A car battery is a rechargeable power source needed to start a vehicle and power its electrical components at the press of a button or turn of a key. Without the battery, your car just won't start. Once up and running, it also continues to power various systems like stereos, dash-cams, sat-navs, phone chargers and external/internal lights – as well as all other electrical items.

Your car battery will recharge automatically as you drive it but, for this to happen, you'll need the alternator and drive belt to be in good condition.

Car batteries are usually located in the engine bay under the bonnet. In some cases, however, they can be found elsewhere – such as in the boot, under the floor.

Car batteries store a chemical form of electrical energy, then release it in a controlled way as a direct current. Some cars have start-stop technology, which is where the engine will turn off if the car is stationary. If your car has this feature, it still uses the battery to power its dashboard and in-car technology.

The failure of a car battery is a common reason for breakdown call outs. The reason why it’s such an important part of a car is because it generates the current to power the starting motor. Without it, the engine won’t start – and your car won’t move. The electrical system used to control your dashboard won’t work without your battery, either.

As you start your car, the first half-turn of the key fires up the vehicle. Lights on the dashboard will start to illuminate, the air vents can start blowing, and the radio will come on. This is down to the battery. Headlights or interior lights can also be switched on when the key is half-turned.

The lifespan of a car battery depends on a number of factors. This includes the type of vehicle, level of exposure to extreme weather conditions and your driving habits.

Related: Battery lifespan guide

Car batteries self-charge from a running engine. If a car is sat idle for some time, a battery will lose charge. This is more apparent in older batteries – but additional equipment such as alarms and immobilisers can also drain the charge of a battery.

If a battery is completely flat, the engine won’t turn over so the battery may need charging by using car battery chargers. These attach to the terminals of a car battery and charge it through the electrical mains. Terminals must be connected to the appropriate electrical lead. Not sure? Check your car's handbook or get it checked by a professional in one of our branches.

Yes – your car battery will start to charge if the engine is running. Of course, running any other electrical systems will still drain it.

A substantial amount of power is needed to start your engine so it's recommended that you drive your car for around 45 minutes at 70mph to get the battery to 90%+ of its fully charged state – depending on the age of the battery. Quick trips will not be enough to charge a car battery.

The size of a battery is important when choosing one for your car. The group size refers to the battery's dimensions – including the terminals and where they can be found. This all needs to be considered when you buy a car battery. You can usually find this information in your manual.

For installers, car battery replacement is becoming increasingly tough, longer to complete, and even more specialised. Technology is moving forward at a staggering pace. Car batteries must be made for newer vehicles – more than 70% of which use start-stop technology.

A start-stop battery supplies the starter motor with a larger current to allow a car to restart at the press of a pedal. Unlike a regular battery, this technology is sometimes called micro hybrid because it automatically switches off a car's engine when the vehicle is stopped. The point is to save fuel and help car manufacturers to cut CO2 emissions.

If your car has this feature and an AGM battery fitted, the replacement battery must be of the same technology and offer no poorer electrical performance. It's essential that the correct battery is fitted. If not, this will result in the vehicle not working.

A standard battery isn't meant to be discharged and recharged on a cycle in this way. It's only designed to start the car. So, AGM batteries can be replaced with AGM options while AFBs can be replaced with either AFBs or AGM batteries.

Related: What is the difference between Flooded, AGM and AFB batteries?

A standard starter battery is designed to generate a high-level electric current to start a car. Car batteries focus more on starting an engine but leisure batteries are designed with durability in mind. Leisure batteries can be used to power electrical appliances in caravans and motorhomes – providing a consistent supply of power over a longer period.

There are many reasons why your car battery might keep going flat. The most common causes are corroded or loose connections, excessive electrical drains, or power demands on an alternator. Charging problems could also be the reason why you have a flat battery all the time.

Do you think that your car battery is dead because your car won't start? A potential option is to use jump leads to connect your flat battery to another car's charged battery.

You'll need to ensure that the leads are connected, noting the correct polarity: (+) and (-). It is also essential to refer to the manufacturer's handbook first. The ECU (engine control unit) in some cars can be damaged if they are jump-started so always check the handbook to see if that is the case for your vehicle.

Related: How to jump start a car

Ever gone to start a car to find that it's unresponsive and lifeless? If this is the case, the culprit is most likely to be a flat car battery. For more details, read our expert guide on how to start a car with a flat battery.

If a car battery is not recharging, this can indicate a mechanical issue. This is most likely going to be with the alternator, which should be generating energy to charge the battery.

If you have a multimeter, you can test your car battery at home. When using a multimeter, it's important to be aware that your battery should have no fewer than 12.6 volts.

Of course, there is another option if you want your car battery testing. Simply pop down to your local National Tyres and Autocare branch for a FREE battery test. Our technicians use the latest equipment to test a battery's voltage, start capacity and condition.

Related: How to test a car battery?

With the right tools and information, it's possible that you can fit a car battery replacement yourself. We even have a helpful guide on how to change a car battery for you to use. But our advice will always be to book in for an appointment and let our expert installers take care of everything.

There are many ways to charge a car battery at home, at work or wherever you find yourself. In some cases, however, a dedicated charger may be needed. For more details, see our expert guide on how to charge a car battery.

A battery charger is a device that forces an electrical current (amps) through a flat battery. As you switch it on, a needle on the charger jumps to the desired amps. It then moves down as it charges the battery. When it gets to around the halfway point of the desired amps, the battery is fully charged.

A car battery voltage should be at least 12.6 volts if it's fully charged. Action will be required to recharge the battery once it's less than 75% charged and/or it reads 12.45 volts or fewer.

Not sure what voltage your car battery is? Is your battery showing a low reading? Pop into your local National Tyres and Autocare. One of our friendly technicians will be happy to carry out the necessary checks for you.

All plug-in electric and hybrid cars use lithium-ion batteries or nickel-metal hydride batteries. These store energy over time, so have a much greater energy capacity.

Car batteries have two main cycles. The first is a charge cycle that occurs when you're driving and charging the battery. The second is a discharge cycle that occurs when a battery uses its stored energy.

Battery terminals are the positive (+) and negative (-) post-like structures that you'll find either at the top or to the side of a car battery. Some batteries actually feature both and are known as 'dual terminals'. It's also worth noting that these terminals come in different sizes.

If you need to jump-start a battery, you'll first need to connect the positive terminal before the negative one. If you do it the other way around, you could short the circuit.

Our advice would always be to let one of our specialists disconnect and remove the battery for you. If you need to do it yourself, however, there are a few important steps to follow first. Our guide on how to disconnect a car battery has all the information that you need to do it safely.

You should never dispose of car batteries in a household bin. Not only is this dangerous due to the hazardous waste but it is also against the law.

Most landfill sites and household waste centres will accept used car batteries

An alternator is commonly associated with the battery. It converts the engine's energy into an electrical current for the battery. This in turn powers the electrical system. For this reason, your alternator can be a good first place to investigate if your car battery isn't working.

CCA is the rating that states a battery's ability to start a car's engine in cold weather. This is also referred to as 'starting capacity'.

RC is the time in minutes that it takes for a battery to discharge 25 amps while maintaining at least 10.5 volts.

Ah is the number of amps that the battery can provide over a period of 20 hours – e.g. a 100h battery can deliver five amps for 20 hours.

AGM is a material made up of glass microfibers. It's used as a separator in a battery – with the microfibers absorbing the battery acid (electrolyte) to avoid spillage.