How Long Does It Take To Charge A Car Battery

How Long Does It Take To Charge A Car Battery

Having a dead car battery can be extremely frustrating. You walk out to your car, turn the key in the ignition, and instead of the engine roaring to life, you hear nothing but a faint clicking sound. Or maybe the lights and electronics turn on,

but the starter motor doesn’t have enough power to actually crank the engine over. A dead battery leaves you stranded, late for work, or scrambling to find alternate transportation.

The good news is that charging a dead car battery is usually a relatively quick and simple process. However, how long it takes to charge exactly depends on several key factors. In this comprehensive guide, we’ll cover everything you need to know about charging a car battery, including:

  • The basics of how car batteries work
  • Key factors that affect charge times
  • Charging methods and duration
  • Charging tips and precautions
  • Knowing when a battery needs replacement
  • Alternatives to charging a dead battery

How Do Car Batteries Work?

Your vehicle’s battery is a lead-acid battery that produces power through a chemical reaction. Lead plates in the battery are submerged in an electrolyte solution of sulfuric acid and water. When the battery is providing power,

the chemical reaction causes sulfuric acid in the electrolyte to react with the lead plates, producing electrons that create electricity. This electrical current then travels through battery cables to the starter motor and other electronics in your car to power them.

However, as the battery discharges electricity, the sulfuric acid becomes depleted and the chemical reaction slows down. This makes the battery’s charge level drop and its voltage decrease. That’s why over time the battery needs to be recharged by

applying an electrical current from an external charger. This drives the chemical reaction in reverse, re-depositing sulfuric acid back into the electrolyte solution and replenishing the battery’s capacity to hold a charge.

How Do Car Batteries Work?

Key Factors That Affect Charge Times

Battery capacity – Measured in amp hours (Ah) or cold cranking amps (CCA), battery capacity indicates how much charge the battery can hold. The higher the capacity, the longer it takes to fully charge. Parasitic drains – Things like lights or accessories left on during charging can prolong charge times.

  • Battery age – As batteries age and degrade through normal use, their capacity diminishes and charge times increase. Older batteries take longer to charge than newer ones.
  • Battery temperature – Low temperatures slow down the battery’s chemical reactions and ability to accept a charge. Colder batteries take longer to charge.
  • Charger amperage – Chargers with higher amperage provide more power and charge batteries faster than lower amperage models.
  • Charging method – Some charging methods push more electrical current into the battery than others, reducing charge times.
  • Depth of discharge – The deeper a battery is discharged, the longer it takes to recharge. A battery drained to 50% will charge faster than one drained to 10%.

Charge Times by Charging Method

There are three main ways to charge a car battery – jump starting, using a traditional battery charger, and fast charging. Charge duration depends largely on which method you use.

Jump Starting

Jump starting is the quickest way to recharge a dead battery just enough to start the engine. It involves using jumper cables to connect your battery to a good battery in another vehicle. The discharged battery draws current from the good battery to build up enough charge to crank the engine.

A typical dead battery can usually be jump started in 3-5 minutes this way. However, this only provides a surface charge, so the battery will still need further charging to fully replenish it.

Traditional Battery Charger

The most common way to charge a dead car battery is with a traditional battery charger. These units plug into a wall outlet and supply a low electrical current to the battery over several hours.

Charge times with traditional chargers vary based on charger amperage and battery capacity:

  • 2 amp charger: Charges a standard 50Ah battery in about 24 hours
  • 10 amp charger: Charges a standard 50Ah battery in about 5 hours
  • 15 amp charger: Charges a standard 50Ah battery in about 3 hours

Higher capacity and deeply discharged batteries take longer. For example, a large 85Ah battery drained to 10% could take a 2 amp charger 48 hours for a full charge.

Batteries also charge faster in the beginning and slower as they near a full charge. The final topping off can take a disproportionately long time compared to the initial charging.

Fast Battery Charger

For quicker charging, some higher amperage chargers can fully charge a dead battery in 1-2 hours. These fast chargers work best when time is limited and you need to get back on the road quickly.

Just be careful using them frequently, as the intense power they supply can shorten overall battery life if overused. But for occasional use, they provide a handy way to drastically cut charge times.

Charge Times By Charging Method
Charge Times by Charging Method

Charge Times Based on Key Factors

Based on the factors that affect charge times outlined previously, here are some general guidelines for how long to expect a battery to take to charge in certain situations:

A new 50Ah battery will charge faster than an old one with 30Ah capacity remaining. Charging a battery at 5°F will take longer than charging one at 70°F. A battery drained to 20% will charge faster than one drained to 5%.

Charging a battery in a car with the headlights left on will take longer than charging one with everything off. Using a 10 amp charger will charge a battery faster than a 2 amp model. Leaving a battery on the charger for an extra few hours after it’s fully charged can help ensure maximum capacity.

Tips for Faster Charging

Here are some useful tips to help reduce car battery charge times:

  • Use the fastest, highest amperage charger available – 10 amps or above if possible. Make sure the battery is at room temperature if possible, not freezing cold.
  • Disable or disconnect any accessories that could be slowly draining the battery. Check the battery’s age – newer batteries charge faster than those over 3-5 years old.
  • Charge in shorter bursts with breaks in between to avoid overheating rather than charging continuously. Consider a jump start first to get some charge in before using a charger.
  • Don’t interrupt the charging process once started until fully charged. Let the battery rest 30-60 minutes after full charge before reinstalling.
Tips For Faster Charging
Tips for Faster Charging

Precautions When Charging

Wear eye protection and avoid touching your eyes while working near batteries. Have plenty of ventilation to avoid inhaling hazardous fumes. Make sure to attach charger clamps to the proper battery terminals. Disconnect the battery if it overheats, bulges, leaks or spews acid. Replace it.

Keep sparks, flames, and cigarettes away as hydrogen gas from charging is flammable. Only charge lead-acid or lithium-ion car batteries, not dry cell or NiCad batteries. Don’t charge a frozen battery – allow it to warm up first.

Avoid charger sparks on the battery by attaching clamps first before plugging in. Use a timer to avoid overcharging, which can damage batteries. Check electrolyte levels and refill battery cells with distilled water as needed before charging.

Knowing When It’s Time for a New Battery

Sometimes car batteries that have aged or been deeply discharged multiple times never fully bounce back despite lengthy charging. No matter how long they charge, they quickly drain again or lack the power to crank the engine.

Signs that a car battery needs replacing rather than just recharging include:

  • Failure to hold a charge for more than a day or two
  • Inability to start the car even after extended charging
  • Cracked case or leaking battery acid
  • Corroded battery terminals
  • White powdery deposits on terminals
  • Bloated or bulging battery case
  • Excessively long charging times measured in days

If your battery is more than 3-5 years old, replacement may be the wise option compared to sinking more time and effort into trying to recharge a dying battery.

Knowing When It's Time For A New Battery
Knowing When It’s Time for a New Battery

Alternatives to Charging a Dead Battery

Jump starts – Many auto parts stores, dealerships, repair shops, and roadside assistance services can provide a jump start to get you up and running quickly. This is convenient but only a temporary fix.

Mobile battery replacement – Services like Mobile Battery Replacement will come to your location and install a fully charged replacement battery so you can drive again right away. They recycle the old dead battery.

  • Towing – You can have the vehicle towed to a repair shop or dealership to have the battery tested, charged, or replaced. This avoids having to charge it yourself.
  • Rental car – For longer repairs, you can rent a car for a day or two to keep your transportation needs covered.
  • Rideshares – Use a rideshare service like Uber or Lyft to get where you need to go while your battery is being addressed.
  • Public transportation – Buses, subways, and trains can provide transportation in a pinch if you’re unable to charge your battery promptly.

How to tell if your battery needs replacement

Have the battery tested. Many auto parts stores will test your battery’s charging capacity for free. If it’s below 50-75% of new battery capacity, it likely needs replacement. Check the manufacture date code. Batteries typically last 3-5 years. If yours is over 5 years old, plan for a replacement.

Look for visible damage like cracks, leaks, bulges, corrosion. These signs indicate it’s time for a new battery. Use a battery load tester. This device draws current from the battery to simulate engine load. Weak batteries will show voltage drop indicating replacement.

Notice slow cranking when trying to start. As plates sulfate, cranking speed and power decreases.

How to tell if your battery needs replacement

Steps to maximize battery life:

Clean battery terminals regularly with a wire brush to remove corrosion. Make sure battery cables are tight and free of fraying. Replace damaged cables. Avoid deeply discharging. Frequent deep discharges shorten battery life. Don’t leave doors or trunk open with lights on, draining the battery.

Consider a battery tender to maintain charge if the car sits unused for weeks. Drive regularly or take short drives to recharge if the car sits for extended periods. Have the charging system tested annually. Weak alternators don’t fully recharge.

Replace when capacity drops below 80% to avoid being stranded with a dead battery.

FAQs(Frequent Asked Question)

How long does a dead car battery take to charge?
A dead car battery can typically be fully recharged in 3-6 hours using a 10-amp battery charger. Larger or heavily depleted batteries may need 24 hours or more to reach a full charge. The charge time depends on the charger amperage, battery capacity, age, and level of discharge.

Can a completely dead battery be recharged?
Yes, even a totally dead battery that won’t crank the engine can usually be recovered by recharging. However, batteries drained below 10% for extended periods may have permanent damage. Recharge any dead battery promptly before sulfation prevents accepting a charge.

How do I know when my car battery is fully charged?
A battery is fully charged when 1) the charger indicates completion, 2) voltage reads 12.6-12.8 volts with the car off, and 3) voltage holds steady above 13 volts with the car running. A load tester showing 95% capacity also indicates full charge.

How long does it take to charge a 12 volt battery?
A typical 12 volt, 50 amp-hour car battery will require 2-6 hours to fully charge from a depleted state depending on the charger’s amperage. Lower capacity 12 volt batteries may charge in under 2 hours, while larger ones could take 10 hours or more.

What kind of charger do you use for a car battery?
You should use a compatible lead-acid battery charger with at least 10 amps for a standard car battery. Larger batteries may need higher amperage ratings. Select an automatic charger that switches to a maintenance mode when full.

Are car battery chargers a good idea?
Yes, a dedicated automatic car battery charger is extremely useful for recharging dead batteries without needing a second vehicle or removing the battery. They are safer and more efficient than manual methods and provide optimal charging current.


In conclusion, reviving a dead car battery is usually a straightforward process if you understand what factors affect charge times. The battery’s capacity, age, temperature, and depth of discharge along with the amperage of the charger all influence how long it takes to reach a full charge.

Traditional chargers may require several hours to recharge a depleted battery while high-amperage fast chargers can do it in under two hours in a pinch. It’s important to use the right type of charger and exercise safety precautions during charging.

With some basic knowledge and preparation, you can minimize downtime and get your car up and running again quickly when faced with a dead battery. If the battery is too old or damaged to hold a charge, replacement is the best option. And if you don’t have the capability to charge it yourself,

services like mobile battery replacement or towing to a shop can get you back on the road. Understanding your options for safely charging or replacing a dead battery ensures you aren’t left stranded with a vehicle that won’t start.

Related posts

Leave a Comment