How To Charge A Car Battery

Car batteries can lose their charge for a number of reasons and it’s a good idea to keep it charged up to avoid any problems. If you are new to charging batteries, below we walk you through each step on how to charge a car battery at home.

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How To Charge A Car Battery
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Whether you’ve left the lights on or simply haven’t driven your car in months, the battery may lose its charge. Even if you have a car battery that’s top rated, it can still lose its charge if it’s using power without the car running. However, rather than calling your recovery company, you can easily charge the car battery yourself with the use of a charger.

If you haven’t bought a charger yet, we would highly recommend any of the chargers by the CTEK brand. As you can see in the image above, we have connected it to a dead battery and the charger provides us with indicator lights, powerful charging and a range of safety features to make charging a car battery stress-free.

Below are our recommended steps on how to charge a car battery with a charger.

How To Charge A Car Battery

1. Check The Charger Is Compatible

Depending upon the battery your car uses will highly depend upon the charger you need to use. For example, if your car features stop/start technology, it will use either an AGM or EFB battery. This means that a standard/old charger won’t be compatible and you’ll need to use a newer and up to date charger. If you already own a charger, it should clearly state on the instructions the battery types that it can charge.

2. Check The Contacts (Optional)

Checking the contacts of the battery is always advised because overtime, they can become dirty or corroded. If you find that they could do with some attention, use a wire brush to give them a quick clean. You will also want to wipe away any residue before you begin to charge the battery.

3. Disconnect The Car Battery

Although you can charge your battery whilst connected, it’s always good practice to remove the battery if possible. To disconnect the battery, remove the negative (black) lead first and reconnect it last. This helps to avoid any unexpected shocks when you come to connecting the positive terminal once the battery is charged.

Once you have successfully removed the battery lead, move it to one side (like we have done in the image below) to avoid it touching the terminal as you remove the battery or charge it in situ.

how to charge a car battery with a charger

4. Connect The Charger

With the battery terminal(s) disconnected, you will want to connect the charger. We recommend keeping the charger switched off at this point for complete peace of mind.

Whilst connecting the charger, as simple as it, you want to connect the positive clamp (red) to the positive terminal first and then the negative clamp (black) to the negative terminal.

5. Turn On The Charger

Once you are happy that the charger clamps are securely attached to the battery terminals, you can switch the charger on. Once turned on, check for any warning lights upon the charger as this will indicate that there is an issue with how the clamps are connected to the battery. If this is the case, switch off the charger and check the connections again.

how to charge a car battery at home

6. Allow To Fully Charge

As long as there are no warning lights upon the charger, you can leave the charger to work its magic. Depending upon the battery charger you are using will determine whether or not it will turn off once its reached full charge. If it doesn’t, you will need to find out how long it will take and then switch it off manually once it’s reached full charge.

If possible, we strongly recommend investing into a smart car battery charger because they include a range of additional functionality. This can include automatic switch off, float mode, testing and so much more.

7. Reconnect The Car Battery

Once that you are happy that the battery is fully charged, you can proceed to reconnect the battery. We would recommend reconnecting the positive first and negative last in order to avoid giving yourself a shock.

How Long To Charge A Car Battery

If you have a completely dead car battery, it can take 12 to 24 hours to fully charge it with a charge amperage of 4 to 8 amps. However, if you need just enough charge to get the car started, this can take as little as 2 to 4 hours.

Of course, these are just approximate statistics based on charging a regular battery with a standard charger. There are a number of factors that could be considered and may increase the time it takes to charge a car battery.

If you only want to get the car started in order to allow the alternator to charge the battery, we wrote an in-depth guide on how to jump start a car.

Any Potential Problems

Charging your car’s battery is relatively straightforward and there isn’t too much that can go wrong. Most modern chargers come with so many safety features these days and even if you put the clamps on the wrong terminals, the charger would be able to safely deal with it and also alert you with various warnings.

The only thing that we would say is that you will want to locate any PIN codes for your radio. Sometimes disconnecting the battery can clear the settings and require you to input the PIN upon the radio when you start the car.

If you notice that there are warning icons or error messages on the dash, we would recommend using a car diagnostic tool. Similar to the radio PIN issue, the reconnection of the battery can clear settings and the car may have stored the fault code of the battery going flat. If this is the case, simply remove any stored faults codes with the diagnostic tool.

Jump Start vs Charging

There is nothing more frustrating than coming out to your car to find out that the battery is dead. If this is the case, you have the option to either jump start it or use a battery charger.

If you own a car jump starter, you may wish to proceed to jump start the car in order to get it up and running. Alternatively, if you have a running car, you may wish to use that car along with jump leads to jump start your car.

However, if you have the time to do so, we would recommend charging your car’s battery with a charger. The main reason for this is due to the fact that jump starting a car could potentially cause damage to certain electrical components. However, if you correctly jump start a car, the chances of this happening is quite rare but there is still a risk.


If you have a flat battery and want to learn how to charge a car battery yourself, hopefully the above guide has answered all your questions. It’s a relatively straightforward task and very little can go wrong. If you are also in the market for a new charger, we recommend investing into a “smart” charger. The additional safety features provide you with peace of mind and they are also convenient thanks to features such as automatic switch off, float mode and status indicators.

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