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Is Jump-Starting Your Car Bad for Its Battery? Find Out Here

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In the good old days, you could hit your car with a lump hammer, and it would splutter into life.

However, modern cars have very complex electronic systems. It’s easy to damage them if you don’t treat them right. Technicians even plug the vehicle into a computer to run diagnostics when something goes wrong. 

One common question is if jump-starting your car is bad for its battery? The short answer is yes if you do it incorrectly. It can be done safely, but it’s essential to follow the correct steps and be prepared. If you have any doubts, you should take your vehicle to a respected dealership. 

Check out our guide to jump-starting your car below. 

High Risk

It’s important to understand that jump-starting a modern car is very risky. When they have a technical issue, mechanics plug them into a computer and run a diagnostic. These systems are very advanced and vulnerable to sudden surges. 

Think about everything that depends on electronics in your vehicle. We’re talking about everything like cruise control, Bluetooth, the windows, right down to the locking mechanism. Meanwhile, engine control units ensure that everything is functioning normally. 

If you jump-start your car incorrectly, you can seriously damage these computer systems. This will be extremely expensive to repair. In some cases, it may even be cheaper to write the vehicle off than to repair it. 

Jump-Starting Your Car

It can be safe to jump-start your vehicle if you do everything correctly. 12-volt batteries won’t ruin a car’s electronic systems unless you do something wrong. Usually, the main cause of expensive damage is failing to connect the jump leads correctly to both vehicles. You must do it correctly so that the dead battery charges smoothly. 

Remember that a battery cannot be too dead to jump-start. If it doesn’t charge, you have either connected the jump cables wrong, or there is something else wrong. 

How to Connect Jumper Cables

The other good news is that it’s almost impossible to electrocute yourself when connecting jumper cables. However, you may experience a mild electric shock if you do it wrong. 

Follow these steps to safely connect your jump leads to a battery –


  • Attach the red-handled positive clamp to the positive terminal on the flat battery. 


  • Fix the black-handled clamp to a metal fitting inside the dead car’s engine. 


  • Attach the black-handled negative clamp to the negative terminal on the live battery. 


  • Now you’re ready to jump-start your car!

Jump Start Method 1

After connecting the cable, there are two ways to jump-start a car. The first takes longer, but it’s much safer, with less chance of extensive damage. 


  1. Make sure both cars are turned off. 
  2. Connect the dead battery to a live battery in another vehicle.
  3. Then, when the former is sufficiently charged, disconnect the jump leads.
  4. Crank the car with a flat battery. If the jump-start worked, it should start. 
  5. Allow the car to run for at least 30 minutes to keep the battery active. 

Jump Start Method 2

There is another riskier method that places a heavier load on the battery. 

  1. Repeat the first two steps as method 1. 
  2. However, this time crank the car with the bad battery while the two vehicles are still connected and the other is running. 
  3. This creates a much stronger surge of energy, but it may result in a load dump and electrical problems. 
  4. If the jumper cables heat up, turn the engines off and allow them to cool for a few minutes. 

Protect Your Battery

The best way to avoid jump-starting your car is to take care of your battery. Bear in mind the following tips –

Why is it Flat? 

If your battery is flat, you should ask why? Most cars can sit inactive for at least three weeks before it goes flat. If it’s happening more regularly than this, there must be another problem. 

Don’t Let it Run Down

Avoid running the battery down multiple times because this will result in more problems.

First, there is the toll it takes on the battery itself. Then, there is the increased risk of reversing polarity. This is what damages electronics like the alternator and can be extremely expensive to repair. Keep your battery charged. If the battery keeps dying, there is a problem with the charging system, and you should consult a technician. 

Replace Old Batteries

If your battery is more than four years old, it’s time to think about getting a replacement. They can crack over time.  A new battery is a lot cheaper than trying to repair your car’s electronics. You can even clean your battery with baking soda to ensure that it doesn’t suffer corrosion.

Look after your battery, and it will take care of you. 

Jump-Starting Safety Advice

Never jump-start a damaged battery. If you see physical anomalies or smell sulfur, the battery may be broken. Another sign is if the vehicle fails to restart after a short rest period. 

Don’t use cheap jumper leads because these increase the risk of damage. If your jumper cable is sparking, disconnect them immediately. There is a small chance of the battery exploding and violently releasing acid. 

Higher-quality jump leads have spike protection. Follow the manufacturer’s connecting sequence. Always connect your jump leads the correct way. Otherwise, it won’t work properly, and you risk potential damage. Never smoke when you’re doing a jump-start. Batteries are highly volatile and flammable. 

Avoid letting the cables dangle from the car because they can become entangled. 

Final Thoughts

It’s never ideal to jump-start your car’s dead battery. 

Ideally, you should call a mechanic and arrange for them to take your vehicle away for repairs. However, if this isn’t possible, you can do a jump-start if you know what you’re doing. Don’t take any risks, especially if you’re in an expensive vehicle. Being stuck in your garage or a car park is very frustrating, but it’s only short-term pain. 

Prepare yourself for the worst by investing in high-quality jump cables. If you must do it, you will want to use the best tools possible. 


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