How Long Does it Takes to Charge a Dead Car Battery?
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How Long Does it Takes to Charge a Dead Car Battery?

By Jason Collins | September 22, 2021

A completely discharged car battery can take up to twelve hours to recharge, sometimes longer, depending on the type of battery you have.

Nobody wants to jump into their car, and upon trying to start the ignition, you get no response from the engine. The good news is that if it's a dead car battery, there are several options to charge it up again.

We know time is of the essence, and you are already wondering how long does it take to charge a car battery? Unfortunately, the further discharged a battery is, the longer the charging time to reach full charge again.

Let's look at how long it takes to charge a car battery and what options you have available to recharge it properly.

Why Your Battery Needs a Boost

It is not always the case that your dead battery needs replacement; sometimes it just needs a boost.

There are several reasons why your battery may need recharging, including:

  • You left the headlights or interior lights on for a long period of time.
  • You may have a faulty alternator.
  • Extreme temperatures can have a negative effect. Freezing cold weather can prevent your battery from working correctly, just as scorching hot weather can.
  • You could be excessively starting your car.
  • The battery may be too old.

Types of Battery Chargers

Depending on what type of charger you use for recharging your car battery and the type of battery your car has, the charging time varies greatly until full charge is reached.

Below are the different types of chargers available.

Linear Charger: The linear charger is the most straightforward car battery charger available. It charges the battery through a wall socket and is a plug-in charger. While it may be the simplest way, it isn't the fastest. A linear charger requires minimal set-up and power; however, it has a slow charging rate since it operates at low amperage.

A linear battery charger can take up to twelve hours to fully recharge a 12-volt lead-acid battery. This charging option charges on a continuous charge, which means it does not have a controller to stop charging the battery once it's full. Overcharging occurs if you don't carefully monitor the charging levels and can result in overheating and shorten your car's battery life. Overcharging can also cause a car's battery to fail or even explode.

Multi-stage Charger: A multi-stage charger carries a higher price tag compared to a linear charger. It may be more expensive, but the risk for overcharging is lower because it recharges the battery in bursts instead of continuously. There is less chance of long-term damage with a multi-stage charger.

Multi-stage battery chargers are also known as intelligent chargers because of their staged charging method at higher amperes.

This type of battery charger encourages fast charging and can go up to 50 amperes, which charges a battery in less than one hour.

Trickle Charger: Trickle chargers operate between an amperage of 0.8 and 4. They shouldn't charge a dead battery because they operate on a low power output level. A trickle charger prevents low battery charge if you connect it to the battery while the car isn't in use.

Trickle chargers are commonly used for charging AGM batteries because they shouldn't charge too quickly. Most manufacturers advise that AGM batteries should not be charged in less than five hours.

How Long Does It Take To Trickle Charge A Car Battery?

Trickle chargers can take upwards of two days to fully charge a battery. Trickle charging is beneficial for the life of your battery since it won't lead to overcharging the battery accidentally. However, it is a slow process since a trickle charger only uses 1-2 amps.

To determine how much time you need to trickle charge your car's battery, you should either read your car's spec sheet or use a battery tester to see how much battery is left.

If you do not own a battery tester, then you can calculate the time using the:

  • Minutes left in your battery
  • Reserve capacity in terms of amp-hours
  • Voltage used
  • Current battery percentage

How Long Does it Take to Charge a Car Battery Using a 12-Volt Charger?

The answer to the above question depends on the number of amps you are using for battery charging.

For instance:

  • 40-Amp Charger: 40 amps has a fast-charging capacity and can charge a car's battery within a few minutes to an hour.
  • 2-Amp Charger: A battery charger with low amp charging, such as 2 amps, can recharge a battery in one to two days. This is because a 2-amp battery provides only 1 ampere per hour.
  • 4-Amp Charger: Generally, a car battery holds 48 amps, so using this amount of voltage will take up to twelve hours to reach full battery capacity.
  • 10-Amp Charger: A 10-amp charger can recharge a half-discharged small car battery within 2-3 hours and a medium-size car battery within 3-4 hours. A large car battery at 50% charge capacity takes 4-7 hours to reach full charge.

How Long Does it Take to Charge a Car Battery While Driving?

While we would love to answer the question above with an exact number of hours, it depends on certain factors. How long it takes to charge a car battery while driving depends on the car usage cycle and initial charge time.

Car Usage Cycle

If you leave your car stationary and unused for long periods, then your car's battery is more prone to dying. The same applies if you leave your car's lights or air conditioning on for long periods.

The best way to charge your car's battery is while it's idling. Idling is a self-help for the vehicle and partially recharges the battery if the alternator isn't faulty or damaged. If idling doesn't help, you can take your car for a short drive to help recharge the battery to full capacity.

Initial Charge Time

The amount of charging time needed for a car's battery to reach full charge depends on several factors, including:

  • When last your battery was fully charged
  • The make and model of the car
  • The age/model year of the vehicle
  • Previous usage
  • The type of battery

So, how long, on average, does it take to charge a car battery while driving? When driving on high-speed lanes, you could typically charge your battery within 30 minutes. However, if you are driving in slower-moving lanes or in traffic, it could take up to an hour or possibly longer. Don't use your air conditioning or electronic devices while driving; this increases the charging time.

How Long Does It Take To Jump Start A Car Battery?

If your car has died completely and you need to get it to a mechanic, then jump-starting the battery may be the only way to charge it and get it started again. Jump-starting your car is the best solution for a temporary fix.

It takes about 5 minutes to connect the jumper cables to the battery terminals and recharge the battery. As a rule of thumb, it is always a good idea to wait about 2 minutes after jump-starting the car to let it idle a bit and allow the power to flow through.

A jump-started car can usually run for about 10-15 minutes, but limit your driving time if you want to avoid damage to the alternator.

If you are caught on the side of the road with a dead battery, then contact roadside assistance for help jump-starting your vehicle again.

How Long Does it Take to Charge a Car Battery in Electric Cars?

Again, there isn't a standard answer to how long it takes to charge an electric vehicle's battery. Several variables impact the charging time of a battery of an electric car. The two primary factors are the power source and the vehicle charging capacity.

Electric cars, such as the Tesla Model 3, accompany a common misconception that the "thing" you plug in is the charger. In fact, there is a battery charger inside the electric vehicle that converts the alternating current from the wall into a direct current to charge the battery.

To estimate the charging time of an electric car's battery, you divide the battery capacity's kWh number by the onboard charger's power rating, then add 10 percent to the losses associated with charging.