What every driver should know about car batteries

If you’ve ever turned the key of your car only to find it won’t start, you’ll know how much of a pain a flat car battery can be. If you’re unable to get off your drive, it can easily ruin your day’s plans or stop you from getting in to work on time. If you don’t have the knowledge to get your car running again, you may have to wait days before you can get hold of a professional to look into the problem for you.

To make sure this never happens to you, you should make sure to learn as much as you can about your car’s battery. We’ve put this guide together to give you all of the information you need, and in it, you’ll find out:

  • Exactly what a car battery does, and why it’s such an important component of your car
  • What to do when you find yourself with a flat car battery
    • How to perform a push start
    • How to perform a jump start
  • When and how to replace your car’s battery
  • When and how to recharge your car’s battery
  • How long car batteries last
  • How you can prolong the life of your car’s battery
  • How to dispose of a used car battery

Armed with this information, you’ll be able to do everything you can to prolong the life of your car’s battery, as well as get yourself on the road as fast possible if you ever do end up with a flat. Read on to find out everything you need to know.

How does a car battery work?


The battery in a car starts the engine with a short burst of strong voltage. Without it, the car cannot start. While the car is running, the battery works in conjunction with the alternator to power the electronics within the car, which is a lot more taxing in modern cars than it was in the vehicles of the past.

While the car runs, the alternator reverses the current produced by the battery, which recharges it. This is only the case during long journeys, however, and if you rarely drive for longer than 15 minutes, your car’s battery won’t get a chance to recharge properly.

By far the most common type of car battery is known as a ‘wet’ or ‘flooded’ battery. These consist of lead plates suspended in an acid solution, which produces the charge necessary to start the car and power its electronics. Most modern car batteries are maintenance free (MF), which means that they require no upkeep at all during their lifespan. While they’re made of hundreds of micro-components and serve such a crucial role in powering your car, maintenance-free wet batteries are relatively cheap and totally hassle-free to use.

How long do car batteries last?

A well-looked-after battery can last up to five years, while a neglected one may only last half that time. Driving habits and frequent exposure to extreme weather conditions can affect your battery’s lifespan.

One thing to keep in mind is that modern stop-start technology saves you a lot of fuel, but places a greater strain on your battery. If your car has this feature, you should expect the lifespan of its batteries to be shorter than you’ve become accustomed to.

What to do when your car battery goes flat

If you turn the key in your ignition and your car’s engine turns over but doesn’t start, or if it shows no sign of life at all, chances are that your battery has gone flat. While this is an inconvenience, it isn’t the end of the world, as a push- or jump-start will at least get you from A to B in the short term.

However, before you attempt to start your car, you should open its bonnet and inspect the battery. Don’t make any attempt to start your car if:

  • You’ve charged it and it still isn’t working.
  • It’s leaking. If there is a strong eggy smell coming from your battery, that means it is leaking – it’s the escaping sulphuric acid that is producing the unpleasant odour. A leaking battery should be replaced immediately, and when doing so, you should wear protective gear at all times.
  • The casing is cracked. Check to ascertain the cause of the damage to prevent it from happening again, and then replace the battery immediately. Again, wear protective clothing when you’re dealing with any damaged battery, as you won’t want to make contact with the acid.
  • If the end walls of the battery are swollen after the car has stood dormant for over a month. The battery is likely to be sulphated due to being left in a discharge state.

However, if your battery shows none of these symptoms, you’ll be safe to attempt to get it going and go about your day. Your first option is the push-start.

How to push-start a car

The first method of getting your car moving when its battery is dead is a push start, also known as a bump start. You’ll need to recruit the help of some volunteers or have your passengers give you a hand and get your car rolling by giving it a push.

You should not be tempted to try to perform a push start on your own by pushing your car down a hill by yourself and then trying to jump in the car as it’s moving. You can not only seriously injure or embarrass yourself when attempting to enter the moving vehicle, but you can also cause an accident if your car ends up rolling down a hill without a driver at the wheel.

Here’s how to perform a push start:

  • Disengage the handbrake, put the car in second gear, and hold the clutch down fully.
  • Hold the key in the ‘on’ position.
  • Have your volunteers push the car, ideally with the help of a hill.
  • When the car reaches 5–10mph, release the clutch and press the accelerator. If you’ve done everything right, the engine should catch and you’ll be on your way.

Please note: you won’t be able to push-start an automatic car. You also shouldn’t attempt to push-start a vehicle with a catalytic converter, as unburned fuel mixture in the exhaust may damage the engine.

After you’ve got your car going with a push start and you’ve driven for around 15 minutes, your battery should have recharged enough that it will start without any assistance next time.

Another way to start a car with a dead battery is with a jump start.

How to jump-start a car


To jump-start your car, you’ll need a pair of jump cables. So you don’t have to rely on someone else owning a pair and helping you out, you should always keep some in your car. Buy jump cables from our online store today so you’re never stuck without the ability to start a dead battery.

Before you attempt to jump-start your vehicle, you need to bear in mind that safety must come first and foremost. You’re going to be working with a high-voltage electrical current, so if you’re unsure about what you’re doing and don’t feel confident performing the operation, call a professional rather than risking your own safety. If you are going to attempt your own jump start, here are the safety rules that you must abide by:

  • Never attempt to jump-start a battery that is damaged, corroded, or visibly leaking.
  • Don’t use jump cables that are damaged, as broken conductors or damaged clamps can overheat and even catch fire.
  • Never smoke around a car battery, as they release flammable gasses and an explosion could ensue.
  • Remove all jewellery, and keep all metal objects away from the battery, as if they brush against the battery posts they will cause a spark that could lead to an explosion.
  • Remove all loose-fitting clothing such as scarves and neckties in case they get caught in the moving parts of the engine, which can cause serious injury.
  • Remove the key from the ignition and make sure all of the car’s electronics are turned off.

With all of these rules in mind, you can begin the jump start. Here’s how:

  • Find a Good Samaritan who’s willing to lend you their car and a few minutes to give you a jump start.
  • Go through the safety checklist above to ensure the wellbeing of yourself and the person helping you.
  • Park both cars beside each other. They should be close enough that their batteries can be connected with jump cables, but not touching.
  • Connect the red jump cable to the positive terminal of the working battery, and the other end to the positive terminal of the dead battery.
  • Connect the black cable to the negative terminal of the working battery, and the other end to an earthing point. This can be anything metal, such as a bolt or bracket, away from the dead battery. Check your car’s users’ manual to see if your car has a negative jump-starting pole, as they’re a feature of many modern cars.
  • Make sure the leads are out of the way of all moving parts and start the engine of the working car.
  • After a minute or so, try to start the car with the dead battery. If it doesn’t start, wait another few minutes and try again. Your problem may not be with your battery if it still doesn’t start, so call a professional to get their expert opinion.
  • If the car with the dead battery has started, leave both cars to idle for 10 minutes in order to charge its battery. Don’t remove the jump leads while the engines are running, as this could cause irreversible damage to the electronics of both cars.
  • After around 10 minutes, turn off the engines of both cars and disconnect the cables. Again, this should be done in a very specific order: the black cable from the earthing point, then from the negative terminal of the working battery, followed by the red cable from the dead battery and then from the working battery. Make sure not to touch the leads against each other, either car’s bodywork, or anything metal, and only handle the insulated parts of the jump leads.
  • Start your car again and then drive it for at least 15 minutes in order to recharge the battery fully. Don’t turn the engine off before the 15 minutes are up, as if you do, the battery might not receive enough charge and you will have to go through the process again.

While performing a jump start isn’t complicated, it can be incredibly dangerous for those who don’t take the correct precautions. Go through the process slowly and diligently, and you should have no problems. If you successfully complete all of these steps and your car still does not start, your battery may not be your issue, and you should seek the advice of a professional before attempting another jump start.

Keep in mind that both a push and jump start are just temporary fixes to the problem of a dead battery, and they can cause permanent damage to your car if you continue performing them on a long-term basis. For a permanent solution, you’ll need to change the battery for a new one.

When should I replace my car’s battery?

If your battery is over five years old and your car is struggling to start, it’s likely the battery is reaching the end of its life. It’s much more sensible to replace the dying battery in your own time rather than having to deal with the inconvenience of waking up to a car that won’t start one day, or potentially having to foot the bill for a roadside breakdown repair.

Be aware that you may be having problems with your alternator rather than your battery if your car isn’t starting. However, unless you’re certain this is the case, don’t make any repairs without consulting a professional first, as you could end up wasting a lot of time and money if you’re mistaken.

How to replace a car battery


When replacing your car’s battery, make sure that you get the correct type for your make and model of car. Check your vehicle’s owners’ manual to find out which battery your car requires.

Alternatively, simply enter your registration number into our car parts search to find the exact battery for your car.

How to replace a car battery

  1. Purchase the replacement battery. You can find the battery you need for your exact make and model of car with our car parts search.
  2. Wear rubber gloves and goggles before making the repair to ensure that no battery acid makes contact with your skin or eyes. Take a look at our range of body protection products if you don’t already own any.
  3. Remove the old battery. First, disconnect the cables, remembering to always remove the negative connection first. Take out any screws holding the battery in place, and then lift the battery out of the car by holding down the clamp, which will be found either on the top or along the side of the battery.
  4. Give the battery tray a wipe down with a damp cloth, and then apply a primer, such as this one from Tetrosyl, to keep it from deteriorating.
  5. Place the new battery in the battery tray, put the clamp back on, and screw it in place. Clean the cables with a wire brush, such as these from Sealey, and then attach them to the new battery, positive before negative.
  6. Make sure your new battery is working by turning your car on.

Can a flat car battery recharge itself?

While it’s true that your battery is recharged while your car is running, simply starting your car and leaving it to tick over won’t provide enough power to the replenish the battery. In fact, this will probably use up more battery power than it generates. Other than taking your car on a longer journey, which is impractical if you weren’t planning on doing so anyway, the only way to properly recharge your battery is with an automatic battery charger.

While these chargers often have a fast-charge option that can recharge your battery in an hour or so, it’s not recommended that you use this unless you absolutely have to. This is because it heats the battery up to a point where there is a build-up and release of hydrogen gas, which both damages the battery and poses a potential safety risk.

Instead, it’s recommended that you use the slow-charge option, which will take 10 to 15 hours depending on the make and model of your battery. This won’t put your battery through the strain of the fast option.

The typical car battery is not a ‘deep cycle’ battery — it is not designed to be frequently drained and recharged, but to provide a high current to get the engine started and then rely on the alternator for extended power needs. That being said, it is possible to recharge the average car battery a few times before it is no longer usable, making a battery charger a good investment, especially for households with more than one car. Go for a good-quality model from a reputable brand that switches to a trickle charge once your battery is fully charged. Pick one up from our wide selection of car battery chargers.

How to dispose of a used car battery

Due to their toxicity, it’s illegal to dispose of used car batteries with general waste. Visit the government website to find out whether your local council offers a disposal service that you can take advantage of. If not, use the Recycle Now recycling locator to find the nearest place you can safely dispose of your old car battery.

How to prolong the life of your car battery

While your car’s battery will inevitably run out eventually, there are a number of things you can do to prolong its lifespan and save yourself some money.

Firstly, one of the most common causes of a drained battery is drivers leaving their headlights on overnight. Double-check that your lights are turned off whenever you’ve been driving with them on to avoid running your battery down.

While your car is running, the alternator feeds energy back in to it, recharging it. The longer you drive your car in one sitting, the longer your battery has to recharge. If you only ever use your car to go on short journeys, it never has the chance to recharge fully, which will shorten its lifespan. A battery that never has a chance to recharge fully may only last half as long as one that is frequently fully charged, so if possible, make sure to often use your car for longer journeys if you only use it for a short commute ordinarily.

Also, if a car stands for a long time unused, its battery is likely to die due to a lack of charge. Try to avoid leaving your vehicle unused for any longer than a fortnight, or you may find it not working when you do come to use it.

If your car is often left for long periods without being used, simply removing the battery’s negative connector will go a long way to stop it from draining. An even better option is to invest in a smart charger or an eco-friendly solar trickle charger, both of which you can pick up from our range of battery tools.

Why is a car battery more likely to die in cold weather?


Colder temperatures cause the chemical reactions that occur inside a car battery to proceed at a slower rate, which means that an already weakened battery is more likely to die in cold weather. If you have a garage, it’s a good idea to keep your car inside of it so the battery is kept at a warmer temperature. If you don’t have a garage, it’s recommended that you keep your vehicle parked in an area that doesn’t get much wind chill if at all possible, as well as to use a car cover to keep its temperature as high as you can. Browse our full range of car covers here.

What to do if your battery is coming to the end of its life



Most cars have a low-battery warning light on the dashboard (pictured above). If this stays on after ignition, then you should inspect your battery as soon as possible, as this is a sign that it is coming to the end of its life.

If you get the low-battery warning light or can sense your car battery’s performance worsening, be sure to check the terminals for signs of dirt, corrosion, or excess grease, as this can weaken the circuit between the battery and your car’s electrical system. Remove the terminals and clean them with a dedicated battery post and terminal cleaner, such as this one. Remember, always remove the negative terminal first and reattach the positive terminal first.

If you’ve cleaned the battery’s terminals and it’s still performing sluggishly, you can give it a helping hand by turning off all electronics such as the heating, radio, and satnav to give it less to do as it starts your engine. You can turn these on again once your car is running. Bear in mind that this is just a short-term solution, and you should replace the battery as soon as possible when you sense a dip in its performance.

Keep all of this information in mind and you’re sure to get the most from your car battery, as well as know exactly what to do if you ever find yourself with a car that won’t start. If you’d like more information about car batteries, don’t hesitate to get in touch with a friendly member of our team today.

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