Can You Overcharge A Car Battery?

1 5 Signs Of An Overcharged Car Battery

When the battery is overcharged, it starts to show certain signs of failure. Being aware of these signs can help you avoid ruinous results. 

Reduced Electrolyte Levels

This can be found in older flooded cell lead-acid batteries with vent caps. You may notice that the battery has lower levels of electrolyte solution in need of topping up more often than usual. This can indicate an issue with your charging cycle. 

Hot Battery

As explained before, overcharging causes the electrolyte to boil. This means the battery becomes excessively hot, making it too hot to be able to touch. Note that the normal charging process also increases the battery temperature, however, it is not very severe. 

Release Of Gasses

If the battery is overcharging or charging at a very fast pace due to high amperage, the battery will release hydrogen and other gasses through the vents. This means the electrolyte is evaporating rapidly and is evident as the gas escapes the battery. 

Swelling And Cracks

In a sealed battery, there is no way for the built-up gasses to escape which causes the battery to swell up with the increase in internal pressure. You may notice the sides of the battery bulging out or in some cases fissures running across the plastic body. You can notice other signs of battery deformation all indicating overheating due to overcharging. 

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2 What Causes Car Battery Overcharging?

In normal conditions, the battery in a vehicle is charged by the alternator continuously as the vehicle is driven. The alternator spins with the engine and creates electricity which is stored in the battery. This helps keep the battery charged and ready for use when starting the vehicle. However, many factors influence the charging ability of the battery and so, apart from alternator failure, battery overcharging can be caused due to other reasons as well. Here are the reasons for battery overcharging:

Bad Alternator Voltage Regulator

A voltage regulator is a device that controls how much voltage is supplied to the battery as the alternator spins. The alternator voltage fluctuates with the engine rpm, however, the voltage regulator ensures the battery gets a constant voltage which is close to 14 – 14.5 volts. This charges the battery continuously. So if the voltage regulator fails, the battery will receive higher voltages thereby overcharging the battery.

Faulty Alternator

In most cases if the alternator fails, it produces very little or no voltage which will cause the battery to discharge rapidly and die. However, it is possible for the alternator to overcharge the battery when it fails. This is mainly caused when using an incompatible alternator or if the battery current sensor fails. This sensor is mainly used to determine the actual battery voltage. If it fails the battery will be supplied with excess voltage to compensate resulting in overcharging. 

Improper Battery Charger Usage

If the vehicle is not driven for a long time, the battery will slowly lose its state of charge. This does not necessarily mean the battery is dead, but just that it does not have enough charge to power the engine. In such cases, you need to use a battery charger to charge the battery and restore its state of charge. A similar thing is done at the stores where batteries are sold. Since the batteries sit on shelves unused, they slowly begin to die. This necessitates the use of a battery charger to manually charge the battery to the correct voltage. 

But the problem of overcharging or even undercharging often arrives from the use of battery chargers. Since a lot of users are unfamiliar with how to use a car battery charger, resulting in a poorly charged battery. The most common practice when using battery chargers is leaving the battery on the charger overnight. This can be extremely detrimental to the life of the battery as the battery is overcharged for a prolonged period, causing irreparable damage. 

Apart from prolonged charging spans, using the wrong charger settings like the amps, voltage, improper connections, or even an incompatible charger can cause overcharging and heating of the battery leading to a dead battery or much worse: an explosion. It is important to follow the guidelines mentioned for the charger and also the battery. This can help you determine the proper settings, connections, and charging times for a secure and effective charging process. 

Bad Battery Charger

Cheap and knockoff battery chargers are commonplace these days which is a probable cause for battery damage. If you have an old battery charger, there is a chance it has failed which is causing issues while charging the battery. A bad battery charger can charge the battery at a very fast pace or at very high voltages or amperage which will not only overcharge the battery but can also cause irreparable damage to it. Some chargers are designed for use only on specific types of batteries, and using an incompatible charger can also damage the battery.

3 What Happens If You Overcharge A Car Battery?

The effects of overcharging depend on the severity of the overcharging process like how often it occurs and for how long. If the battery is overcharged regularly it loses its overall ability to hold a charge and eventually dies. Whereas if it is overcharged for a very long time, the electrolyte solution within it starts to boil producing hydrogen which can lead to an explosion. Here are all issues that can occur:

Reduced Battery Lifespan

Dead Battery

As the battery overcharges repeatedly, it eventually loses enough electrolyte solution that it can no longer hold a charge which is when the battery dies. This is actually the best-case scenario as it prevents any disastrous consequences. 

Damaged Battery Or Explosion

When the battery is overcharged, the internal temperature increases which leads to electrolyte evaporation and gassing. Gassing is the release of hydrogen gas within the battery. In older flooded cell batteries, there are vent caps on each cell which are used for topping up the electrolyte with distilled water. This meant that if the internal pressure increased, these vent caps would allow the release of gasses without catastrophic results. However, if these vent caps are sealed, the battery can swell up in size due to the increased pressure and either crack and release the gasses along with the solution or cause an explosion. 

In modern sealed lead-acid batteries, there are no vent caps for each cell, instead, there is a single vent to relieve any pressure buildup. If this vent is blocked due to dirt or contaminants, the battery is susceptible to swelling and cracking or in the worst case: explosion. 

4 FAQs

Can You Overcharge a Car Battery?

Yes, overcharging a car battery can damage it completely and affect its service life. Overcharging can cause excessive gassing that ruins the device, and it can also accumulate flammable hydrogen. Common causes of an overcharged car battery include a bad alternator, a faulty voltage regulator, and human error. It is important to note that overcharging a battery can cause the pressure to build up extremely high, which can lead to an explosion if the oxygen and hydrogen combine to make an explosive mixture. Therefore, it is recommended to avoid overcharging your car battery.

How to Fix an Overcharged Battery?

If you have overcharged your car battery, it is important to take immediate action to prevent any further damage. Here are some steps you can take to fix an overcharged battery:

1. Disconnect the battery: Disconnect the battery from the device it is powering.
2. Remove the electrolyte: Remove the battery’s electrolyte using a syringe or other tool.
3. Mix a solution: Mix a solution of Epsom salt and distilled water.
4. Fill the battery: Fill the battery with the solution.
5. Recharge the battery: Recharge the battery at a low charging voltage using a battery charger.

It is important to note that overcharging a battery can cause the pressure to build up extremely high, which can lead to an explosion if the oxygen and hydrogen combine to make an explosive mixture. Therefore, it is recommended to avoid overcharging your car battery.

What are the Symptoms of an Overcharging Alternator?

When an alternator overcharges, it can cause a variety of symptoms. Here are some common symptoms to look out for:

• Flickering dashboard lights or headlights
• Brighter lights than usual
• Dashboard warning lights
• Blown fuses and bulbs
• Damage to the car battery
• A red battery light on the dashboard
• Low battery electrolyte
• Battery heating
• Swollen battery
• Seeping battery

What Causes a Car Battery to Swell?

A car battery can swell due to several reasons, including overcharging, high temperatures, and age. Overcharging occurs when the battery is continuously charged at a higher voltage than recommended, leading to the production of excess gas and subsequent swelling. High temperatures can also cause the battery to swell as the heat accelerates the chemical reactions inside. Additionally, as batteries age, their internal components deteriorate, leading to the release of gas and swelling.

Can you Overcharge a Car Battery with a Trickle Charger?

A trickle charger is a device that supplies a low current to a battery over an extended period of time. It is designed to maintain the battery’s charge level and prevent it from discharging completely. Unlike a regular charger, a trickle charger does not supply a high current that can damage the battery. Therefore, it is unlikely that a trickle charger will overcharge a car battery. However, it is important to note that leaving a trickle charger connected to a battery for an extended period of time can cause the battery to dry out and lose its electrolyte. This can lead to permanent damage to the battery. Therefore, it is recommended to use a trickle charger only when necessary and disconnect it once the battery is fully charged.

What Stops the Alternator from Overcharging the Battery?

The voltage regulator is responsible for preventing the alternator from overcharging the battery. The voltage regulator controls the amount of current that flows from the alternator to the battery, ensuring that the alternator’s output voltage does not exceed the safe limit for charging. If the alternator produces too much voltage, the voltage regulator will cut off power to prevent damage. Other common causes of an overcharged car battery include a bad alternator, a faulty voltage regulator, and human error.