How to Charge a Car Battery?

Sooner or later, most drivers encounter the inevitable inconvenience of a dead car battery. You don’t have to be an experienced auto mechanic to know that your car won’t start at all without a running battery. In this situation, you need to call roadside assistance or find a way to take your vehicle to a workshop. Both options are far from ideal.

Alternatively, you have the option of avoiding these choices and charging your car battery yourself. As long as you have the right gear like a portable battery charger, you can perform this task anywhere you need it, even if you’re stuck on the side of the road.

Let’s break down how to charge a car battery.

What Does a Car Battery Do?

Before we charge ahead, you should know what a car battery does. It serves two purposes:

First, the battery delivers voltage to the starter by transforming chemical energy into electrical energy.

Second, it keeps your car running. The car battery delivers a constant voltage current to keep your engine and accessories (like your radio, headlights, and all onboard computers) running.

If your battery is too weak or too old, it cannot do both. You may need to charge your car battery if your engine starts sluggishly or slowly, or if your battery is completely dead.

Beyond starting your car, charging your battery can help you determine whether or not it’s time for a new one. For example, leaving an interior light on overnight will drain your battery, but if the battery is “healthy” it should recharge quickly. However, a battery that needs to be replaced will not hold a charge or will need to be charged multiple times.

Related Post: 7 Things That Can Drain Your Car Battery

How to Charge a Car Battery?

Let’s break down how to charge a car battery.

#1. Prepare the Battery

Let’s see what we’re working with: While most vehicles don’t require battery removal, some car batteries must be lifted out of their holding trays. If your battery needs to be removed, now is the time to do so.

#2. Turn Off All Electronics

Once your battery is prepared for charging (if necessary), make sure that all electronics in your car are powered down, including any accessories such as the interior cabin light or the stereo. If any electronics remain powered on during charging, the battery may experience an electrical arc during the process. Again, make sure all power and electronics have been turned off!

#3. Remove The negative Cable First, Then the Positive

  • The negative cable is almost always a black cable marked with a “-” symbol on the terminal.
  • The positive cable is almost always a red cable marked with a “+” symbol on the terminal.

If your battery has plastic caps over the terminals, pry them free to remove the cables. Then carefully loosen the negative cable and pull it away from the battery. Place the negative cable far from the positive cable to prevent a charge from transferring between the two sources (trust us on this one). Repeat the process for the positive cable and terminal.

#4. Clean The Battery Terminals

Before you start charging your battery, it’s a good idea to clean your terminals. You can do so using a terminal cleaning brush, which looks similar to a small toothbrush and is used to clear away corrosive debris and dirt from the terminals. You can also use either a commercial battery cleaning solution or make your own by mixing baking soda and water.

Cleaning the terminals neutralizes battery acid and prevents malfunctions from occurring when you charge the battery and reconnect the terminals.

When cleaning your battery’s terminals, always make sure you wear face and eye protection for safety.

Related Post: How to Clean Battery Terminals

#5. Connect the Car Battery Charger

NOTE: Your charger may have specific instructions for its operation, so you should always follow those instructions if they contradict these guidelines.

First, make sure the car battery charger is powered off. Then, hook the positive cable on the charger up to the positive terminal on the battery. Repeat the process for the negative cable. Do not reverse these steps, the positive cable has got to be connected first.

Charge Car Battery

With both cables connected, it’s time to turn your charger on. Begin by setting it to the lowest rate by default. If your charger has a timer, set it for the appropriate charge time.

Note: For information on how long it takes to charge your car’s battery, check your owner’s manual or search online for your vehicle’s specific timing needs.

#6. Remove The Charger After Charging Is Complete

After the battery has regained its car-starting powers, turn off and if needed, unplug the charger from its power source. Time to detach the clamps! It may sound counterintuitive, but this should be done in reverse order—the negative (black) clamp should be the first one you remove, followed by the positive (red) clamp.

If your battery was removed during step 1, set it back into the tray and install the hold-down clamp(s). Replace the cables on the terminals for your car battery by reconnecting the positive cable before replacing the negative.

When to Use a Battery Charger?

When to use a battery charger:

  • If you left the lights on in your car overnight, charge your battery and it should continue to perform as expected.
  • If your headlights or radio have been on for a long period of time without turning on the car, you should charge the battery.
  • If your vehicle has been sitting for a long period of time, the battery may be dead and can be fully fixed with a simple charge.

When not to use a battery charger:

  • If your car suddenly won’t start, it may mean that you have an old battery or a more serious vehicle problem.
  • If you have a problem with your car’s alternator or charging system, these issues need to be addressed before charging the battery.

How long does it take to charge a car battery?

This depends on the amount of amperage the battery charger will output. On the low end, most range from one to three amps (often called a trickle charge) and top out between eight to twelve amps. Other battery chargers output higher amperage, but that amount can overwhelm your vehicle’s battery.

If the battery voltage is below 11.85 and your charger is putting out a 5-amp charge rate, it will take about 12 hours to fully charge a battery with 400 to 500 cold-cranking amps. The same battery will take about 6 hours to fully charge if the charge rate is 10 amps.

The lower the open-circuit voltage in the battery and the more cold-cranking amps, the longer it will take to charge the battery.

How do you charge a completely dead battery?


What is the proper way to charge a car battery?

How to Charge a Car Battery: step by step
1. Prepare the battery.
2. Turn off all electronics.
3. Remove the negative cable first, then positive.
4. Clean the battery terminals.
5. Connect the car battery charger.
6. Remove the charger after charging is complete.

Is there a way to charge a dead car battery?

All you need is a battery charger and an outlet. Locate your vehicle’s battery terminals, verify your charger is unplugged and off, attach the charger to the battery, plug it in and turn it on, set the correct settings, and you’re good to go!

How long does a car battery take to charge?

About 10-24 hours, depending on how weak your battery is. If you’re using a trickle charger, expect it to take days. Don’t expect an under-charged battery to do the job of a fully charged one. Take your battery off the charger early, and you may risk needing a jump-start later.

How long should you leave your car running to charge the battery?

If you have jump-started your car, it is recommended to let your vehicle run for at least 30 minutes because it would typically require at least half an hour to charge a dead battery entirely or at least sufficiently.

Should I charge my car battery at 2 amps or 10 amps?

Lower Amp settings will take longer to charge your battery, but they can help extend its lifespan. If you have a lead-acid battery, a 2-amp charger is better. If you have a lithium-ion battery, a 10-amp charger is recommended.