The Ultimate Guide to Car Batteries

Our cars wouldn't go anywhere without batteries. That's why we need to take extra care of them, especially in the winter months.

A fully-charged battery can struggle enough with the cold, so you can likely imagine how an undercharged or failing one would fare. But how much do you know about car batteries?

By the end of this article you will understand:

• What a battery does
• How long they last and what affects their lifespan
• What the battery warning light means
• How to dispose of a used car battery
• How much a car battery costs
• And so much more

 

Glossary

Electrode - A conductor that makes contact with the nonmetallic part of any circuit. Electricity enters and exits through electrodes.

Cathode - The negatively charged electrode (has more electrons than protons). This is where electrons enter an electrical device. While a battery is charging, it becomes positive.

Anode - The positively charged electrode (has more protons than electrons). This is where electrons leave an electrical device. While a battery is charging, it becomes negative.

Electrolyte - A substance that can conduct electricity when it forms a solution (usually with water). It has a balanced number of protons and electrons and so is neutral.

 

Summary

Car batteries have a 'wet cell' design. This helps them start your vehicle, stabilise the voltage that keeps your engine running and convert chemical energy into electrical energy. They should last between 3 and 5 years, but excessive short journeys or long periods of inactivity can reduce this.

If the voltage reaches 11.9 or less, the battery is classed as dead (it should usually have 12.7 volts or more). When this happens, you need to replace the battery. You can either do this yourself or get a professional mechanic to do it for you.

If you do it yourself, you must fully disconnect the battery and dispose of it at an official refuse centre. This could be a scrap yard, garage or local recycling facility (if they have the right facilities). You won't get much for a battery as scrap metal and can expect to pay around £150 on average for a new one.

 

 

What Are Car Batteries Made Of?

Car batteries use a 'wet cell' design. These have 6 cells, each of which contains alternate plates made of a lead alloy grid. Inside each cell is a cathode plate or an anode which is usually lead dioxide. These are then submerged in a sulfuric acid solution, which acts as the electrolyte.

 

 

 

What Does a Car Battery Do?

Your car battery powers all your vehicle's electrics. It also provides the spark to start your car in the first place.

Its main jobs include:

• Converting chemical energy into electrical energy
• Delivering voltage to the starter
• Stabilising the voltage that keeps your engine running
• Providing power for electrical parts to work

 

How Long Do Car Batteries Last?

The average car battery lasts between 3 and 5 years. With extra care and attention, yours could last up to 10 years.

However, the following can significantly reduce your battery's lifespan:

• Long periods of inactivity
• Vibrations from rough roads
• Temperature extremes. Batteries produce 35% less current during cold weather, according to CTEK
• Lots of short journeys

These factors put extra strain on your battery and disrupt the chemical reaction that generates a charge. A significant problem with your battery will cause the warning light to show up.

 

What Does the Battery Warning Light Look Like? (And What Does it Mean?)

 

 

The warning light means that the battery is not charging properly. Usually, this is because of a fault in the alternator. This usually charges the battery while you drive along. If you see the warning light, your battery is running on its own charge which will eventually run out and create a dead battery.

 

What Voltage is a Car Battery Supposed to be?

When it is fully charged, it should have 12.7 volts or more. A car battery that needs recharging will have a voltage between 12.2 and 12.6 volts.

Once the voltage falls below 11.9, it is considered dead.

 

What Do I Do About a Dead Battery?

If you or a technician tests your battery and it reads as dead, you might still be able to recharge it. However, it is unlikely to hold that charge for very long. You might be able to drive your car to a garage, but you will probably have to do so immediately and without turning the engine off at any point.

To fix a dead battery, you will need to buy a new one and have it fitted. This can either be done by a qualified mechanic or you can do it yourself if you feel confident enough.

 

How Can I Prevent This?

A dead battery is inconvenient and can leave you stuck by the roadside for several hours. Once you get towed to a garage, you'll have to pay the first repair quote that you're offered because you can't live without your car. This means that you're unlikely to get the best deal.

Fortunately, it's easy to prevent this stress.

Book our 17-point Winter Health Check at a garage near you to get peace of mind about the quality of your battery. It's designed to get your car ready for winter and, as we're 51% more likely to suffer a battery problem at this time (according to the AA and AXA), a thorough battery check is included. If you have any concerns about your battery, you can leave additional notes asking for a further inspection.

If there is a problem, you have the time to compare repair quotes and find the best deal before your battery dies. Plus, over 700 garages on our comparison site offer this check completely FREE of charge, and over 1,000 offer it for less than £25. That means you get peace of mind for less and stay in control of your car maintenance in the run-up to Christmas.

 

 

How Do You Disconnect Your Battery?

If you choose to replace a dead battery yourself, the first thing you must do is make it safe to use. This involves disconnecting it from the rest of the car. If you have safety goggles and gloves to hand, you might want to use them to help you during the process. To disconnect your car battery you must:

1. Turn the Ignition off.
2. Find the Negative Battery Terminal. This is usually black and has a black plastic cap marked with a "-" sign.
3. Loosen the Nut on the Negative Terminal. Not every battery uses the same terminal so you may need a range of wrenches to choose from. Once you've found the right one, use it to loosen the nut by turning in a counterclockwise direction.
4. Remove the Negative Connector. Once the nut is loose, remove the cable and push it far away. You don't want it to touch the battery again until you're ready.
5. Repeat the Process With the Positive Terminal.
6. Remove the Battery. Now that the battery is disconnected, you can remove it from the engine to replace it.

 

How Do I Dispose of a Used Car Battery?

Battery acid is highly corrosive, so you must dispose of a used car battery properly. By law, you can't dispose of one in household waste. You have to take it to a facility that is equipped to handle car batteries. This means disposing of them at:

• A scrap metal facility
• A garage
• Or a local recycling centre

You can't get rid of a used car battery anywhere else.

 

How Much Are Batteries Worth as Scrap?

Car batteries aren't worth that much as scrap. There are plenty of them around, so the average scrap metal price is between £300 - £600 a tonne.

Batteries weigh between 30 and 50lbs (0.01 - 0.02 tonnes) so you shouldn't expect to get more than £5 to £10 for an old battery when you sell it for scrap.

 

How Much Is a New Battery?

A new battery costs £150 on average in the UK, with the price ranging anywhere from £100 to £350.

It only takes 15 - 30 minutes to fit a new battery, so you shouldn't expect to pay a full hour's worth of labour either. This means the average UK battery replacement should cost less than £200.