How long does it take to charge a car battery?

How long does it take to charge a car battery?

When it comes to charging a car battery, there are several myths and concerns about the issue of overcharging.

The following articles address how to charge a car battery safely.

How many amps is a car battery?

A car’s battery has 48 amperes.

How long does it take to charge a battery?

The time taken to charge a battery depends on the battery condition and the amps of your charger. 

Charging car battery

Charging car battery

If the battery is in good condition

How long does it take to charge a battery at 2 amps?

If the charger capacity is 2 amps per hour, it takes 24 hours (48/2=24) to charge a car battery of 48 amps.

How long does it take to charge a battery at 6 amps?

If the charger capacity is 6 amps per hour, it takes 8 hours (48/6=8) to charge a car battery of 48 amps.

How long does it take to charge a battery at 8 amps?

If the charger capacity is 8 amps per hour, it takes 6 hours (48/8=6) to charge a car battery of 48 amps.

How long does it take to charge a battery at 10 amps?

If the charger capacity is 10 amps per hour, it takes around 5 hours (48/10=4.8) to charge a car battery of 48 amps.

How long does it take to charge a battery at 20 amps?

If the charger capacity is 20 amps per hour, it takes 2.4 hours (48/20=2.4) to charge a car battery of 48 amps.

How long does it take to charge a battery at 50 amps?

If the charger capacity is 50 amps per hour, it takes around 1 hour to charge a car battery of 48 amps.

However, if the battery is dead, using a high-capacity charger like this can damage your battery.

If the battery is out of condition

Before you start charging your battery, you must first know whether your battery is worth charging for.

If your battery is around three years old, it’s better to replace it, as most batteries last no more than four years. 

Further, the climate around you also affects your car’s battery.

For example, if you live in freezing conditions, your battery will have a short life span as car fluid becomes thick during winter, and your car will need more energy from the car’s battery to start.

Also, you must know that if your battery is completely dead, you will need a slower charger to charge it, as a fast charger can damage your battery.

Car battery

Car battery

Risk of overcharging a car battery

  • If the battery gets overcharged overnight, the acid in the cells may result in an explosion, leading to a fire.
  • If not fire explosion, sometimes overcharging causes the battery’s electrolytes to become hot and releases hydrogen and oxygen gas. As the electrolyte evaporates, it exposes the plates, which may corrode.
  • Overcharging puts a lot of stress on the battery. The continuous electric current in the battery generates high heat, which heats the acid in the cells. As a result, the battery may stop working.

How to use a car battery charger

If you think your battery has some life left, you can charge it with a charger.

Car battery charger

Car battery charger

Remove the car battery

Look for the owner’s manual and follow the suggestions to remove the battery, as it varies from vehicle to vehicle.

You may need tools and accessories to remove batteries under the seat or trunk.

However,  in some vehicles, batteries are placed in an accessible place, so you may not need to remove them.

Pick the right types of car battery chargers

Mainly there are three types, serving different purposes.

Charger: a charger always uses a low-amp charge in charging a battery and may take around 24 hours, depending on the output.

Use a portable charger to save yourself from dead batteries on long trips. However, ensure that you do not overcharge the battery.

Maintainer: a maintainer helps to keep your battery going without overcharging it.

If you keep the lights or music on, it will provide continuous energy to the battery.

There are solar-powered maintainers also, which help you to recharge the battery during off-road trails. 

Restorer: Sometimes, the car’s battery builds lead sulfate crystals when it runs on low power. Once the crystals are there, your battery fails to charge fully.

A restorer detects the sulphation level of the battery and uses a desulfation agent to bring back the standard charging capacity of the battery.

It is essential to select a battery charger carefully to ensure a long life for the battery.

1. Some chargers are compatible with all types of batteries. Go for the ones that promise low heat accumulation, avoid explosions, and charge the battery quickly.

2. Some newer chargers have microprocessors to control the battery’s charging, which means these will automatically turn off as soon as the battery is charged.

However, you must be careful with some older models as they need a manual turn-off after the battery is fully charged.

3. Apart from this, digital chargers indicate voltage level, and you can set it as the lowest level.

In some chargers, you can also set the speed of the charging.

Some other chargers show you how much the battery is charged with the gauges present in them, letting you know when you should turn off the charger.

How to charge your car’s battery?

  • Plug in the charger’s positive cable to the battery’s positive terminal.
  • Similarly, plug the negative cable into the negative terminal.
  • Adjust the battery charger to its slowest charging rate.
  • Power on and switch on the timer.
  • Once the battery is charged, switch off the charger first.
  • Now, detach the charger cables from the battery terminals.
Process of connecting to the car battery

Process of connecting to the car battery

Battery chargers not recognizing a battery

It happens mostly when a battery’s voltage drops below the threshold voltage of the charger.

For example, suppose the threshold voltage for a charger is around 8 to 11 volts, and the battery voltage drops below that (happens when the battery remains discharged for a long time).

In that case, the charger does not consider a viable hook-up and does not carry current.

Some chargers will indicate this through continuous flashing while not showing anything.

Also, some charger manufacturers consider charging a battery whose voltage falls below the threshold level a complete waste.

In such cases, you can use a very old or dumb charger to bring some current into the battery to raise its voltage.

Charge the battery with the old charger until it reaches enough voltage (You can check the voltage with a voltmeter. ) to get charged through a smart charger.

Once it reaches the threshold, use a smart charger to charge it completely.

Also, you can connect a second battery to your battery in parallel and with a charger.

Make sure your battery charger recognizes this new battery.

Once the charger has supplied current, disconnect the working battery.

Check the voltage with a voltmeter

Check the voltage with a voltmeter

How to charge a battery without a car battery charger

Use jump cables and a donor vehicle:

Jump leads are electric jumper cables with metal clamps at both ends, and these cables help you to charge the battery under any circumstances.

If you use jumper cables to charge the battery, you will need the help of another vehicle.

  • Firstly, dust off any dust, dirt, or debris from the battery terminals.
  • Put on your protective eye gears.
  • Keep the car engine in OFF condition or neutral mode.
  • Connect the battery’s positive terminal to the other vehicle with a jumper cable.
  • Take a second jumper cable and plug one end into the battery’s negative terminal and the other into the unpainted metal.
  • Wait while your battery is being charged. Generally, it may take 5 minutes.

Use a portable car jump starter:

As the name clears, a jump starter lets you jump-start your vehicle, working as a battery backup.

It is the best option if the battery drains suddenly and towing services cannot help.

  • Firstly, take care of your safety. Remove all the jewelry. Wear all the protective gear like gloves and eyewear.
  • Turn the engine off
  • Connect the charger’s red clam to the battery’s positive terminal.
  • Connect the black clamp, a negative clip, to any unpainted metal piece.
  • Turn on the jump starter after making these connections.
  • Try to start your car. Avoid cranking for more than five seconds. If the engine fails, wait 2-3 minutes, and try again. The engine will start in some time.

Safety tips for using the car battery charger

  • Before you put your battery in charging, ensure that your battery is not broken. 
  • Also, do not remain too close to the battery while charging.
  • Ideally, leaving your battery for the whole night is unsafe, but if you have to do it under unavoidable circumstances, use a slower charger, which avoids heat accumulation. 
  • Further, you must remove any covering on the battery and put it in a cool place to prevent heat-trapping.
  • Do not leave the battery in charging condition for more than 24 hours. Keeping a battery connected to the charger after it is charged is unsafe, even with the newer chargers.


We have described various ways to charge a car battery safely.

Ensure you always get high-quality cables, whether in the charger or the jumper cables.

At Cloom, we manufacture superior-quality cable assemblies catering to our customer’s needs.