How Long Does It Take Alternator To Charge Battery? (Read)

When starting your vehicle, you are also charging its battery. Therefore, let your car run for a few minutes to help charge its battery upon starting your engine. 

How does it take an alternator to charge your battery? An alternator can give up to 80 amps. It gives your car the capacity to charge your flat battery to 80 percent complete in 2 hours. 

As long as your alternator can manage to produce 14 volts in your battery terminals this whole time while driving, it will be at full charge in no time.

How Long Does It Take Alternator To Charge Battery

How Long Does It Take The Alternator To Charge The Battery?

To start the alternator to charge the battery, it will just take 30 minutes to start and 2 hours to get your flat battery to 80 percent complete. 

While Idling

How long should you Idle your car to charge its battery? Idling your car to charge the battery is not recommended. However, if you have an older version car, idling to charge the battery is okay. 

You can idle your car for 15-20 minutes, it is enough to give your car battery enough charge to restart its own, but it is not great to do this process for newer version cars. 

If you are curious if your alternator charges your car’s battery while idling, the answer is yes. Regardless, how much load your battery has, the alternator will still function.

However, if your electrical uses a load like radio, lights, fan, etc., that exceeds the amount of charge that your battery receives from your alternator, it will end up discharging your battery. 

While Parking

Usually, the alternator takes about 30 minutes to charge your car’s battery, but this will depend on your car’s system.

Usually, new versions of cars have more upgrade systems, which is why in just a few seconds, it charges the battery, and the car is ready to go. However, if you have older versions of cars, it will take more minutes to start its engine and vice versa.

Does The Old Alternator Charge The Battery Slower?

Yes, old alternators charge batteries slower. When your car’s battery gets old, it needs more charge, and if you’re planning to change your battery without doing an update to its system, it might result in overcharging.

Hence, it will still charge, but it takes more time before you can start your engine. Therefore, it is not appropriate if you are in a hurry or going to special events. 

What Can You Do To Improve The Battery Charging Time?

Below are some ways that will help you improve your battery charging time:

Use A Trickle Charger

It is a device that delivers efficient electricity to your batter from the power outlet in a slow and steady phase. 

Your car doesn’t need to be charged right away; a slow phase charger is much better for your car. The trickle charges contain an electric cord with a plug and two jumper cables with alligators clips. 

Clean Your Battery Terminals

Of course, cleaning your battery terminals makes it efficient for the electricity to pass through the cable to your battery. 

Moreover, if you’re cleaning your car’s battery terminals, don’t use your bare hands, instead use sandpaper to avoid any accidents and burning.

Remove The Battery Cell Caps

If you’re charging your battery, you need to remove its cell caps. It is usually located at the very top of the battery. 

Attach Your Charger Cables Properly

When attaching your charger cables, you need to turn off your car first. There are two wires, the red one is for the positive terminal, and the other one is for the negative; attach it properly and slowly.

By doing these, you can assure that the battery charging time of your car will improve; follow the steps correctly, and your car battery condition will improve.


In summary, your car battery degenerates over time, so maintaining and upgrading is vital to avoid any problem.

Following the steps above on improving your battery charging time will ensure that your car will work properly.

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Image credits – Canva

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My name is Hank, and I've been in the automotive industry for 27 years. I've been working in my own auto repair shop for the last 13 years, and now I want to help you here, on my blog. Let me know if you have any questions. Read more