Overheating Car Battery: Common Causes and Solutions

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An overheating car battery is difficult to detect because batteries generally get hot when they are in operation. You might not even notice the battery becoming too hot until it’s too late and the damage is done.

Overheating Car Battery

This article will discuss a few symptoms of car battery overheating and what causes the phenomenon. Then we’ll discover viable methods that can help solve the problem.

What Are the Major Causes of an Overheating Car Battery?

The major causes of an overheating car battery while driving are a broken alternator, a weak battery, using improper chargers, short-circuiting, and loose terminal connections. When these things happen, you may perceive a smell of rotten eggs, the battery might die, or it might even blow up.

– A Defective Alternator and Faulty Voltage Regulator

The alternator is the main device that replenishes the power the battery discharges by converting chemical energy to electrical energy. It sends this power to the battery in just the right quantity to charge it and keep it going. If the alternator develops a fault, it may send more power than the battery requires. This excess power may end up overheating the battery and illuminating the low battery light on the dashboard.

A voltage regulator/rectifier ensures that it controls the amount of electricity sent to various parts of the vehicle. It works in tandem with the alternator to send the right amount of energy to the battery for optimal performance. If the voltage rectifier ceases to operate, the alternator may send too much power to the battery, which will result in overheating. The excess heat from the battery may boil the electrolyte, which would break it down and lead to a short battery life.

– A Weak and Worn-out Automobile Battery

A battery, like many car components, gets weak over time and needs replacement. When a battery becomes weak, the alternator will need to work harder to produce enough power to charge it.

The alternator may end up oversupplying the battery with power, leading to overheating and the destruction of the battery’s chemical components. Usually, a weak battery is indicated on the dashboard by a red light illuminating a battery sign.

– Using Incorrect Battery Chargers to Wrong Battery Types

Making use of incorrect and unapproved car battery chargers can cause overheating. For example, a battery charger designed for AGM batteries must never be used on flooded cell batteries.

Causes of Overheating Car Battery

This is because AGM batteries discharge slowly, therefore, their charges are made to charge them slowly as well. Charging flooded cell batteries occasionally won’t hurt them and sometimes all you have to do is to refill the battery fluid.

– Short-Circuiting the Battery of the Vehicle

For the novices, a short circuit is when the positive terminal of a battery connects to the negative terminal of the same battery. This can cause high currents within the same battery, resulting in overheating. There are two types of short circuits when it comes to car batteries — internal and external — and both depend on the type of battery.

Short Circuiting Car Battery

Internal short circuit mostly happens in traditional flooded batteries where the positive and negative floating plates touch each other. This usually occurs when the component that separates these plates melts due to overheating.

On the other hand, an external short circuit happens in AGM batteries where a metal accidentally connects the positive terminal to the negative terminal. This metal can be any metallic tool used to work on batteries, thus you have to be extra careful. A frequently shorted battery can result in overheating and subsequent explosion in the engine bay, leading to a dead battery.

– Loose Terminal Connections and Low-Quality Battery Cables

When a terminal connection comes loose in a battery, it builds up excessive electrical resistance, which can cause overheating. This can affect both the electrical systems in the car and the battery as well.

Also, purchasing the wrong type of cables for your car or using low-quality ones can also increase the resistance of the battery. As you already know, this excessive resistance may cause overheating and eventually damage the battery.

How To Solve the Common Causes of Overheating Car Battery?

To solve the common causes of an overheating car battery, you can try repairing the faulty alternator and voltage rectifier, repairing the weak battery, using the correct battery chargers, fixing loose battery connections, and replacing low-quality cables. You can go to a professional for these services.

Regarding what to do with a hot battery, take it out of the vehicle and place it in an airy place. However, only do this when the battery is overheating. The chemical reactions and hot weather naturally make a car battery hot, so don’t remove it just because it’s hot.

Now that we’ve discovered why batteries overheat, we’ll look at how to fix overheating car battery. We’ll also consider a few ways that you can prevent these factors from affecting your batteries.

– Repairing a Faulty Alternator and Voltage Rectifier

Repairing an alternator depends on the type of vehicle you’re driving, so you need to buy the right kit for your device. Then disconnect the positive terminal of your battery as a precautionary measure before removing the alternator. You need to notice the position and the wire harness around the alternator and then consult your car manual as to how to remove it.

Solutions for Overheated Car Battery

Now that you’ve removed the alternator, detach its rear cover, which is the plastic cover held in place by two bolts. Then remove the old voltage rectifier along with the brushes but not without taking note of all the wires and how they connect to the regulator. This would come in handy when you’re installing the new voltage rectifier. Ensure you take out the old alternator brushes and compare their length to that of the new one to see the extent of damage on the old one. Now, fix the new regulator following the instructions written in the leaflet that came with the device or on the product’s cover.

Remember to install the new brushes, fix the wires and tighten the bolts to secure the regulator. The next step is to refit the plastic cover over the rear of the new alternator and then fix the alternator, making sure that its belt is tight. Now, conduct some tests to ensure that the alternator and regulator are doing a great job. Due to the complex nature of this job, we’ll recommend that you drive to a car repair shop.

– Repairing a Weak Battery and Using the Correct Battery Chargers

To fix a weak battery that couldn’t hold a charge, just top it up with distilled water. Note that this can only work on batteries that have become weak as a result of the evaporation of their chemicals. If the acid in the battery has dwindled, then you need to add the right quantity of sulphuric acid. After refilling, recharge the battery and test whether the battery has regained its ability to hold a charge or not.

Some batteries also become weak due to old age and no amount of recharging can bring them back to life. A battery should last between three and four years, after which it would begin to lose its abilities. When this happens, the only option you have is to purchase a new battery to replace the old one. However, if the car is overheating after replacing the battery, then contact your mechanic.

Also, ensure you use the right charger for your battery to avoid damaging it. Fortunately, newer cars have different charger options for the type of battery you use, thus it shouldn’t pose much of a problem. While you are at it, avoid overcharging the battery as extreme temperatures could also cause overheating and ruin it. For example, if your battery is 15A, it may take about 2 hours to charge, but AGM batteries require about five hours to complete the charging process.

– Fixing Loose Battery Connections and Replacing Low-Quality Cables

If your battery connections are loose, the only way to fix them is to tighten them. Ensure you scan the whole charging system for loose wires and fix them. The battery terminals are the major culprits in this area, therefore make sure you screw the cables around them tight. However, remember that substandard cables can cause the cables to overheat, so make sure to purchase high-quality ones.

– Avoiding Short-Circuiting the Battery

To avoid short-circuiting a battery, always disconnect the negative terminal before conducting any work on it. Another method is to cover the terminals with non-conductive materials like tape, plastic or wood. Also, when transporting more than one battery, ensure you pack each one in a non-conductive material.

Frequently Asked Question

– Why Does the Car Overheat After Replacing Battery?

The car overheating after replacing battery problem could be a sign of a different issue that is unrelated to the new battery. The cooling system might be leaking, the water pump might be broken, or the radiator is faulty. Allow a mechanic to determine the real cause of overheating.

Overheating Car Battery Solved


So far, we’ve looked at the common causes of overheating car batteries and the practical ways to fix them.

Here is a recap of all that we’ve read in this article:

  • A faulty alternator and a defective voltage regulator can send too much power to the battery, causing it to overheat and subsequently damaging it.
  • A weak battery can also cause overheating and will need replacement just as in the case of the faulty alternator and defective regulator.
  • When you detect the loose connections are the reason for the overheating, all you have to do is to tighten them and the problem will cease.
  • However, if you purchased substandard cables and wires causing the battery to overheat, remove them and install new standard cables for your battery.
  • To avoid short-circuiting your battery, cover the terminals with non-conductive materials like wood, paper and plastic when working on the battery.

Finally, remember to use the prescribed chargers for your battery to avoid overheating and damaging them. Also, a rotten egg smell is one of the major overheating car battery symptoms which you should take seriously when you perceive it.

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