We’ve all been there – a dead car battery with no one around to help. Desperate to get your car running again, you retrieve the jumper cables from your emergency kit or find a good Samaritan who has a set and you quickly get to work.
In the heat of the moment, however, it’s all too easy to make a mistake and connect the cables the wrong way. But what exactly happens if you do make that blunder?
Connecting jumper cables incorrectly can lead to a host of problems. Polarity reversal is no joke, as it can cause electrical current to flow in the wrong direction, wreaking havoc on your car’s electronics and even posing a risk of sparking a fire. Let’s go over exactly what can go wrong including the absolute worst-case scenario.
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The CORRECT Way to Connect Jumper Cables
When it comes to jumping a car battery, using jumper cables correctly is the most important thing. Knowing how the cables work and how to connect them properly can save you from potential damage to your vehicle or even injury.
There are two jumper cables, each with a different color: red and black. The red cable is used to connect the positive (+) terminals of both the dead and the booster batteries, whereas the black cable connects the negative (-) terminals.
To ensure a successful jump, follow these steps.
1. Park Vehicles Close to Each Other
Make sure the batteries are near each other, but do not let the vehicles touch. In most cases, this will be with the front of each car facing each other. This positioning will make connecting the jumper cables much easier, especially when the cables have shorter lengths.
While most car manufacturers place the car battery in the front of the vehicle under the hood, some, like BMW and Mercedes Benz, may put it towards the rear of the vehicle such as the trunk or even under the rear seat. In these cases, you may need to park in a different way so the cables will reach each battery.
2. Turn Off Both Vehicles
Before connecting the jumper cables, ensure both vehicles are switched off. This is crucial for safely jump-starting a car and avoiding any damage.
3. Identify the Battery Terminals
Locate the battery in each car, and make note of the positive (usually marked by a plus sign or red color) and negative (usually marked by a minus sign or black color) terminals.
4. Connect the Positive Terminals
Take the positive (red) jumper cable and attach one end to the positive terminal of the donor battery. Then, connect the other end to the positive terminal of the dead battery.
5. Connect the Negative Terminal on the Donor Battery
Attach one end of the negative (black) jumper cable to the negative terminal of the donor battery.
6. Connect the Negative Terminal on a Metal Grounded Surface
Instead of connecting directly to the negative terminal of the dead battery, attach the other end of the negative jumper cable to a clean metal surface on the vehicle with the dead battery. This acts as a ground and helps prevent sparks during the process.
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What Happens If You Connect Jumper Cables Wrong?
Potential Damage Caused
Let’s say you’re jump-starting your car, and you accidentally connect the jumper cables the wrong way. Normally, you’re going to see some sparks and may even feel a surge of electrical current. This is because the reverse polarity causes the current to flow in the opposite direction, which can lead to damage or even personal injury.
Connecting the cables backwards can also damage the vehicle’s electrical system and the battery itself. As a result, you might experience malfunctions in different components or a dead battery that won’t take a charge.
Effects on the Vehicle’s Electrical System
When you jump a car the wrong way, various parts of the electrical system may suffer. This includes the fuse box, which might blow a fuse or two due to the improper flow of electricity. You’ll want to check the fuses and replace any that are broken to restore proper functionality to the affected parts of your car.
In more severe cases, the reversed jumper cables can fry the vehicle’s fusible links or starter relay. These components protect the car’s circuits, so replacing them will be necessary to get your car back in working order.
While all this information might sound scary, modern vehicles often have built-in safeguards to prevent significant damage. Nevertheless, you’ll always want to double-check the connections before jumping your car to avoid any potential mishaps.
Assessing and Troubleshooting the Damage
Let’s assume for a second that you accidentally connected the jumper cables the wrong way. What now?!? There are a few things you can do to assess and troubleshoot the damage done to your car’s electrical system.
First, double-check your owner’s manual to locate the fuse box or panel in your vehicle. You might find that the issue is just a blown fuse, which is easy to replace. Inspect all the fuses and swap out any damaged ones with new ones. Make sure the replacement fuses have the same amperage rating as the blown ones.
Even if you didn’t notice any immediate signs of damage, it’s a good idea to check the battery itself. Get a multimeter and test the voltage of your battery while the engine is off. A healthy battery should read between 12.6 and 12.8 volts. If it’s lower than that, you might need a new battery or further troubleshooting.
Keep an eye out for electrical components acting strange. This could include dimming lights, issues with power windows, or unusual behavior in your car’s audio system. Make a list of all the electrical malfunctions you encounter to help a mechanic pinpoint the issue if needed.
Now, even if you feel confident in your troubleshooting abilities, it’s recommended to bring your car to a trusted mechanic to inspect for any other potential issues. As many have found out, automotive electrical issues are often some of the most difficult to troubleshoot. The pros will have the expertise and tools needed to find any hidden damage that you may have missed.
Remember… accidents happen. You’re not the first person to hook up jumper cables the wrong way and you won’t be that last.
Can You Get Electrocuted by a Car Battery?
Fortunately, no. You cannot be electrocuted by a car battery. Car batteries typically provide 12 volts of electrical power, which is simply not enough voltage to cause electrocution.
However, it’s still important to always use caution and follow proper safety guidelines when working around batteries.
One key danger associated with older car batteries is the potential for an explosion. While highly unlikely (and actually impossible with many modern car batteries), this can occur due to a phenomenon called “gassing,” where the battery releases flammable hydrogen gas. If the hydrogen gas is ignited by a spark, like those that can happen with incorrectly connected jumper cables, the entire battery can explode, potentially showering you with sulfuric acid.
While connecting jumper cables the wrong way might not result in electrocution, it can still cause damage to both vehicles involved. Always use caution and adhere to safe practices when handling car batteries or using jumper cables.
What’s the Absolute Worst Case Scenario?
If you’re the type of person that often wonders, “what’s the worst that could happen?”, this section is for you.
If you hook up jumper cables the wrong way, luck actually plays a big part as well as a vehicle’s electrical system.
- BEST CASE: Nothing happens
- ALMOST BEST CASE: Blown fuse or two
- WORST CASE: Electrical component(s) short out, ECM is fried, car won’t run, expensive repairs in your future
- EXTREME WORST CASE: Battery blows up in your face (highly unlikely) and fire