Did you know that there’s a specific order that you need to follow when disconnecting your battery terminals?
Doing it wrong can lead to fatal accidents, electrical damage, and reduced battery performance.
Read more about how to disconnect a car battery correctly to prevent damage and some mistakes to avoid.
This Article Contains:
How to Disconnect a Car Battery (Step-by-Step)
Disconnecting your car battery is a relatively simple process.
It involves these five steps:
- Turn off the ignition and locate the battery
- Disconnect the negative terminal first
- Disconnect the positive terminal
- Detach the holding mechanism and remove the battery
- Clean the battery tray and cable connector
Before you proceed, ensure you have the necessary battery removal tools and understand the safety measures.
Tools Needed
Your vehicle’s battery terminal bolts aren’t a standard size — they can be a single bolt, clamp, or bolt and nut pair. It’s best to have a socket wrench kit and an adjustable wrench (pliers) to deal with bolts of different sizes and forms.
You may also want some anti-corrosion grease or rust spray on hand.
Safety Measures
Here are some precautions to keep you and your car safe:
- Batteries contain chemicals that produce flammable gas. Work in an open environment to minimize the possibility of gas buildup and exposure.
- Ensure the workspace is dry since a car battery holds an electric charge, and you could risk an electric shock channeled through wet surfaces.
- Metal is conductive, so remove any jewelry to minimize the risk of an electric shock from accidental contact with a battery terminal.
- Wear safety glasses (safety goggles) and gloves to reduce the likelihood of accidents or injuries.
- Keep the driver’s door open, as some cars can lock themselves when the battery is disconnected.
- If you drive an automatic car, ensure it’s in “Park.” However, if it’s a manual car, ensure it’s in first gear to prevent it from rolling.
It’s a good idea to check your owner’s manual to see what electronics will be affected by the loss of battery power.
Once you’ve taken care of that, you can start disconnecting your battery by following these steps:
Step 1: Turn Off the Ignition and Locate the Battery
Turn off the car’s ignition switch and remove the key. Then, locate your car battery.
Most of the time, it’ll be in the engine bay. However, in some modern cars, batteries are located in the trunk or under the rear seat — making them a little harder to access. Refer to your owner’s manual if you can’t find it.
Once you’ve located the battery, check it for corrosion, damage, or leakage.
If a car battery terminal is heavily corroded, disconnecting the battery clamp or connector from the battery post may be more challenging. Don’t try to force the connector off, as you could break the battery post.
In this case, you’ll need to loosen some of the corrosion first. You can use a solution of water mixed with baking soda and a wire brush to remove the corrosion.
Note: If the car battery is damaged, bloated, or leaking, don’t work on it. Instead, call a mechanic, as you’ll likely have to replace it.
Step 2: Disconnect the Negative Battery Terminal First
You can find the positive and negative battery terminals on top of the battery. Some battery terminals are covered with plastic caps that need to be removed.
The negative battery terminal is usually marked with a minus (-) symbol and has a black cap, whereas the positive terminal typically has a plus (+) symbol and a red cap.
When disconnecting a car battery, always remove the negative connector (negative battery clamp) from the negative terminal first. This helps to avoid electric issues like sparks and shocks and, in some cases, battery explosions.
How do you disconnect it?
Gauge the size of the socket wrench you’ll need (usually 8,10, or 14 mm), fit it over the connector bolt, and turn left (counterclockwise) to loosen.
Important: Don’t let your adjustable wrench touch both terminals simultaneously, as you’ll create an electrical path. Once the negative connector and negative cable have been released, remove them and keep them away from the battery and positive terminal.
Step 3: Disconnect the Positive Terminal
After the negative car battery terminal is disconnected, do the same for the positive terminal. Loosen the positive connector and positive cable with the pliers, then keep them away from the battery and negative cable.
Don’t let the positive connector touch any metal part of your car, as it can carry a residual current that may damage or disrupt the vehicle circuit.
Step 4: Detach the Holding Mechanism and Remove the Battery
Most batteries are secured to the battery tray with a battery hold-down mechanism. This is usually a bracket or strap.
Find the holding bolts and loosen them to detach the battery hold-down mechanism. Some bolts are close to the base of the tray, and you may need to reach further down with the socket wrench.
Be careful when lifting the battery off the tray as it can be surprisingly heavy, often weighing between 30-60 lbs.
Caution: When removing a flooded lead-acid battery, lift it straight up to avoid sloshing the battery acid inside and place the old battery on a level surface.
Step 5: Clean the Battery Tray and Battery Cable Connector
Once battery removal is complete, you’ll want to clean the battery tray and cable clamp or connector for future use. Do this irrespective of whether you’re installing a new car battery or just taking the car battery out for a recharge.
Clean the battery tray and connectors of any dirt and corrosion, then spray it with an anti-corrosion compound or rust spray.
Always ensure the positive and negative battery cable is secured out of the way. Don’t leave them hanging loose from your engine bay.
What’s next?
If you plan to install a new battery or put back the current one, reverse the entire process:
- Secure the new battery with the holding mechanism before reconnecting the terminals.
- Apply some anti-corrosion grease on each battery terminal and connector.
- When reconnecting the car battery, first connect the positive cable, followed by the negative battery cable.
Note: Disconnecting and reconnecting a car battery is easy if you follow due process and wear safety goggles. However, it’s best to let a professional handle it if you have doubts.
Still have some questions?
Read more about car batteries in the following FAQs.
5 FAQs About Car Batteries
Here are answers to some common car battery questions:
1. When Would I Need to Disconnect the Car Battery?
You may have to disconnect the car’s battery from the engine bay in several situations:
- Replacing a faulty battery is one of the most common situations in which you must disconnect the main battery. Ensure you dispose of the old battery properly.
- You may not have to remove the main battery from the engine bay when recharging a battery. However, you do need to disconnect the cables and hook the battery to a battery charger.
Note: If you’re uncertain about recharging a battery, ask a mechanic to do it. They can also test and diagnose the cause of the battery drain. - It’s a good idea to remove the main battery from the engine compartment while cleaning corroded battery terminals. This prevents corrosive elements and cleaning agents from falling on engine parts.
- Some car maintenance procedures may require disconnecting or removing the battery to prevent short circuits while accessing engine parts.
- If you plan on storing a vehicle for an extended period, it’s advisable to disconnect at least the negative terminal from your car battery. Doing this prevents unnecessary battery drain, as a fully charged battery can hold its charge for 6 to 12 months.
You can also attach the battery to a trickle charger or battery tender to help maintain its charge. Using a trickle charger ensures your battery is up and running when you need to re-use it.
2. What’s a Lead-Acid Battery?
The lead-acid battery is a commonly found battery type in modern cars. It can be in a wet cell (flooded) or a dry cell (gel or AGM) format. The battery generally consists of lead plates and battery acid (water and sulfuric acid).
However, there are many different types of car batteries apart from lead-acid batteries.
3. What Does a Car Battery Do?
The primary battery function in the car is powering the starter to crank the engine. The car battery also provides power for every electrical component in your car — from the headlights to the onboard computer.
When your car is running, the alternator recharges the battery.
However, your battery may sometimes rely on its stored charge when the engine is off. This is why avoiding unnecessary drain from the electrical system (like the headlights) is essential when it’s not running.
4. Can I Recharge a Dead Battery?
Successfully recharging a dead battery depends on how depleted the battery is.
You’ll need a voltmeter or multimeter handy to measure your battery voltage and know its state of charge. If the battery voltage is 12-12.4 volts, it still has about 25-75% of its charge, but not enough to start the car.
In this case, you can jump-start the car and drive it for at least a 30-minutes to let the alternator recharge the battery. However, avoid using electronics and keep the car above idle as much as possible.
If the voltage is under 12 volts, the battery is fully discharged. You can still jump-start the car, but charging with the alternator isn’t advisable when the car battery is this depleted.
Instead, use a dedicated battery charger to recharge a depleted car battery. But remember that a very old battery could be unrecoverable and may not charge.
5. What Mistakes Can I Avoid When Replacing My Car Battery?
Here are three crucial mistakes every car owner should avoid when replacing a car battery:
A. Waiting Too Long
Delaying car battery replacements can result in vehicle breakdowns or severe accidents. It’s a good idea to replace your car battery promptly.
B. Using the Incorrect Battery
Ensure using the correct battery by reading some car reviews and learning about basic battery specifications for your particular vehicle, such as:
- Battery type: Select the appropriate type of battery for your vehicle.
- Battery size: Determine if the battery will fit into your car.
- Terminal placement: Ensure the battery will connect to your car’s electrical system.
C. Going for the Cheapest Option
Most car insurance plans don’t cover battery replacement costs, but this doesn’t mean you should choose the cheapest option. A cheap battery may not adequately power every electrical component of your car or last as long as desired.
Instead, as a car owner, consider investing in one that offers improved specifications, features, and lifespan.
Get Prompt Battery Repairs with AutoNation Mobile Service
Disconnecting a vehicle battery isn’t a difficult task. The important thing to remember is that the negative terminal comes off first. And when you’re reconnecting it, reverse the sequence.
However, if you have other battery issues requiring battery replacement and you want to be extra safe, try AutoNation Mobile Service.
We’re a mobile auto repair and car maintenance service offering convenient online booking, upfront pricing, and a 12-month | 12,000-mile repair warranty. To get an accurate price estimate for battery replacement service, fill out this online form with your car specifications and personal information.