Batteries in cars are, in essence, the same as any other type of battery. Any battery is simply a way of storing energy to use at a later date. Your car battery doesn’t drain in the same way as your TV remote control though. As you drive the car, this charges up the battery again, ready to provide power to the car when required. This is the job of the related part called the alternator. Sometimes, a driver may diagnose a battery problem when it’s actually the alternator which is at fault.
When you get into the car and turn the ignition, the battery provides the spark which starts the fuel burning and gets your car moving. The battery also provides the electrical power for all of the other electrics in the car such as the lights, the ventilation system, or the radio.
If you drain all of the power from your battery, and don’t drive enough to give it the opportunity to charge it back up again, then you might get into the car and discover it won’t start at all. This is what is known as a flat battery. It’s unlikely though that this is something that happens all of a sudden, unexpectedly. Usually, there are some warning signs that your battery is struggling to maintain a charge and might need to be replaced. Some of the key signs to look out for are:
Slow starting engine – rather than starting as soon as you turn the key, the engine chugs a few times before finally starting.
Check engine light – this light might appear for a whole host of reasons, but if the light comes on when you’re also finding that the car is slow to start, you should investigate the battery as a first course of action.
Dim Headlights – the battery might be struggling if you notice that the headlights don’t seem to be as powerful as they used to be.
Smell – a battery which is trying to overcharge itself might create a pungent smell like rotten eggs.
Misshapen battery – if the chemical processes have stopped working in your battery, this could cause the casing of the battery itself to become swollen or misshapen.
If you’re not sure whether your battery is causing the problems you are having with your car, then test it before rushing out to buy a new one. Any garage will be happy to do this for you, but will charge you for the work and may try to sell you a new battery whatever the test shows. It’s a fairly easy job to test the battery yourself using a multimeter. A properly charged battery should be showing a range of between 12.6 volts and 12.8 volts. Batteries which are registering a level under 12.6 volts may well be starting to struggle, and might start to cause many of the issues listed above.
Batteries are one of the most commonly replaced items under the car bonnet, and can be bought from all major car parts retailers, garages or direct from manufacturers. Batteries come in all shapes and sizes, and it’s important to get the right one for your engine in order to keep it running efficiently. For example, a modern engine with a stop/start function which cuts the engine off while stopped at the traffic lights will need a specific battery designed for that purpose. Don’t just assume that any old battery will do. The easiest way to check which battery you need is to plug your registration number into our online tool to see which batteries the manufacturer recommends for your vehicle. You can also look in the manufacturer’s handbook, or get advice from your local mechanic or garage.
Fitting a new battery to replace an older one is not a complex job, but in many modern cars the issue is getting to the battery. Modern engines may have the battery hidden deep in the engine cavity, covered by a plastic cover. If you’re reluctant to start messing about under the bonnet, ask your mechanic to help you. If you can get easy access to the battery, it’s simply a matter of disconnecting the clips from the old battery, removing it, and putting the new battery in its place. Car batteries fall into the category of “hazardous waste” so you can’t just dispose of your old battery with the household waste. Take it to your local recycling centre, which will have a space where you can leave old batteries for proper disposal.