disconnect the jumper cables in the following order once you get the dead-battery car running:
- Negative ground (engine-block bolt or, less desirably, negative terminal on the dead battery).
- Negative terminal (black clamp) on the donor battery.
- Positive terminal on the donor battery.
- Positive terminal on the previously dead battery.
- Don't turn off the car you just jump-started until you're in a safe location or have another jump start handy; depending on the condition of your battery and your alternator, which charges the battery, you might need to jump-start the car again.
- Leave the recently jumped car on for at least 15 minutes to let the alternator charge the battery.
- Some vehicles have a plastic cover over the entire battery that you must remove before you can jump start the car or use it to jump start another vehicle. The cover usually comes off easily with hand-turn screws or a basic screwdriver. Check under your hood before it becomes an issue to be sure whether you need to keep a screwdriver or other tool in the car, just in case.
- Some cars have batteries under the rear seat or in the trunk of the car, but they will allays have a jump port under the hood. It will be marked with a red plastic cover with a plus sign on it.
- Always jump-start a 12-volt battery from another 12-volt battery; using a stronger battery could damage your car's electronics.
- Car batteries discharge hydrogen gas; if there's enough gas, a stray spark could ignite it. Connecting jumper cables in the proper order and connecting the negative cable on the recipient battery to the engine block, instead of the battery itself, both reduce the risk of sparks and thus explosion.
- Never jump-start a frozen battery; it might explode. If the battery's sides bulge, it's likely frozen. Some batteries also have an indicator to show whether the liquid inside has frozen or not.