Once the dead car's engine is running, remove the jumper cables in the opposite order that you put them on: Disconnect the black clamp from the grounded metal section of the dead car. Disconnect the black clamp from the good battery. Disconnect the red clamp from the good battery.
Disconnect the Cables:
Carefully disconnect the cables in the order reverse from their placement in the vehicles. Disconnect the negative cable from your car, then the negative cable from the other car, then the positive cable from your car, and, finally, the positive cable from the other car.
When you reverse the polarity of the jumper cables, you create a drastic increase in the amount of electrical current that runs through them. As a result, the cables may melt or even catch fire.
Step 5: Disconnecting the Jumper Cables
If your car does start, leave it running. Now disconnect the battery cables by first removing the negative clamp from the bare metal connection under your car's hood. Then remove the red clamp from your battery's positive terminal—and do not let the clamps touch.
“Positive first, then negative. When disconnecting the cables from the old battery, disconnect the negative first, then the positive. Connect the new battery in the reverse order, positive then negative.”
Expert Reply: By removing the negative battery cable you are disconnecting the battery from the chassis of your vehicle. If you begin to remove the positive side before the negative and your wrench would make contact with any part of the vehicle, then you could cause a short in the system.
If you disconnect the positive terminal first, one slip of your wrench could send a direct short to the ground, which can be very dangerous. Its possible that you could experience a huge spark, the wrench could melt in your hand or the battery could even explode!
Step 10: Disconnect the black jumper cables first, then disconnect the red ones. Once the dead car is running, you may disconnect the jumper cables, starting with the black, negative cable clamps. Do not let the clamps touch each other while any part of the cables is still attached to a car.
First the clamp of the red cable is connected to the positive terminal of the assisting vehicle. The other end of the red cable is connected to the positive terminal of the broken down vehicle. Then the black clamp is connected to the negative terminal of the assisting battery.
The battery will charge faster if you rev the engine faster. Why? Because the faster the crankshaft turns, the faster it turns the belt that runs the alternator. And the faster the alternator turns, the more electricity it produces to run all the electrical stuff in the car — and recharge the battery.
Never connect the black cable to the negative (–) terminal on your dead battery. This is very dangerous, could result in a possible explosion. Make sure you follow the instructions in your owner's manual when jumpstarting your vehicle.
Connecting the red terminal to the dead battery first would minimize damage if the other red clamp were accidentally dropped so as to contact the frame of that vehicle.
If you have jump-started your car, it is recommended to let your vehicle run for at least 30 minutes because it would typically require at least half an hour to charge a dead battery entirely or at least sufficiently.
Please remember that the jumper wire color is meant to help lessen confusion when making connections. However, the actual color of jumper wires does not matter as long as the connections from pin to pin are correct.
Take up the other end of the jumper cable, making sure these red and black ends don't touch. Going over to the live battery, you'll want to attach the red (positive) lead to the red terminal first. Then, attach the black (negative) lead to the black terminal on the live battery.
Make sure you disconnect the negative terminal first. Lay the disconnected negative cable carefully to one side, making sure it's well away from the battery terminal. Disconnect the cable from the positive battery terminal in the same way, then lay it to one side.
Connecting the negative terminal first can create a short circuit, potentially damaging the battery, and electrical system, or even causing injury. By connecting the positive terminal first and then the negative, you can minimize the risk of any accidents or damage, ensuring a safe and successful installation.
Will the Car Battery Drain if the Negative Cable Is Disconnected? A car battery will self-discharge at a rate of 5-15% per month with the negative terminal disconnected. However, the alternative option of leaving the battery connected while it isn't being used will drain at close to 20% per week.
Connect positive first, negative having less potential won't arc. The higher the voltage, the greater the chance of arcing and fusion. On a car if negative first and you are touching any metal part of car, when attaching positive there is possibility of arcing through you. Your body becomes part of the circuit.
A 12v car battery cannot overcome the resistance in your body. It will not shock you in any way. The reason you connect positive first is because of you connected negative, you'd be completing the circuit by connecting positive.
Once your dead battery is jumpstarted, you should drive around for about 30 minutes. Don't leave your car sitting idle or it won't charge as quickly. After 30 minutes, your car should start again next time and each drive after that will continue to charge it.
It's best to drive the car around or let it idle for at least 30 minutes after you jump-start it. Ideally, you should drive the car around for 30 minutes to allow the alternator to charge the battery to a good level. Even after that if you still have a flat battery, it could be an issue with the alternator.
One common reason why a car won't jump start is because the battery is completely dead. If the battery is completely dead, it won't have enough power to turn over the engine, even with a jump start. In this case, you'll need to replace the battery to get your car running again.
The negative () cable is the ground cable; it is always connected to the frame or body metal and can safely be disconnected first with no chance of causing sparks. By the same token, always reconnect the positive cable before connecting the negative cable.