How Long Does it Take to Charge a Car Battery?

Often when you need to charge a car battery, you are in hurry and need to do it fast. Here are the average charging times for car batteries

How Long Does It Take To Charge A Car Battery

You are in a hurry on the way to work, and you jump into your car and quickly turn the key – Nothing happens.

The car battery is drained. You have a car battery charger in your garage, but how long does it take to charge a car battery?

Charging a car battery is not always as easy as it sounds; there are several tricks out there to save your battery and give it a longer lifetime!

In this article, you will get all the answers you want for this question, and a bit more!

How Long Does It Take to Charge a Dead Car Battery

Generally, it will take 2 to 4 hours to fully charge a car battery with a 20 Amp battery charger and 12 to 24 hours with a 4 Amp charger. The charging time heavily depends on the car battery and the charger’s power output.

The most common rate for car battery chargers is around 4 amps. To fully charge a battery of the size 52 Ah would take about 10 hours from dead to fully loaded, but you could probably start your car within 1 hour.

First, you have to look at your car battery charger to find out how much ampere it’s giving out. High amperes charge your car battery faster. Low ampere is better for maintenance charging of your battery over long periods.

You also have to look at the size of your car battery and the battery type. Usually, a mid-sized car uses a battery of the size 40-80Ah. You also have to take in mind the kind of car battery. An AGM/GEL battery can charge up a bit faster than a regular wet battery.

Charging times with different battery chargers

Different car battery chargers give different amounts of power, so the charging time of a car battery will depend a lot on this. For sure, it takes a different amount of time to charge different types and sizes of batteries also, but there are times for a normal-sized car battery around 62 Ah.

Here is how long it takes to charge a car battery:

  • 2 Amp charger: 24 to 48 hours
  • 4 Amp charger: 12 to 24 hours
  • 10 Amp charger: 3 to 6 hours
  • 20 Amp charger: 2 to 4 hours
  • 40 Amp charger: 30 minuter to 1 hour

What is the best speed to charge a car battery?

Charging Car Battery

The speed of your car battery charging should depend on what you want to acquire. Fast charging can damage your battery and will make its life shorter. Long-time charging with low amps is the best for keeping the battery’s lifetime long.

Usually, a standard car battery charger is giving out 4-15 amperes. 2-4 ampere is typical for maintenance charging, and it will take around 24 hours to fully charge a dead battery at this load. Check your car battery charger for any settings for the charging rate and apply the charging rate for your needs.

To charge your car battery quickly, without damaging your car battery, I would recommend charging your battery at the rate of 8-15 amperes. Charging your battery over 15 amperes can damage your battery if you are unlucky and make the lifetime shorter.

What causes a battery to go flat?

There could be many reasons why your car battery went flat. The most common reason is that you forgot a light or something similar in the car before leaving it. It can also be a problem with some electrical consumer that does not want to switch off when you turn off the ignition.

Also, a bad car battery can cause your battery to drain. To learn more about the different causes, you can see out an article about the main reasons why your car battery is flat.

How long does a car have to run to charge a dead battery?

If you jump-start, you can also let your car’s alternator charge the car battery for you. How long it will take for your car to charge the battery depends a lot on the car engine and the size of the car battery. Cars have very different effects on the alternators, giving everything from 30 to 150 amperes.

The engine’s RPM also matters when charging a car battery because the alternator is charging harder when it is spinning faster. If you want to charge your car battery fully with your alternator, you can expect it to take some hours.

It is always recommended to charge your dead car battery with a car battery charger instead of the engine though.

Which car battery charger is best to use?

Charge Car Battery

First, you have to figure out what type of battery charger you need. Maybe you need a fast one or just a maintenance charger?

Modern chargers are easy to connect and have battery charging monitoring, which will regulate the amps themselves. But anyways check to see how many amps it’s charging with before buying one.

Cheaper chargers do often promise more amps than they charge with. It’s better to choose a quality charger that gives lower amps instead. It will save your car battery, and it will minimize the risk of damage to your vehicle.

A car battery charger I really can recommend is the CTEK chargers. You can find them here on our list of “Best Car Battery Chargers.” They have several sizes of their chargers for your needs, and it’s a well-known brand probably making the best car battery chargers on the market.

Written by:

Magnus is the owner and main author of MechanicBase. He has been working as a mechanic for over 10 years, and the majority of them specialized in advanced diagnostics and troubleshooting. Certified Automotive Diagnostic Technician.