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

How to change a car battery – all you need to know
The life of car owner can come with many challenges – and unfortunately, many have experienced issues with a car battery.

If you have ever turned the ignition or tried to start the vehicle and been greeted by silence, then you know that there is a problem.

Often it is due to a flat or dead car battery. This guide looks into what you will need to do and how to get back on the road.

What is a car battery?

A car battery is a rechargeable energy storage device that provides electrical power to the various components and systems of a vehicle.

It is typically located in the engine compartment and serves as the primary source of electricity for starting the engine and powering the vehicle's electrical systems when the engine is not running – or when the electrical load exceeds the capacity of the alternator.

Car batteries are designed to deliver high amounts of electrical current for short periods, particularly during engine start-up.

They also provide a steady flow of power to the vehicle's electrical system when the engine is running, and they help stabilise the voltage to ensure proper operation of the vehicle’s various components.

It also helps power entertainment systems that are in many modern cars.

Most car batteries are lead-acid batteries, which consist of a plastic case filled with a sulfuric acid electrolyte solution and lead plates. The chemical reaction between the lead plates and the electrolyte produces electrical energy.

Car batteries are typically 12-volt batteries, however, larger vehicles or those with additional electrical demands may have batteries with higher voltages.

All batteries require recharging, as the chemical reaction that produces electricity depletes the amount of energy over a long period of time.

When driving, the vehicle's alternator recharges the battery while the engine is running by converting mechanical energy from the engine into electrical energy.

Regular car maintenance, such as checking the battery's terminals for corrosion and ensuring proper electrical connections, is important for the longevity and performance of a car battery.

Over time, car batteries can degrade and lose their ability to hold a charge, requiring replacement.

Visiting a local garage or contacting a mobile mechanic are good ways to keep your battery in top condition.

Alternatively, you can keep your car battery in its best shape through the annual service.

The RAC Service and MOT Plan lets drivers spread the cost of routine servicing and MOTs over two years so they don’t have to pay big bills all in one go – with no risk of prices increasing.

How long does a car battery last?

The lifespan of a car battery can vary depending on various factors such as the quality of the battery, driving conditions, climate, and maintenance – as well as the quality of the battery itself and how it was originally installed.

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

It is important to note that this is just a general estimate, and the actual lifespan can be shorter or longer than this and you should check your car owner’s manual for further information.

Signs you have car battery issues

There are certain signs that indicate it may be time to change your car battery:

Age: It's a good idea to consider replacing it, even if it seems to be functioning fine. As batteries age, their performance and ability to hold a charge diminish. Speak to your local garage when having your annual service for a better understanding of its current condition.

Slow engine cranking: If you notice that your engine is slow to start or it takes multiple attempts to start the vehicle, it could be a sign that the battery is weakening and needs to be replaced.

Dim headlights and electrical issues: A weak battery may result in dim headlights, dim interior lights, or other electrical components not functioning properly. If you experience car headlight or electrical issues, it's worth checking the battery's health.

Swollen or bloated battery case: If you notice that the battery case appears swollen or bloated, it indicates a problem with the battery and should be replaced immediately.

Corrosion and build-up on battery terminals: This can affect the battery's performance. Regularly inspect the terminals, and if you notice significant corrosion that cannot be cleaned off, it may be time for a new battery.

It's important to mention that extreme weather conditions, such as excessive heat or cold, can also affect the lifespan of a car battery. In harsh conditions, batteries may wear out more quickly.

Therefore, it's a good idea to monitor your battery's performance regularly and consider replacing it if you notice any signs of deterioration.

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 and built to last for longer periods of time.

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

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

How to remove a car battery?

Here, we will tell you how to safely remove a car battery in a few simple steps.

1. Safety precautions:

  • Make sure the engine is turned off and the keys are removed from the ignition.
  • Wear safety goggles and gloves to protect yourself from any potential acid or electrical contact.

2. Locate the battery:

  • Car batteries are usually located in the engine compartment. Consult your vehicle's owner's manual if you're unsure of its exact location.

3. Disconnect the negative terminal:

  • The negative terminal is usually marked with a "-" symbol or labelled "Neg" or "−".
  • 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. Be careful not to touch any metal parts with the cable.

4. Disconnect the positive terminal:

  • The positive terminal is usually marked with a "+" symbol or labelled "Pos" or "+".
  • Follow the same steps as above, loosening the nut or bolt and removing the positive cable from the terminal.

5. Remove the battery hold-down bracket:

  • Some car batteries have a hold-down bracket that secures the battery in place. Use a spanner or socket to remove any bolts or brackets holding the battery in position.

6. Lift out the battery:

  • Carefully lift the battery out of the battery tray, taking care not to tip it or spill any acid. Car batteries can be heavy, so use proper lifting techniques or ask for assistance if needed.

7. Clean the battery tray:

  • Before installing a new battery, clean the battery tray with a solution of baking soda and water to remove any corrosion or residue. Rinse with clean water and dry thoroughly.
  • The old battery has now been removed. Remember to handle the old battery with care and dispose of it properly at a recycling or automotive store that accepts used batteries.

How to reconnect 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, follow these steps:

1. Position the new battery:

  • Place the new battery into the battery tray, ensuring it is securely seated.

2. Connect the positive terminal:

  • Locate the positive terminal on the battery, marked with a "+" symbol or labelled "Pos" or "+".
  • Take the positive cable (usually red) and align it with the positive terminal.
  • Slide the cable over the terminal and ensure a tight connection.
  • Tighten the nut or bolt on the positive terminal using a spanner or pliers. Make sure it is snug, but avoid overtightening.

3. Connect the negative terminal:

  • Locate the negative terminal on the battery, marked with a "-" symbol or labelled "Neg" or "−".
  • Take the negative cable (usually black) and align it with the negative terminal.
  • Slide the cable over the terminal and ensure a tight connection.
  • Tighten the nut or bolt on the negative terminal using a spanner or pliers. Again, ensure it is snug but avoid overtightening.

4. Check the connections:

  • Once both terminals are securely connected, give them a gentle tug to ensure they are firmly attached to the battery. The cables should not easily come loose.

5. Inspect for corrosion:

  • Take a moment to inspect the battery terminals for any signs of corrosion. If you notice any, it's recommended to clean the terminals before proceeding.

6. Test the connection:

  • With the battery reconnected, you can now test the electrical systems in your car to ensure everything is functioning properly. Turn on the headlights, radio, and other components to verify their operation.
RAC Service and MOT Plan

RAC Service and MOT Plan

From £19 a month†.
Spread car maintenance costs with our affordable monthly plan.
Beat inflation – lock in today’s prices for two years!

†Minimum price for RAC members. Non-member prices start at £21.11.

RAC Service and MOT Plan

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?

There are a variety of factors that can impact the amount of time it will take to charge a car battery.

This includes the amount of power it takes to charge, condition of the battery, and how it was originally installed.

However, the average time it takes is from two to eight hours. In some cases, it can take up to a day to charge.

How much does a new car battery cost?

If you are looking to get a new car battery, there are a few important things to consider.

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

However, the average price starts at around £200 – not including the cost for it to be fitted and tested by a mechanic.

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.

rac forum