How to Efficiently Charge a Car Battery (5 Steps DIY)

Car Battery Charger

Your car battery stands between you and the places you want to go. When it is running right, there’s nothing holding you back. When it dies, it becomes very difficult to get the car started. That’s why it’s important to know how to efficiently charge a car battery.

We review the steps you need to charge a car battery and discuss what to do if it won’t hold a charge.

How to Charge a Car Battery

Charging a car battery may sound like a straightforward job. However, to do it properly, you need some knowledge. Here is how to charge your car battery safely. Remember always to use eye and skin protection when you are working with car batteries.

  1. Turn Everything Off

    Car Light Switch On

    Before you get started, it’s vital that you shut everything off on the car. This includes the electrical features, as well as the exterior and interior lights. If you leave these items on, the battery could drain while you are charging it.
    Some car models also require you to remove the battery terminals before charging the battery not to damage electrical parts. Check your repair manual for your specific car model to be sure.
    If you need to test your battery moving on, use a voltmeter. Touch the prongs to the appropriate battery terminals to get a reading. 12.4 to 12.7 volts says that your 12-volt car battery is charged. Anything lower than 12 volts indicates low voltage, leaving you with a battery that might not start the engine.

  2. Set Charge Rate

    Battery Charge Rate E1619977088430

    On your charger, you want to set the charge rate before you connect it to the battery. If you have a very basic battery charger, you might not have these options. Typically, the charge rate ranges from 2 to 10 amps.
    In most cases, you want to charge your battery on the lowest setting. By doing a slow charge, you ensure the battery remains in good condition. It also keeps you from overcharging the battery. The only time you should use a fast-charge setting is if you need the battery right away. While this will get you back on the road quickly, it will reduce the battery’s life significantly.

  3. Clean Battery Terminals

    Corrosion Battery Terminal

    Locate the positive and negative battery terminals. Take off the plastic cover from the positive terminal and clean any corrosion off with a wire brush. 
    If you are unable to remove the corrosion with the brush, consider using a baking soda paste instead. By cleaning off the battery, you ensure that the charger makes a good connection. 

  4. Connect Your Charger

    Best Car Battery Chargers

    Put your battery charger in a close location where it is secure. Connect the clamp containing the red cable with the positive terminal on the battery. Make sure it is connected and isn’t going to fall off.
    Next, you will do the same with the black cable and the negative battery terminal. Once the charger is connected, you can turn it on. 

  5. Charge & Test Battery

    Start Engine

    Allow the battery charger to stay connected until a full charge is achieved. Sometimes, this will take overnight. Once the battery is charged, remove the clips in the opposite order that you put them on.
    Replace the cap on the terminal and attempt to start your vehicle. If everything works well, you won’t need to worry about the battery. However, if the battery doesn’t work, you might need a replacement. 

What Does a Car Battery Do?

Why is the car battery important and why should you ensure it is always charged? First, the car battery ensures the motor can turn over and start. When you put your key in the ignition, the battery is responsible for delivering the voltage needed to activate the starter. 

Additionally, the automotive battery provides voltage to the engine while it is running and powers up your important accessories. Without it, you wouldn’t have headlights, a car radio or anything else electronic in the vehicle. 

How Long to Charge a Car Battery

Determining how long it will take to charge a battery relies on several factors. First, it will depend on what type of charger you are using. Additionally, it depends on how dead the battery is. 

Charging an automotive battery fully can take a couple of hours or a few days. Using a partially charged battery is possible, but you run the chance of getting stranded somewhere, waiting for a jump start.

If you do need to jump start your vehicle, make sure you leave the engine running afterward. It’s best to take a drive and let the alternator charge the battery before shutting it down. If you turn off the engine too quickly after a jump start, you might find yourself stranded all over again. 

If the battery is completely dead, it’s possible that the jump start won’t work. Even if you leave it hooked up to a car charger, you will notice that nothing happens.

What to Do If a Car Battery Won’t Hold a Charge

If your battery isn’t holding a charge, you will need to get a replacement. Before having it towed to your local automotive shop, try a new battery. If you face the same problems after replacing the battery, it could be possible that isn’t your problem at all. In fact, many people replace the car battery only to find out that the alternator was defective, leaving the battery with no way to charge.

Written by: Magnus Sellén

Founder, owner & main author of Mechanic Base. I have been repairing cars for more than 10 years, specialized in advanced diagnostics & troubleshooting. I have also been a drifting driver and mechanic for over 7 years.