There are some car repair jobs you cannot do yourself. From repairing timing chains to replacing brake discs and fixing windshield cracks, it can often be essential to take your car to a professional mechanic. A job done well for a cost is always better than a job done improperly for free — especially when it comes to vehicle safety.

But, there are some jobs you can do yourself without experience. Car battery replacement is one of them. Our experts offer advice on how to change a car battery at home.

Why Replace a Car Battery?

The majority of cars have batteries. The only vehicles that do not have traditional car batteries, funnily enough, are electric cars. These cars have special batteries that power the entire vehicle, which means their structure and use is different from your typical car battery.

In a petrol or diesel-powered car, the battery is responsible for operating all electrical systems in the car. Cars may run on fuel, but that does not power things like lights, air-con settings, your stereo, seat warmers and other tech offered by some vehicles. You need electricity to enjoy these features, and that electricity comes from the battery.

The engine charges car batteries as it runs. The engine is effectively a self-contained electrical turbine. The charging system uses an alternator to feed energy into the battery. This process means the vehicle can power the battery for the entire life of the car, as long as it is running. The thing is though, as with all electronic devices, use will inevitably lead to problems. Your phone battery becomes inefficient the more times you use it, and the same can be said of car batteries. Eventually, a lifetime of wear and tear can build-up and the delivery system of electricity starts to fail within the vehicle.

It's the end of the road for your battery, but not your car.

When Does my Car Need a New Battery?

When a car battery no longer works properly, you can replace it. But how do you know when to ditch the old battery and buy a new one? It is suggested you put a new battery into your car every three to five years, although there are other indicators if it needs replacing sooner. These include:

• Difficulty starting your car — If your car struggles to start, it may be due to a faulty battery.

• Check engine light — If your battery isn't working properly, the car's feedback systems may alert you to the fault using the check engine light or car battery symbol.

• Fluid leaking — Fluid leaks from the battery are a clear sign it needs replacing.

How to Prepare for Car Battery Replacement

You only need a few pieces of equipment for a car battery replacement job. Most of these you'll likely have to hand, but they can be ordered online or purchased in stores for a relatively low price. To change a car battery, you'll need:

• Old clothes or clothes you don't mind getting dirty. Going into a car engine bay is rarely a clean job.

• An adjustable wrench. Wrenches may be required to access battery cover cases and disconnect battery terminals.

• A ratchet wrench is an essential tool necessary for removing batteries from their mounts. You may also need an extension bar if you find yourself in a situation where you cannot reach the bolts with a standard wrench.

• Gloves and safety goggles are optional extras for health and safety purposes. Note they can be important for removing car batteries, especially if it has been damaged or is very old.

• A well-ventilated space is essential. Most batteries for stop-start ignitions emit a gas vapour that needs to dissipate safely. 

Where to Buy Replacement Car Batteries

You can buy a replacement battery for your car here on the YMF Car Parts website. Enter your registration number and navigate to our car and van batteries page. Here, you'll find options for car batteries that fit with the exact make and model of your car perfectly. You don't need to worry about buying the wrong battery for your vehicle — you'll always find the right products with YMF Car Parts.

Expect to pay between £50 - £200 for your new car battery.

Changing a Stop-Start Battery System

Before you begin battery replacement, it’s important to be aware of the differences between a conventional battery and both AGM batteries and EFB batteries. The actual physical replacement process is the same, as the batteries are designed to fit into similar areas of a vehicle. However, the replacement of an AGM or EFB battery requires extra attention. These batteries are present on most newer cars with advanced electrical systems — usually, 2010 or later but possibly earlier for luxury cars. The most common system you’ll see that suggests the use of an AGM/EFB battery is stop-start technology. However, these batteries can also be present on cars without stop-start that have modern on-board computers.

How do you know if you have an AGM or EFB battery? The best way to learn exactly what battery your car has is to open the engine bay and look for the product information detailed on the battery itself. A conventional battery is an acid battery. If it’s not an acid battery, it will often state if it’s AGM or EFB. 

If in doubt, check your manual, run a search for the serial number on the battery, or ask an expert. Don’t proceed until you know exactly what battery your car uses. 

The first thing to know is you must get the correct type of battery for your car. You can’t buy an EFB battery for an AGM-operated vehicle — it won’t work. 

The other important thing to note is these types of batteries connect to the stop-start system and the battery management system (BMS). Disconnecting and reconnecting a battery from these systems will cause them to reset. You must follow the correct processes here, or the on-board computers may malfunction, including damage and possible loss of the stop-start ability of the car. 

This process will be outlined in your owner's manual, as it varies from vehicle to vehicle. If you cannot find this, we recommend looking for online tutorials or guides relating to your exact make of car. Still not able to find the information you need? Don’t continue with the job — take it to an expert. 

How to Change a Car Battery: Steps to Follow

The first step is to make sure your car's engine is off and the key is not in the ignition, so no power is running into the battery, and the engine system is cool. This means you’ll have to avoid making the battery replacement until a few hours after driving. The parking brake should also be up.

Next, open the engine bay and locate the battery. Car batteries often have grey or black plastic casing with red or blue detailing. They can be found almost anywhere in the engine bar but often are near the headlights. If you can't find the battery, check your owner's manual. Some car batteries are in unusual places, including under seats or in the boot.

You will need to disconnect the car battery terminals from your car. The battery will have a positive terminal and a negative terminal — this is similar to your standard AA battery. To find the positive terminal and the negative terminal, look for battery leads (wires) connected to either side of the car battery, usually covered in black rubber lining. They may be hidden under a plastic case. 

IMPORTANT:

• Disconnect the negative terminal first — the minus symbol
• Always disconnect the positive terminal last — the plus symbol

The terminals may have clamp components you can unclip, or you may have to unbolt them using a wrench. Once the electrical supply leads are disconnected, secure them safely away from the battery.

Once the car battery is disconnected from the system, you'll need to remove it from the vehicle itself. The battery connects by a metal bracket fixed to the engine bay with bolts and screws. You'll need a ratchet wrench to undo the bolts to release the car battery. You may need a wrench extension bar to reach the bolts if they are in difficult to reach areas.

Now put on your gloves and goggles. Why? Because battery acid is corrosive and if there is any unseen damage to the car battery, contact can cause burns to your skin and eyes. Remove the battery carefully by lifting it out of its placement within the car and place it flat on the ground on an even surface to avoid it falling over. Car batteries can be heavy — around 10 kilograms at least — so be prepared to put your back into it.

You can now fit your replacement car battery. Fit it to the old battery tray then connect the positive terminal only. Do not reconnect the negative terminal yet. Bolt it back down to the engine bay using the original clamps and fittings. Replace any covers and fix every bolt removed or loosened during the battery change process. Ensure you put everything back as it was. There may have been other cables or items connected to the negative terminal that are not the negative lead. 

You can now reconnect the negative lead. 

Once you are happy the battery replacement has been completed, make sure you haven't left any tools or equipment inside the engine bay. You can then close your hood and start the car to test it out. Now is the time to check all electrical systems, such as the radio, clock, windows and headlights. Be aware that if your car has a security radio code, you may have to re-enter it.

How to Dispose of a Car Battery

Car battery disposal must be carried out responsibly under the right conditions. The reason is a car battery contains hazardous material, which you don't want to end up in the wrong place. You can't just throw batteries away. A car battery must go to a specialist location for disposal. You can take your old one to a recycling centre, scrap metal service provider or garage. There will likely be a charge for this disposal, however, don't ignore this cost. It is against the law to put your car battery in your standard rubbish or recycling bin. You risk legal prosecution if caught.

Don’t want to pay to dispose of your car battery? At YMF Car Parts we’ll dispose of your car battery for free. Just bring it down to your local brand. You can find all our branch information on our contact page. 

Seeking Professional Help for New Battery Installation

If the removal of batteries in a car does not sound like a job you are comfortable doing, then we recommend you seek help from a professional mechanic. Battery replacement is an inexpensive task that can be completed quickly and effectively by your local garage. Never perform maintenance or repairs on your vehicle if you are not confident in your abilities. When in doubt, go professional.

Click here to purchase car batteries from YMF Car Parts