How to change a car battery – all you need to know

If you have ever turned the ignition or tried to start your vehicle and been greeted by silence, then you may need to change the battery.

Starting problems are often caused by a flat or dead car battery. Thankfully, replacing a faulty battery is a simple task. And you can do it yourself or use the RAC battery fitting service.

If you want to change your car's battery yourself then this step-by-step car maintenance guide will show you what you need to do to get back on the road.

Are you experiencing a car fault, warning, or mechanical problem on your road trip? Find a local mechanic with the RAC.

How to change a car battery 

• Switch off the vehicle
• Open the bonnet and locate the 12v battery
• Identify the positive (+, usually red) and negative (−, usually black) terminals
• Disconnect negative terminal first
• Disconnect positive terminal
• Remove any securing bracket or clamp holding the battery in place
• Lift out the old battery
• Place the new battery in the tray in the same orientation
• Secure new battery with the bracket/clamp
• Reconnect terminals in reverse order meaning positive first and then the negative
• Tighten connections and close the bonnet
• Start the car to check it’s working

Before you start

Before changing a car battery, you will need to correct tools and safety equipment.

This includes:

• Spanner or socket wrench to loosen up the connections
• Wire brush to remove corrosion and dirt
• Microfiber cloth to clean and dry the area

When it comes to safety equipment, protective gloves are important as batteries have highly acidic and harmful liquids. You should also use safety glasses or gobbles to protect your eyes from fluids, sparks and other debris.

Changing a car battery – a step-by-step guide

Here are the steps you need to take to replace a car battery.

How to remove a car battery?

Here, we will tell you how to safely remove a in a few simple steps. However, the first step is to make sure that the engine is off and keys are removed from the engine.

1. Locate the battery:

• Car batteries will be found in the engine compartment. If you are unsure, then your vehicle's owner's manual will have all the information.

2. Disconnect the negative terminal:

• The negative terminal is usually marked with a "-" symbol or labelled "Neg".
• Loosen the nut or bolt that secures the negative cable to the terminal using a spanner or pliers.
• Once the nut or bolt is loose, gently twist and pull the cable away from the terminal. Do not to touch any metal parts with the cable.

3. Disconnect the positive terminal:

• The positive terminal is usually marked with a "+" symbol or labelled "Pos".
• Follow the same steps as above.

4. Remove the battery hold-down bracket:

• Some car batteries have a hold-down bracket. Remove these are they are holding the battery in position.

5. Lift out the battery:

• Carefully lift the battery out of the battery tray, taking care not to tip it or spill any acid.

6. Clean the battery tray:

• Before installing a new battery, clean the battery tray and remove any corrosion or residue. Rinse with clean water and dry thoroughly.

How to reconnect and install a car battery

When installing a new battery or reconnecting the old one, reverse the steps from above and connect the positive terminal first, followed by the negative terminal.

To reconnect a car battery, position the new battery in the engine battery tray; re-connect the positive terminal; connect the negative terminal; check the connections; and then start the engine.

Preparation

Park the car on level ground, switch off the engine, and open the bonnet. Locate the battery and gather essential tools such as gloves, eye protection, and the correct tools. Identify the positive and negative terminals, check for any covers or brackets, and ensure the area is safe and stable before beginning the removal process.

Removing battery

Start by disconnecting the negative terminal first to prevent electrical shorts, then remove the positive terminal. Move both cables aside so they cannot touch the battery. Undo any retaining clamps or brackets securing the battery. Lift the battery out carefully, keeping it upright to avoid spills. Inspect the tray for corrosion or debris before installing the new unit.

Installing battery

Place the new battery into the tray in the same orientation and secure it with the clamp or bracket. Reconnect the positive terminal first, followed by the negative, ensuring both are tightened firmly. Check that the battery is stable and connections are solid. Start the engine to confirm proper operation, then recycle the old battery responsibly.

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What is a car battery?

A car battery is a rechargeable power source that supplies electricity to a vehicle’s systems. Usually located in the engine bay, it provides the energy needed to start the engine and supports electrical functions when the engine is off or demand exceeds the alternator’s output.

Designed to deliver high current briefly during start‑up, it also supplies steady power while the engine runs and helps maintain stable voltage for the vehicle’s components, including modern in‑car entertainment systems.

Most car batteries are lead‑acid units containing lead plates and a sulfuric acid electrolyte, which generate electricity through chemical reactions. Standard car batteries are 12‑volt, though larger or more power‑hungry vehicles may use higher‑voltage versions.

How long does a car battery last?

Your car battery can last for many years - however, this can vary for many reasons.

Driving conditions, climate, and maintenance can all have an impact.

The quality of the battery itself and how it was originally installed will also make a difference to the lifespan of the battery.

However, on average, a car battery can last between three to five years.

Signs you have car battery issues

There are certain things that can show that it may be time to change your car battery:

These can include the age of the battery, slow engine cranking, dim headlights, electrical issues, a swollen battery casing, or a build-up of corrosion on battery terminals.

How long does an electric car battery last?

When it comes to electric vehicles (EVs), their lifespan is considerable larger than one in a petrol or diesel car.

This is because they are larger, vastly more expensive to make and built to last for longer periods of time.

Drivers of EVs can expect upwards of 10 years or 100,000 miles of use

However, bear in mind that most EVs also have a traditional 12-volt battery to power the car's on-board equipment, which will have the same lifespan as a petrol or diesel car's battery. 

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How to charge a car battery

There are several ways to recharge your car battery.

• Use a car battery charger
• Use a speed or trickle charger
• If this still isn’t working, then you may need to jump start your car

How long does it take to charge a car battery?

It takes 2 to 8 hours to charge a 12v car battery. In some cases, it can take up to a day to charge.

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How much does a new car battery cost?

A cost of a new 12v car battery starts at around £200 – not including the cost for it to be fitted and tested by a mechanic.

The make, quality and size of the battery all have an impact on the price you pay – as well as how common the battery itself is.

How to dispose of car batteries

Car batteries contain hazardous materials like lead and acid, so they must never be put in household waste, and this is why the safest option is to take the old battery to an approved recycling point where it can be handled correctly.

Many drivers can return them to retailers, garages, or metal recycling centres, all of which typically accept used batteries for proper processing.

However, council recycling centres also provide dedicated drop‑off areas for car batteries.

Recycling prevents toxic substances from entering the environment and allows valuable materials to be recovered and reused, making it both the safest and most responsible way to dispose of a car battery.

What is car battery recycling?

Car battery recycling is a process of collecting, processing, and reusing or disposing of used car batteries in an environmentally responsible manner.

As they contain various components and chemicals that can be harmful to the environment if not properly handled and recycled, it is important to do this correctly.

The recycling of car batteries involves several steps:

1. Collection: Used car batteries are collected from various sources, including automotive service centres, recycling centres, battery retailers, and other designated collection points. It is important to ensure that used batteries are properly stored and transported to prevent leakage or damage.
2. Sorting: Once collected, the batteries are sorted based on their type, size, and chemistry. Lead-acid batteries are the most common type found in cars and are distinguished from other battery types.
3. Drainage: Before recycling, the batteries undergo a process called drainage to remove the remaining electrolyte or sulfuric acid. The acid can be neutralised and treated for safe disposal or used in other industrial processes.
4. Breaking: The drained batteries are broken or crushed to separate the plastic battery casing, lead plates, and other components. This process helps in recycling the individual components more efficiently.
5. Recycling: The separated components, including the plastic, lead, and other metals, undergo further recycling processes. The lead can be melted and purified for reuse in the manufacturing of new batteries or other lead-based products. The plastic is typically recycled into new plastic products, while other metals like steel can also be recycled.
6. Environmental safeguards: During the recycling process, proper environmental safeguards are followed to minimise the release of hazardous materials. For instance, the acid is neutralised and treated, and emissions are controlled to prevent pollution.

By recycling car batteries, valuable materials such as lead and plastic are recovered and reused, reducing the need for mining, and manufacturing new materials.

Moreover, recycling helps to prevent the improper disposal of hazardous battery components, which can contaminate soil and water sources.

It's important to note that car battery recycling should be carried out by certified recycling facilities who adhere to environmental regulations and safety standards.

Are you looking for a new car battery? The RAC has a wide range available.

A mobile mechanic can carry out a vehicle diagnostic check where they can see the current status on your battery.

Flat or dead batteries are one of the most common causes for a breakdown according to RAC data, so using the RAC’s battery fitting service means you can get back on the road as soon as possible.