Whether you need to jump start the car or it’s time to replace a battery, you must know the proper way to disconnect and reconnect the cables. Which battery cable should be removed first but installed last? If you don’t get the answer right, you could put yourself in danger.
In this guide, we look closer at the reasons to take the negative cable off first. We also help you identify the two battery cables and describe in-depth why this step is essential.
Identifying Battery Cables
The battery terminals in your car should be either marked or color-coded. If the terminals are marked, you will see a positive symbol on the positive terminal and a minus sign where the negative terminal is.
There’s also the chance that the caps are color-coded. In this case, red indicates a positive terminal, while the black cap shows you where the negative terminal is. If you are really lucky, your car will include symbols and colors, making it easier to identify.
The negative cable should always be removed first and reconnected last. If you take the positive off first, you could create an electrical short, and there are risks for sparks, especially if anything metal touches the area. You must take proper battery precautions to keep everyone safe.
To disconnect the battery cable, you will need a socket wrench, typically 10mm. It needs to fit on the connector bolt. Turn your wrench counter-clockwise and it should loosen. Just make sure the socket never touches both of the terminals at the same time, or you will create an electrical pathway.
When you remove the negative cable, you want to put it aside. Don’t let it touch the battery or positive terminal.
RELATED: 6 Symptoms of a Bad Ground Strap (Negative Battery Cable)
Which Battery Cable Should Be Reconnected Last?
The negative battery cable should be reconnected last and the positive cable first. When you are putting a new battery in or have finished jump starting it, you have to be careful to reconnect it appropriately. If you follow the steps you took to remove the terminals, you would simply do everything in reverse order.
With these guidelines in place, you must connect the positive terminal first. Once that is complete, you are ready to connect the negative terminal last.
RELATED: Battery Terminal Corrosion Causes (How to Fix & Prevent It)
Why Disconnect Negative First?
If you fail to remove the negative connection from the battery first, you put yourself at risk of an electrical short. As an example, if you were to drop a metal tool on the positive terminal and it also touches anything metal on the vehicle, you could create a circuit.
This problem will short your battery. It can also give you one heck of a shock. That’s why the negative cable should always be the first off and last back on.
However, it’s also just as important that the connectors don’t touch each other or anything else while you have them disconnected. Some people choose to use a plastic zip tie or another item to attach them temporarily somewhere out of the way. Just make sure you don’t let them touch anything made from metal.
Once you are ready to reinstall the connectors, you can remove them from the zip ties. Remember to install the positive cable first and always end with the negative. Give both connectors a strong wiggle to ensure that they are properly seated for the best connection.
Don’t be alarmed if you see a small spark when you put the negative cable back on. This just indicates that you re-established the electrical circuit.
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- Posted on
- in Car Maintenance
- on October 7, 2013
Improperly connecting a car battery cable when jump starting your car can cause serious damage to your car, the car supplying the jump and possibly cause severe injuries from burns to you and the helpful motorist supplying the jump. The charge and discharge cycle of a battery causes hydrogen gases to build up. These gases escape through vented cell caps and can accumulate around the battery. If you connect the jumper cables incorrectly, you can create a much large spark than normal and this spark can ignite these gases and cause an explosion.
1. Connect Positive Cables First
Connect one positive or red cable end to the positive or red terminal on the dead battery. Connect the other end to the positive terminal on the good battery.
2. Connect Good Negative
Attach the negative or black clamp to the negative terminal on the supply battery.
3. Start the Supply Engine
With both positive cables connected and the negative connected to the good battery, start the supply car’s engine.
4. Connect Negative Cable to Ground
Find a clean metal component under the hood on the car being jump started and connect the negative cable end to it.
5. Start the Car
Allow the dead battery to charge for a minute or two and then attempt to start it. If it doesn’t start right away, allow the supply battery to charge the dead one for at least five minutes and attempt to start it again.
6. Disconnect Immediately
Once the car being jumped is running, disconnect both negative cables and then both positive cables immediately. Allowing the jumper cables to remain connected can cause problems with the ignition modules and computers on both cars.
Before you attempt to jump start your dead battery, make sure both terminals on both batteries are clean, otherwise optimum electrical transfer won’t be able to happen.
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