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Can You Overcharge A Car Battery?

Can You Overcharge A Car Battery?

A well-functioning battery is one of the most critical components of a car. After all, the vehicle won’t even start without a good one! To help improve your battery’s performance and longevity, you may find yourself wondering if it’s possible to overcharge a battery.

Traditional lead-acid car batteries are susceptible to overcharging when left charging continuously for extended periods. Overcharging can result in damage to the battery’s lead plates and even destroy the battery. However, modern lithium-ion batteries have internal circuits that prevent them from overcharging.

With that in mind, let’s take a look at some of the common signs and symptoms of battery overcharging.

Causes of Battery Overcharging

1. Faulty Battery Chargers 

A defective battery charger can be responsible for battery overcharging. If the battery charger has incorrect wiring, it could cause the battery to overcharge even under careful monitoring. 

2. Human Error 

Among the leading causes of battery overcharging is human error. Some car owners can opt to charge a battery without a clue of doing it correctly. For example, an incorrect amperage or voltage setting can lead to overcharging. 

3. Extreme Heat

Extreme summer heat can damage the battery if left in the sunlight over a prolonged period. High heat high will bring more battery complications leading to damage. Ensure that the battery gets the correct amount of ventilation and shade when not in use. 

4. Broken Voltage Regulators

The voltage regulator determines the amount of electricity that flows into a car battery. More so, it ensures that the battery receives a steady rate with the correct amount of energy. 

When this voltage regulator breaks, it implies that the electricity flow remains unchecked, leading to cells damage. 

Symptoms of Overcharging a Battery 

  • Hot to touch: If the battery is charging well, it should be cool to the touch. One sign that it is overcharging is when the sides are warm to the touch. We can make a routine check for such a symptom every thirty minutes when driving. 
  • Swelling: The battery sides will appear curved as long overcharging is happening over a prolonged period. Such a situation becomes real when the overproduction of gases within the battery causes bulging and swelling. Here, we must fix the problem immediately. 
  • Dropping electrolyte level: When the fluid level is frequently dropping, there might be the need to top it up to the right level. Overcharging can generate too much heat causing the electrolyte to evaporate, leading to a fluid drop. 
  • Acid scent: When we smell the acid scent as it is boiling off, then that is a sure indicator that the battery is overcharging. It is however, noteworthy that such cases are rare. 
  • High Voltage Reading: One should measure the amount of voltage to know if it ranges from 12.6V to 14.V. If the reading lies in that range, there is possibly a defective alternator that’s causing the car battery to overcharge. 
  • Battery leaks: By overcharging the battery, hydrogen gases build up, causing pressure within its housing. The pressure forces the electrolyte to leak out via housing openings. The battery fluid leaks through filler caps or vents of the battery. 

Checking Car Battery Overcharging 

1. Use a Multi-meter

When the vehicle is running, we can use it to check the amount of battery voltage. A fully charged battery reads at 12.6V. The idle one will indicate 2.1V for every six internal cells.

When I start a car without putting on the air conditioner and the lights, the voltage may increase to 14 V. We can consider overcharging if the multimeter reads more than 14.8V. 

2. Locate a Broken Alternator

The car owner should check the condition of the alternator. When the car is in operation, the alternator assists the battery to get the right amount of energy. It generates electricity and allows it to flow within the battery. 

If the alternator breaks, the battery plates shed the protective layer as a result of heat. Such an anomaly may compromise the entire structure of a car battery. 

3. Manage the Temperature 

Extremely hot temperatures can affect the condition of a car battery. The right way to avoid heat is by parking the car under a shed during hot weather. The best practice is to protect the vehicle during the hottest season of the year. 

Reconditioning an Overcharged Car Battery 

Reconditioning refers to injecting new life and improving the charging capacity of the old cells. This practice is necessary because it is cost-effective. Therefore, we save a considerable amount when compared to acquiring a new battery. 

What’s more, by reconditioning the battery, we will be regulating wastes and pollution. For instance, lead content can pose health risks to groundwater and soil. As such, the benefits are manifold. 

How to Recondition Car Batteries at Home

Is battery reconditioning a DIY job? Indeed yes, we can follow the following steps to facilitate the process in the comfort of our homes.


We will need different materials as listed below:

  • Bucket and Distilled water
  • Battery terminal cleaner 
  • Voltmeter
  • Apron 
  • Mask
  • Funnel and baking soda
  • Disposable rubber gloves and toothbrush
  • Battery charger
  • Flathead screwdriver and charger


  1. Before we begin to recondition a battery, we should always wear safety attires. As a precaution, we should use a water solution and weak baking soda as neutralizing agents for unintended splashes and spillage.
  1. Again, ensure that battery terminals are corrosion-free. We can prepare a solution of baking soda and water to the ratio of 2:1. Using the toothbrush, dip it in the same solution and rub it against the battery terminals to eliminate corrosion traces.
  1. After that, take the volt reading thanks to the voltmeter. A proper terminal connection is critical at this point. The black cable should connect to the negative terminal while the red one to the positive terminal. 
  1. The battery will be in a suitable condition if the voltage reading exceeds 12.6V. We will have to recondition it suppose the readings range from 10V to 12.6V. 
  1. Remove the battery cap using a flathead screwdriver. Secure the battery cap in a container to prevent misplacement. Gently lift the battery and empty the electrolyte in the bucket. 
  1. Never dispose of the oil battery acid solution before neutralizing it with 500g of baking soda powder. 
  1. Make a baking soda and water solution in the ratio of 2:1. Meanwhile, we can open the caps and empty the solution in the previous bucket. 
  1. Using Epson salt solution, replace the old electrolyte. 
  1. Using 12V/2amps slow charging mode, recharge the reconditioned battery for at least 24 to 36 hours. After that, we check the voltage using the voltmeter. The battery will be in perfect condition if the readings range from 12.42V to 12.6V. 
  1. Last but not least, we should now perform a load test. 

Frequently Asked Questions 

How can I fix an overcharged battery? 

Check the condition of the voltage regulator and replace it if it’s faulty. If the charger is defective, replace it with a new one. We should ensure we do not charge the battery beyond 15 V. 

Can I leave the battery on the charge throughout the night? 

The battery should not be left to charge for more than 24 hours. However, we can attain a full charge through overnight charging. 


We have seen we can overcharge a car battery. The condition of a car battery determines how the car operates. Ensure that voltage remains within the acceptable ranges. In case there are faults in the system, replace the affected components. 

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Zach Reed

Hi, I'm the founder of! Having owned a wide variety of vehicles in my life, I was astounded at how hard it can be to find answers to common automotive questions. Rather than sit idly, I decided to create this website to help others!