How To Charge A Car Battery At Home? Reasons For Charging Failure & FAQs

How To Charge A Car Battery At Home
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How to charge a car battery? Don’t worry! We’ve you covered. In this article, you’ll learn how to do it by various methods. You can do it with jumper cables or a charger.

There are also explanations for why the car battery sometimes fails to charge and some frequently asked questions.

Preparation To Charge A Car Battery

Wear the safety gear

Eyeglasses are necessary to protect you from sparks, falling materials, or battery fluid. You may want to put on gloves to avoid cuts when working with the car. The working area should have good ventilation and lit to help you have better vision.

Children are prohibited around your working area to prevent them from playing with the batteries, chargers, or jumping cables. They can unconsciously mess up and make sparks fly.

Determine the type of battery you’re owing

You can identify the types of your car battery depending on the information written on it. A check on the manufacturer’s website can provide you with sufficient information. There will be figures indicating the voltage of the battery too.

Currently, the two most common types of batteries are VRLA batteries and wet cell batteries. VRLA batteries stand for Valve Regulated Lead-Acid batteries. These batteries require no maintenance during their lifespan. They come as Absorbed Glass Mat batteries and Gel Cell, which are less popular in cars.

The other type is wet cell batteries. You can improve the lifespan and the charge of these batteries.

Take The Suitable Charger

You should consider choosing an appropriate charger for your battery and purposes. Most types of batteries, excluding Gel Cell batteries, can work with most chargers. Many manufacturers released fast chargers to charge the battery quickly and offer a jump start. Besides, you can find trickle chargers, which provide a slower but more lasting charge.

The digital chargers include a microprocessor to control the amount of battery charged. This feature helps to stop the charging process automatically once your battery is full. However, you still need to keep an eye on them while operating to ensure they function properly.

Disconnect And Take Out The Battery

You’d better disconnect the battery before doing any maintenance or repairs on the cars. The process is to disconnect the negative terminal, then continue with the positive one.

If it’s hard to reach the battery or fit the charging cables in the trunk, you can charge the battery without removing it from the vehicle. Otherwise, you should completely remove the battery from your car when charging it.

Polish The Terminals

Grime or dirt staying on the battery terminals can keep the charging cables from building a strong connection to your battery. The dirty terminals may avoid the electricity from flowing smoothly. So, you should clean these terminals carefully.

A wet cloth/sandpaper pad and baking soda are enough to help you clean any rust and grime. After the cleaning, you should ensure the terminals are bare metals to support a strong charge.

Another reminder is not to use bare hands to touch the terminals while white powder is on them. This white powder includes dried sulfuric acid, which can burn your skin.


Methods To Charge A Car Battery

#1: With Jumper Cables

The jumper cables

The jumper cables

The first method to charge a battery is to use jumper cables to create a temporary connection. This process is the best way to charge a car battery because of its fast speed to get your car running again.

With jump cables, you can have two ways to charge your car battery. You can use it either with a running car or without another car. We’ve arranged detailed instructions for each way below to help you charge your car battery.

How to charge a car battery from another car?

Step 1: Park the working car to face your dead car

You should know the batteries’ location in both the working car and your vehicle before parking another car. Usually, the batteries lay in the trunk of the cars.

Please make sure to park the functioning car close to your vehicle enough to connect batteries with jumper cables. Moreover, you should set the brake on both cars to ensure they won’t move during the process.

Step 2: Connect two batteries with the jumper cables

The most important thing to remember is not to touch the negative and positive ends of the cables. This action may ignite sparks that are dangerous for you. You should make sure both cars shut off before connecting the jumper cables.

When progressing with the attachment, you use the jumper cables to connect the positive terminal of the dead battery with the good battery’s positive one.

You should be careful not to make the negative cables dangle in the engine bay. In this area, the negative cables might touch metal to complete a circuit. Hence, you can have an electric shock because of this mistake.

After that, you connect the negative terminal of your dead battery with the good battery’s corresponding terminal. Now, it’s all set to prepare for the next step.

Tips: You should clean both terminals to make a strong connection between the two batteries. Furthermore, it’s important not to mix up the connection between the positive and negative terminals. A wrong terminal connection may result in danger or even a fire.

Step 3: Start the functioning vehicle

As you connected cables securely, you start the functioning car to let its electrical system charge your dead car battery. Please keep the functioning car still during the charging process.

After a minute or two, you should try to start your dead vehicle. If your battery only died recently, it will restart right up. If it doesn’t operate, you should spend a little time charging it.

Step 4: Disconnect the cables and try to run the car

When your dead vehicle starts, it’s time to disconnect the jumper cables from both vehicles. You should let your dead car run for a bit to freshen the engine.

If your car shuts off right after starting for a few minutes, your battery does not have enough electricity to start the car. Another reason for the shutdown may be that the battery is not connected completely to your car.

If the car operates well, you should go for a short drive to thoroughly charge the battery before turning it off. This short drive can help the car’s alternator charge the battery throughout the way.

How to charge a car battery without another car?

Using a mover battery

If you don’t have a functioning car, how to charge your car battery? The great news is you can still charge it without another car. You can have two options to do so.

The first option might be unconventional. The method with a mower battery will work if you use a good mover battery and strong cold-cranking amps.

This charging process is similar to the method with the functioning car and the jumper cables. Here, you change to connect your dead battery’s positive/negative terminals with the corresponding ones with the mower battery using the jumper cables.

Using a portable jumper kit

Besides the mover battery, you can go with a portable jumper kit to charge your dead car battery. This kit includes built-in cables and a battery. If you didn’t own the portable jumper kit, you would refer to the guide to buy one.

You should keep the battery off the kit fully charged before using it to jump-start your dead car. Here, you can follow step-by-step instructions to use the portable jumper kit to charge your car battery.

  1. Bring the portable jumping kit over to your car
  2. Open the hood of your car
  3. Clean off the battery terminals on the battery to ensure there is no corrosion
  4. Get the wires out of the kit
  5. Attach the portable battery to the jumper cables (optional)
  6. Connect the negative terminal of the dead battery to the black clamp, and the positive terminal of the dead battery to the red clamp
  7. Plugin the portable battery box
  8. Wait a minute to let the battery absorb the energy
  9. Start the car (It should start immediately, but if it doesn’t, wait a bit longer and then restart it. Otherwise, it’s too dead that you should replace a new one.)
    • Turn off the portable battery
    • Disconnect the red cable from the battery and disconnect the black cable
    • Leave your car running
    • Give your car a 20-minute drive to recharge the battery

#2: With A Charger

A trickle charger

A trickle charger

Now, let’s explore the method with a charger. This method may take longer than the previous one, but it is a more dependable way. If you don’t use your battery for a while, it’s great to charge it with a charger.

How to charge a car battery with a charger?

Step 1: Put the charge on a steady surface

You should remember not to put the charger directly on the battery because the negative and the positive terminal may connect. This connection may cause damage to both gears (the charger and battery) to start a fire.

The “DO” thing is to place the battery charger on a surface, staying away from the battery. The surface should be stationary and sturdy enough to prevent the charger from falling and disconnecting the process.

You don’t have to worry about the distance between them as the cables will allow them to attach later. You can use cables to separate the charge from the battery.

Step 2: Attach the battery to the charger

Firstly, you connect the negative terminal labeled as the “-” symbol to the black cable with the same symbol. Then you attach the positive terminal with the “+” sign to the red cable.

It’s critical to check the connections before plugging in the charger, as mixing the terminals may lead to a fire or damage to the battery. Also, please make sure you connect the cables to let electricity flow from the charge to your battery.

You should keep in mind that there are letters of POS indicating the positive terminal instead of the “+” sign. Similarly, the negative terminal is labeled as NEG.

Step 3: Set the charger

Different charges can provide different functions for the charging process. For example, digital chargers have displays to demonstrate the remaining battery level in your battery and set the final voltage level. Besides, other battery models let you turn on and off them only.

Speed chargers feature the setting to select the desired speed to charge the battery. Chargers’ brands usually display the fast mode as a rabbit, while the slow mode is a turtle.

The fast chargers are suitable for a battery that recently died because you forget to turn off the lights, for instance. However, the longer dead battery may require a slow charging process to restart before reusing it. You can leave your battery to charge overnight to charge it completely.


  • Do not apply the fast charging method if you can not keep an eye on your battery and leave your car unattended.
  • Suppose you have a charger allowing you to preset the voltage level. In that case, you should know the particular voltage of your battery by finding it in the vehicle’s manual.

Step 4: Check your battery

You should check whether your battery is charging or not after setting the charger. Some digital chargers include a screen to read out the battery’s status, like the capability of holding the charge or the needed replacement for the battery. If your battery is full, the charge will indicate 100% as the sign to inform you.

A voltmeter is useful for you if you want to check the voltage of the charged battery. You can do it by touching the negative and positive cables from the tool to your battery’s corresponding terminals.

Reasons For The Failure Of A Car Battery Charge

The charging process sometimes does not work as you expect. Here are the reasons why the car battery fails to charge.

  • Charging cables don’t connect completely: You should make sure that all the cables attach to the terminals. Otherwise, you may spend more time charging your battery. You should firmly plug in your charger as well.
  • Issues from the battery: The dirt should be wiped away with rust, grime, or corrosion from the terminals before the charging process. Another issue is the aged battery. You can test it by seeing whether it can hold a charge or not. If it can’t, you need to replace it anyway.
  • Issues from your vehicles: Your cars may have issues relating to sensors, bad spark plugs, or else. If you encounter this situation, you need to take your car to the mechanic to repair it.


Is it safe to charge a car battery overnight?

It depends on the chargers you are using. The answer is yes if you use the modern or the automatic chargers. These models can shut down the current once the battery is full. They can reduce the charging current to a trickle when the battery is full to ‘maintain’ the battery.

The nighttime is the best time to charge the battery as you can leave it until morning to have the full battery on the go. Charging the battery overnight can help it last longer as you recharge it at a lower amp.

However, you can’t leave your battery overnight with old fashion chargers. They might overcharge and then damage the battery without manual monitoring.

How to charge a car battery without a charger?

If you don’t have a charger, you can use another method to charge your car battery. A working vehicle and jump cables can help you recharge the battery. Taking your battery to an auto shop is another method you can do too.

How long do car batteries last?

A standard car battery can last up to four years in normal usage. When the batter gets aged, the inside chemical runs out that cannot hold a good charge as the origin. So you need to charge the battery more frequently. If you realize any issues with the battery holding a charge, you should replace the new one.

How to charge a 12-volt battery?

Firstly, you should connect the negative terminal of the 12-volt battery to the charger’s black (negative) cable. Please ensure to use the clamps to connect securely. You can find the negative terminal is labeled “-”. After that, you connect the positive terminal to the red (positive) cable of the battery. You’ll see the “+” mark indicating the positive terminal.

Then leave the battery until it is fully charged. The charger display can reveal the condition of your battery, whether it is full or not. Finally, you disconnect the cables to use them in your car.

How long does it take to charge a car battery?

It can take hours to charge a car battery fully. For example, a 12-volt battery spends from 12 to 24 hours to charge it fully. During the charging process, you should take care of the temperature of the battery. If it gets too hot (e.g., over 125 Fahrenheit), you need to stop charging it for safety.

The Bottom Line

You’ve understood how to charge a car battery by two methods with the jumper cables or with a charger. The process with the jumper cables offers fast charging. You can use them with another functioning car or without them. The other charging method is to use a charger. This way requires more time to charge the battery fully, yet it is more reliable.

You can consider the gears available in your home’s garage to start charging your battery. Don’t forget to share your experience and other tips to charge the car battery at home.

Frank Galvin

Hi everybody! My name is Galvin, an automotive engineer and team leader of Autopartguide. I have a passion and a special love for cars and all auto parts related to them. You can see I'm excited all day with my cars.