How to Charge a Car Battery

Contents:

• Choosing the right battery charger
• What you need to charge a car battery
• Charging a car battery
• Removing your car battery
• Safety precautions
• Common mistake
• Car battery maintenance

If you tried to start your car and it just chugged weakly, or it didn’t even turn over at all, there’s a good chance you’ve got a flat battery. Often, this is just because something’s caused all the power to drain out, and recharging it will solve the problem.

You might have left something electrical on, like the lights, there might be a parasitic drain, or the cold weather might have done it. Otherwise, you might have done a lot of short journeys recently or not used your car for a long time.

When a battery goes flat for a reason like this, you can normally recharge it and get it going again. You won’t be able to fix a battery by charging it if it’s dead and won’t hold charge any more. But if it’s just been drained to nearly flat, you will.  

People also charge healthy batteries for better vehicle performance and to get more life out of them. Old batteries benefit from occasional recharging, for example. It’s also a good idea to charge your battery in cold weather or if you won’t use your car for a long time.

In this article, we’ll tell you everything you need to know about charging a battery in a petrol or diesel car. The batteries in electric vehicles work differently to the batteries in petrol and diesel cars, and they’re not covered here.  

It’s important to make sure you’ve got the right charger for the battery in your car. The best thing is to check in your battery manual to make sure the charger you use is compatible. If you use the wrong charger, you might damage the battery or your car’s electrics. It could also be dangerous.

Regular car battery chargers work by delivering a steady, continuous electrical current to the battery. These chargers lack the advanced, modern features you get with smart chargers.  

Smart car chargers feature technology that enables them to adjust the rate of charge according to the condition of the battery and its state of charge. This technology gives you more effective and safer charging. Smart chargers are particularly good for prolonging the life of a battery, with programs that adjust the rate of charge to achieve the best results.

You need to use a smart charger if your car has stop-start technology.

Here are some other things to know:

• Some car chargers come with a maintenance charging mode or with jump start capability.

• Larger, 24-volt leisure batteries require a 24-volt charger.  

You don’t need many tools to charge a car battery. Here’s everything you need:

• Car battery charger

• Adjustable wrench or socket set (for disconnecting battery terminals)

• Wire brush and contact cleaner

• Safety / mechanics gloves and protective eyewear

A voltage meter is another useful car battery tool that you can use to test your battery after you’ve charged it.

Charging a car battery is a simple job that anyone can do. You just need to make sure you do everything in the right order and you use all the right equipment. Be careful to park your car in a well ventilated area while you’re charging the battery. Garages normally aren’t well ventilated enough for charging a battery.

Before you start, gather all your tools together and put on your safety gloves and glasses. Also, make sure you’ve checked your battery manual to make sure it’s compatible with your charger.

 

Step 1. Turn the car off 

Park your car in a safe, well ventilated place. Then make sure the engine and all the electrics in the car are switched off.

Release the bonnet catch, so you can access your battery.

 

Step 2. Disconnect the car battery

Locate the battery in your car. In most cases, it will be easy to locate underneath the bonnet. It should be easily accessible.

In some vehicles, the battery is in the car’s boot. If this is the case with your car, look in your owner’s manual to see how to locate and reach it.

Once you’ve located your battery, it’s a good idea to disconnect it from your car before you charge it. You might also need to remove the battery from your car for charging if you don't have a power source near where you’re parked. Be careful because disconnecting your battery will reset the electrics in your car. Make sure you know your radio codes, and take a record of any dashboard settings or anything else you’d like to reprogram later on.

Disconnect the connector on the negative (black) terminal first, and move it safely to the side. You may need your spanner or socket set for this part. After that, disconnect the one on the positive (red) terminal, and place it to the side.

Always disconnect and connect terminals in the right order.

 

Step 3. Clean the battery terminals to ensure a good connection

Inspect the terminals on the battery and the negative and positive connectors for corrosion.

If you find any corrosion, give the parts a good clean with your wire brush and cleaner. Then return the connectors to a safe location.

 

Step 4. Connect the charger to the battery

Next, connect your charger to your battery with the charger disconnected from the power source.

Connect the positive (red) cable first. Give it a wiggle after you connect it to make sure the connection is secure. Then do the same thing with the negative (black) terminal.

After that, place your charger on a stable surface as far away from the battery as you can. Make sure you don’t leave it on top of the battery.

 

Step 5. Turn on the charger

Next, you need to turn on your charger.

Make sure the charger is on the right settings. This will depend on the type and model you have. Look at the manual before you switch it on, so you know the correct procedure.

After this, give the battery time to fully recharge.

With regular chargers, this is normally an overnight process. It might be shorter or even longer, depending on the charger you have.

 

Step 6. Turn off the charger and disconnect it

Once charging is complete, turn off the charger at the power supply.

Disconnect it from the battery. Disconnect the negative (black) terminal first, and then disconnect the positive (red) terminal.

Wrap up the cables for your charger and store it away in a safe place.

 

Step 7. Reconnect the car battery

Now, you can reconnect your battery.

Reconnect the positive (red) terminal first and the negative (black) terminal second. You can try starting your car again at this point and give it a test drive if you need.

If you find that your battery still does not start your car after a full charge, it is most likely completely dead and in need of replacement. You will need to have it tested or find a replacement.  

It is possible to remove your battery from your car for charging if it’s more convenient, or if you don’t have a power source close to where you park your car.

Follow the steps above, but after you disconnect your battery from your car’s electrics, also remove it from the car itself. There will be mounts and attachments that hold it in place. Look in your owner’s manual for information about removing the battery. Otherwise, inspect the attachments that hold it in place yourself.

You can then charge your battery in another location. Make sure the charging location is well ventilated, and do not leave your charger near your battery while it’s charging.

It’s important that you follow some basic safety precautions when you’re charging a car battery:

• Work in a well ventilated area

• Wear gloves and protective eyewear at all times

• Make sure the charger is placed away from the battery. Do not place it on top of the battery.

• Do not leave a car charger on a hot surface, like on a radiator, or in the sun.

• Clean your battery terminals thoroughly before you start charging. Using a wire brush and contact cleaners is best.

Charging a car battery is a simple job, but it’s still possible to make mistakes. Some mistakes can also be dangerous. Be careful about what you’re doing.

Here are some of the common mistakes:

• Using an incompatible charger – Using the wrong charger could be ineffective. Otherwise, it could result in damaging or even dangerous overcharging of the battery.

• Connecting the charger or car connectors to the wrong terminal – This can be dangerous or result in damage to the car or battery.

• Not cleaning the battery terminals correctly – Cleaning the terminals properly will help to prevent sparking and make sure that charging is effective.

• Leaving the charger on for too long – Charging a battery for too long could result in overcharging, which could damage the battery or be dangerous.

• Using the wrong settings on your charger – Using the wrong charger settings can result in ineffective charging or potentially dangerous overcharging.

To maintain good health in your car battery, you should try to keep it fully charged.

All car batteries will benefit from occasional charging with a trickle charger, a smart charger or a maintenance charger. These car battery chargers charge slowly, with a low electrical current, which is ideal for prolonging the life of the battery. Some smart chargers can even repair car batteries by reversing sulfate build up inside the battery.

It’s a particularly good idea to occasionally charge your car battery if you do not use it very often or if you take it off the road for a long time. It’s also a good idea to regularly charge your car battery in the winter when the weather is very cold.  

You can also use a car battery tester to test the condition of your battery.

If your car battery has been drained of energy, giving it a recharge should get your car going again. Usually, this means a long, overnight charge, but your battery will return to the same condition it was in before. This won’t work with a completely dead battery, but with a mostly flat one it will.

You can use a regular or a smart car battery charger for the job. Just be careful to make sure you follow the steps set out in this guide so that you work safely and charge your battery effectively.

It’s also a good idea to give your car battery a charge from time to time to keep it in good condition. Smart chargers, maintenance chargers and trickle chargers are all ideal for this.