How to use a Car Battery Charger

We’ve all been there. It’s morning, and you go to start the car, but it just won’t start. Cue a few strong words.

A flat or depleted car battery can happen for a number of reasons. Whether it’s for maintenance, because you’ve left your lights on overnight and drained the battery, or the battery has degraded over time, there are plenty of reasons your battery has died.

Keep reading to learn how to use a car battery charger to bring your vehicle back to life.

What type of charger do I need?

Depending on the type of vehicle you have and what you’re using it for, you may need to use a variety of chargers. To break it down simply, there are two types of car battery chargers:

1. Standard charger

A traditional car battery charger, or linear charger, can be used on most cars and has limited features.

Standard chargers charge your vehicle by continuously delivering electricity to your battery. Over time, this may damage your battery health. Please note that these chargers are generally not suitable for vehicles with start-stop technology.

2. Intelligent/smart chargers

Intelligent (or smart chargers) are more modern and have various settings and features that can help to maintain battery health.

For example, trickle charging can feed charge into your battery very slowly when a vehicle is out of action for a while, or multi-stage charging can help maintain battery health.

How to use a car battery charger

How you charge a car battery will vary depending on whether you want to get a flat battery started, charge a waning battery, or maintain health during storage. If unsure, contact a professional mechanic before you tinker under the bonnet!

What you need to charge a car battery

Be prepared for the job! Here’s what you need to charge your battery.

• Extension cord (if needed)

• Battery charger

• Screwdriver (for battery cover removal - if needed)

• Torch (for a clearer view at night)

How to use car battery charger at home

Want to breathe new life into your car? Here’s a quick overview of how to use a car battery charger at home:

• Double-check what battery your car uses — Not all cars have the same battery. Cars with start-stop technology have AGM or EFB batteries. Your car manual will have this information, but you can also ask a local garage.

• Read your car charging manual — This will help you understand how to use the charger and work out how long to charge your battery. The time will vary depending on the type of battery and engine size, although you can expect anywhere between 10 and 24 hours to fully charge a battery.

• Disconnect the battery — While you can charge a car with a connected battery, it’s best to disconnect the battery and clean it first. Disconnect the negative (black) lead first and reconnect it last, or you could get an electric shock.

• Connect the charger — Next, connect the charger by connecting the charger clamps to the battery terminal. Match positive to positive and negative to negative. Never leave the charger on top of the battery while charging, and keep the charger as far from the battery as possible.

• Turn on the charger — Let the battery charge. Some chargers will automatically turn off when charging is complete, but some might need to be disconnected. Read the manual and find out how long a charge takes so you can disconnect at the right time.

• Complete! — When charged, unplug the charger and disconnect the clamps. You can reconnect the car battery (remember, positive first and negative last!), and you’re done. An indicator will show you when charging is complete if you're using a smart charger.

How to use a battery charger while driving

Alongside charging your car when it’s stationary, you can charge your battery by driving. Of course, this won’t work if your battery is completely dead. But if your car is idle for long periods, you can drive it to keep the battery topped up.

Most cars require around 30 minutes of motorway driving to recharge fully. If your vehicle hasn’t been driven for a long time, it might take more than 30 minutes. So, make more than a quick trip to the shops to keep your battery healthy.

Can I charge a car battery without a charger?

Technically, your car is supposed to charge itself with a part called an alternator. The alternator is a magnetic coil that’s powered by the engine. It generates current that goes back into the battery and charges as you drive. Faulty alternators are the most common cause of a dead battery.

How to use car battery charger - Extra tips to know

Take a note of these extra tips before making that all-important car battery charger connection.

• Batteries can give off hydrogen gas when charged, so keep the charger away from the battery and leave the top of the battery clear.

• Batteries don’t last forever. If your charge drops regularly, it might need to be replaced.

• Care and maintenance can help your battery stay healthy and save you money in the long-term.

• If you have a voltmeter, before charging, you can use it to see how much charge your battery currently has. This is especially important if you’re using an older charger with limited features that do not turn off automatically.

• You should charge your battery at a low level if you have time (under ten amps) to help maintain your car battery health over the long term, although always check your manual for best practice instructions.

How to maintain a healthy car battery

If you want to avoid any battery scares, you can help maintain a healthy battery by:

1. Cleaning your car battery

Get rid of any dirt or grime before it has a chance to get into your battery cells and cause damage.

2. Maintain during downtime

If you have a vehicle that is rarely used or has a long layoff, make sure you regularly charge the battery to avoid it becoming depleted and damaged.

3. Avoid over-charging

Over-charging can cause damage to your battery. To avoid this, make sure you charge at a low level and unplug your charger when it’s done.

4. Replace when required

Generally, car batteries can perform at a good level for 4 years, so you should replace yours at that frequency.

Final thoughts on how to use a car battery charger

A flat battery is nothing short of annoying. But luckily, this is an easy fix! Hopefully, this blog has helped you recharge your car battery without muss or fuss. Bookmark the page so you can return when it’s time to boost your battery.

Do you need a service to check on battery health, or do you need a full replacement? Use our garage search feature and pay for your repairs or parts in easy-to-manage monthly car repairs.

Author - Joseph Law

Joseph has been writing about cars for over seven years and writing for Bumper for over two, blending his passion for automobiles with a talent for storytelling.

Joseph has written about engineering and cars for Autozilla, Komaspec, and several engineering manufacturers. When he's not writing or tinkering with one of his five cars, Joseph dreams of owning an Alfa Romeo 33 Stradale.