Informational Guide

Can You Overcharge A Car Battery?

Can you overcharge a car battery? Yes, you can, so use this guide to show you the correct way to prevent damage.

Your automotive battery ensures that your vehicle starts every morning before work. When the battery starts to die, you want to charge it, but can you overcharge a car battery?

Yes, you can, so you need to be careful. In this guide, we discuss car battery overcharging and show you the correct way to charge a car battery.

When you overcharge your car battery, it dies. However, if you are running an older battery, it can be dangerous to overcharge it.

As the sulfuric acid and water inside the battery case begin to boil, the battery itself can start to swell. Eventually, the plastic casing is going to melt. Additionally, the flammable hydrogen gas can build up. If there is a tiny electrical spark, the battery could explode.

Obviously, this is all the worst of what could happen. However, you don't want to find out what happens if you leave a car battery charger on too long.

Can You Overcharge A Car Battery

Most Common Causes Of A Car Battery Overcharging

Can you overcharge a car battery with a charger? Yes, so you want to know some of the causes of battery overcharging before they occur.

  • Broken voltage regulators 
    The voltage regulator ensures the right amount of power is flowing to the battery. If it is broken, too much or too little voltage can seep through, causing trouble with the charge.
  • Broken alternator 
    The alternator needs to give the battery energy to recharge while the vehicle is on. When it breaks, it can cause too much voltage, which leads to battery overcharging. Other times, when the alternator fails, it stops charging the battery altogether.
  • Improper car battery charger use 
    If you don't know how to charge a car battery, you could do something wrong that causes it to overcharge. It's important to know how to use a car battery charger before connecting it.
  • Faulty or broken car battery chargers 
    Even if you are skilled at charging a car battery overnight, the charger itself could be faulty. If it is allowing too much voltage through, it can cause damage to the battery.
  • Extreme heat 
    It's essential to have the best car battery for hot weather. Even when you do, the extreme heat can still take a toll on the battery and cause voltage issues. Try to keep your vehicle in the shade when the temperatures are hot.
  • Trickle chargers left unattended 
    You must know how long to let a car battery charge to protect it from damage. How long do you charge a car battery? It depends on the type you are using, so be sure to read the owner's manual.
How Many Amps To Charge A Car Battery

Symptoms Of An Overcharged Car Battery: How To Check For Signs

If you aren't sure how long to charge a dead car battery, you could easily overcharge it. Some of the most common symptoms that you have overcharged your car battery include a loss of water, complete battery failure, or a hydrogen explosion. On newer cars, you might also get a dashboard indicator telling you something is wrong with the battery.

With the best car battery tester, you can see the health of your automotive battery and watch for signs of overcharging. You should know how to read a car battery charger and how to read the tester. A fully charged battery is going to read 12.6 volts when it's not in use. Once you start running the vehicle, you should see around 14 volts. If it is higher than 14.8 volts, the alternator might be overcharging the battery.

Correct Way To Charge A Car Battery

How To Charge A Car Battery Correctly: Step By Step Guide

It doesn't take a lot of skill to learn how to charge a car battery at home and figure out how long should you charge a car battery. In this section, we will discuss how long to trickle charge a car battery and the steps you should take.

While you will achieve the best charge with the battery unplugged, you can move forward with charging a car battery while still connected.

  • Gather your trickle charger and connect it to the appropriate terminals.
  • Check the setting to ensure you are on the lowest option. It's important you know how many amps are in the car battery and how many amps to charge a car battery.
  • Only charge the battery for the required amount. Do not leave it connected for longer than needed.

If you prefer, it's also possible to learn how to charge a car battery with a best car battery for hot weather and how to charge a battery without a charger.

People Also Ask (FAQs)

Can you leave a car battery charger on overnight? Is it bad for the battery to charge overnight?

It depends on what charges a car battery. If your trickle charger has a float mode, it will automatically slow the charge down once it is full. Otherwise, if the charger needs supervision, you shouldn't leave it connected overnight.

Does a new car battery need to be charged?

Usually, the new car battery is completely charged, but it never hurts to drive a little, to be sure. Do you know how long to leave a car running to charge battery? Typically, a short 15-minute drive on the highway should be enough to charge the car battery.

How much charge does a car battery need to start?

The battery must be at least 75% in order to start. Can you fully charge a car battery with jumper cables? No. While the jumper cables might help you get started, the battery will not be at full capacity. You must ensure it gets charged before you shut down the engine or connect a trickle charger to it when you get home.

What if my car battery won't hold a charge?

If the car battery appears completely dead, it might help to try battery reconditioning. However, if that doesn't work, you will need to replace it.


Now that we have answered how to know when a car battery is fully charged, it's time for you to ensure this vital piece of equipment is in its best shape. Hook up your car charger and make sure you don't overcharge your precious battery.