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This Is How to Safely Disconnect Your Car or Truck Battery

This Is How to Safely Disconnect Your Car or Truck Battery

Are you preparing to work on your car or truck? Maybe your battery needs replacing, or you need to remove it for storage. Whatever the reason, it’s essential to know how to disconnect your car battery safely. Car batteries can pose severe safety risks, such as burns, acids, toxic materials, hazardous gases, and even explosions.

In this article, we take a deep dive into car batteries, including how to disconnect your car battery, which terminal you should disconnect first, and how to hook it back up. Let’s begin!

car battery terminal

What Is a Car Battery? 

A car battery is often an overlooked part of the vehicle, but it’s essential. Car batteries typically use lead-acid technology, and they power everything from the starting system to the lights, stereo, and GPS when the car is off. They provide the initial energy your car needs to turn over the engine, and then they offer a steady stabilizing voltage that keeps your engine running.

Your car wouldn’t be able to start or run without this powerful little box, and educating yourself on its components will not only help keep you safe but it will extend your car’s battery life. 

Mechanic removing car battery
When disconnecting your car battery, it is essential to remove the negative side first.

Dangers of Car Batteries?

While your car battery may seem unassuming, it’s crucial to practice caution when disconnecting and working on it. Car batteries can pose significant dangers if you do not handle them correctly. They can produce very high currents of electricity and manufacturers make them with toxic chemicals such as lead and sulphuric acid, which can cause severe burns, loss of eyesight, or even damage to your lungs if you inhale it. 

Moreover, it’s possible to accidentally cause a short when working with a wrench or another conductive tool. A short has the potential to cause severe burns, melt metal, create arcing, or even cause an explosion. Shorting out a car battery has enough energy to even weld metals together!

shorting batteries in parallel

Car batteries can also produce hazardous gasses, especially when charging. The hydrogen and oxygen produced during the recharging process can potentially escape through the vents and cause an explosion.

These batteries also contain lead that can leak out in the acid and fumes. Lead is highly toxic, and while its effects are not immediatly noticable, its know to damage brain tissue and can lead to lessen mental capacity and early onset dementia.

The bottom line is: wear personal protective equipment and always work in ventalated areas with batteries. Understand how to work with your battery safely, and when in doubt, ask a professional. 

Heavy Dangerous Battery
Car batteries are essential parts of your RV, but can be dangerous when not cared for correctly!

Which Battery Terminal Must Be Disconnected First and Why?

Let’s talk about how to disconnect your car battery safely. Remember to always disconnect the negative side first. Doing this will significantly decrease the odds of experiencing a short through the frame of your car or other conductive metals. This is because if you accidentally contact the frame of the car with your wrench when disconnecting the negative nothing will happen. Once disconnected the positive will not pose a short risk to the frame either.

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! By disconnecting the negative first, there’s no short potential to the frame.

car battery shorted out explosion
This was a car battery that was shorted out and exploded! Luckily it was in a bulldozer with a heavy battery box that protected the driver.

Pro Tip: Having an issue with your RV battery? We uncovered Why Your RV Battery Keep Dying?

Do I Need To Disconnect Both Battery Terminals?

By disconnecting both battery terminals, you eliminate the potential for the battery to receive or discharge power. However, to be extra cautious, we recommend going a step further and wrapping the terminals in electrical tape or another nonconductive material. This is especially important if you don’t reinstall the battery right away. You never know who might stumble on an unattended battery!

battery corrosion
Acids and gasses from batteries are very highly corrosive and dangerous to your health.

What Happens If You Disconnect The Positive Terminal First? 

Technically, nothing will happen if you disconnect the positive terminal of your car battery first. However, if you short it out, a lot will happen. Depending on what you short the battery with, you might see sparks, be burned by conductive material, or even experience a battery explosion.

Pro Tip: Bought a new RV? This is the First RV Electrical Upgrade You Should Make: The RV Battery Monitor.

Woman reconnecting car battery
When reconnecting your battery, connect the positive terminal first.

Which Terminal Should You Connect First? 

When reconnecting your battery, always remember to connect the positive terminal first. This is due to the same reason as above: to reduce the chances of shorting your battery. By reconnecting the positive terminal first, there’s no potential for the battery to send an electrical current through the frame or anything else. Always remember: Disconnect the negative first, and reconnect the positive first.

How to Disconnect a Car Battery

How Long Will a Battery Stay Charged If Disconnected? 

If you completely disconnect your car battery and keep it in a secure place, you can expect it to last around six months without a power source. This is much longer than if you keep your battery hooked up to a sitting car because there won’t be any small power draws such as a radio or clock. It’s best to charge your battery every three months to maintain optimal battery health. Just because a car battery isn’t experiencing any power draws doesn’t mean it should sit forever. 

We recommend using a battery tender if letting your vehicle sit for long periods of time.

Battery Tender Plus 12V Battery Charger and...
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Be Careful Around Car Batteries

While most people think a shock is the most dangerous thing about a car battery this is not true. In fact, the voltage of a car battery is so low it cannot shock you and is touch-safe. However, this does not mean they are safe! Wear eye protection and gloves and never short out a car battery and you should be safe when working with them.

Do you have any questions about how to disconnect your car battery? Drop them in the comments below!

Car battery dangers

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Tom & Caitlin Morton of Mortons on the Move gave up the stationary life for one where they are constantly on the move. They are full-time travelers, television hosts, and digital media producers.
They left their jobs, sold their house and possessions, and hit the road in September 2015 in their full-time “home on wheels”. Since then they have traveled the US, Canada, and even internationally by RV.
Now, they are Discovery Channel & PBS TV Co-stars of The RVers, producers of “Go North” on Amazon Prime, co-founders and instructors of RV Masterclass, and contributing authors for and an Arizona travel guide.

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