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Why Is My Car Battery Overheating? (9 Reasons + Solutions)

October 16, 2021

Is your car battery overheating

While your battery will get warm during everyday use, it’s an entirely different story if the battery is smoking hot. 

If you suspect that your car battery is overheating, don’t panic. 

In this article, we’ll explore the nine most common causes for an overheating battery. We’ll then cover five tips to help prevent your battery from overheating before looking at some frequently asked questions

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Let’s get started.

Is It Normal For My Car Battery To Get Hot?

Yes, it’s perfectly normal for your car battery to become warm during regular use. 

Temperatures under your hood can quickly reach over 200℉. 

However, unless your battery is scorching hot, is swollen, or smells, it can be tough to differentiate between a hot battery and one that’s overheating.

In general, your battery’s optimal temperature is 77℉ (25℃). 

When temperatures dip below this level, the battery capacity lowers, and charging times increase.

On days when the temperature exceeds 77℉, the battery is more likely to self-discharge, which can cause irreversible damage to the battery by reducing its stored charge. 

Now we know that batteries are supposed to get hot, let’s look at some causes for your car battery overheating. 

9 Reasons Why Your Car Battery Is Overheating

There are lots of potential reasons why your car battery is overheating. 
Let’s take a look at some of the more common causes. 

1. Defective Alternator Or Voltage Regulator

The alternator is the part of your car responsible for recharging the battery. If your alternator has developed issues, it may be sending too much voltage to the battery, causing it to heat up and swell as a result. 

If you suspect you have a faulty alternator, book an appointment with a mechanic ASAP. 

Driving with a faulty alternator can cause severe damage to expensive electrical components in your car. A faulty alternator can also lead to a dead battery. 

The voltage regulator, on the other hand, ensures a constant flow of voltage to the battery. Without this component, the alternator may overcharge the battery. 

Eventually, overcharging can cause excess heat, which may start boiling the electrolyte solution inside the battery. 

2. A Weak Battery

Sometimes a hot battery is just a hot battery. 
Other times, however, a hot battery can be a sign that it’s failing. 

If your battery is on its way out, the alternator will need to work harder to keep the battery charged. This constant charging can cause the battery to heat up. This is exacerbated by sitting near an overheating engine. 

If this is the case, your battery light will indicate that you need to have it replaced as soon as you can. 

An overheating battery can present a dangerous situation for anyone near the car. If it continues heating up, the electrolyte solution can boil and ultimately cause the battery to explode in a shower of battery acid. 

However, before replacing a bad battery, it’s a good idea to be safe and have your entire charging system checked by a qualified mechanic. 

You could do a rudimentary test yourself by examining the battery terminals for corrosion. Corrosion buildup will show as an excess of white, blue, or green powdery substance.

And if you’re wondering whether electric car batteries can overheat, the answer is yes. But it’s far more unlikely.  

3. Short Circuit

There are two kinds of short circuits a battery can experience, an internal and external short. 

With the more traditional flooded batteries, each cell contains two lead plates (one positive and one negative) suspended in an electrolyte solution. 

An internal short circuit can occur if these two plates come into contact with each other — as when the separators melt from an overheated cell. 

Fortunately, many late-model cars come equipped with AGM batteries as standard, given their improvement over the previous generation of flooded or “wet cell” batteries.

AGM batteries are more resistant to damage from shocks and vibrations and are unlikely to experience a short. These batteries have a fiberglass mat separator between the lead plates, effectively removing the chance of an internal short. 

A shorted battery can be dangerous as it may explode if it keeps shorting. However, the battery cells will often break before an explosion happens, effectively killing the battery.

An external short occurs when the battery terminals come into contact through a piece of metal. Causing an external short is unlikely but can happen if you work on the terminals with metal tools. 

An external short will cause unnecessary heating and may result in the battery exploding. To avoid causing any potential damage to your battery and yourself, always disconnect the negative terminal before working on your battery

4. Improper Charger Use

If you need to use a battery charger, make 100% sure you have the correct charger for the type of battery. Using the incorrect charger can burn out the battery. 

It’s important to remember that a battery charger specifically made for flooded cell batteries should never be used on gel and AGM batteries. 

AGM batteries work by discharging slowly, and therefore need to be charged in the same way. 

Flooded cell batteries are a little more durable in this way. Occasionally overcharging them isn’t a big issue, and you may just need to refill the battery fluid.

Fortunately, most modern car battery chargers have options for whichever battery type you have.

Also, make sure not to overcharge it yourself. 
Your battery’s charging time depends on your charger’s amperage. At 15 amps, for example, it’ll take about two hours to fully charge, whereas the same battery could take about six hours at five amps. 

As for AGM batteries, most manufacturers recommend charging them for at least five hours. 

If in doubt, have a professional mechanic check your battery as part of your summer car maintenance routine. 

5. Loose Terminal Connections 

A loose connection on your battery terminal can cause the battery to heat up by increasing the resistance. 

Whenever you finish any work on your battery, always ensure the connections are clean and secured tightly. Both a buildup of corrosion and a loose connection increases the electrical resistance. 

6. Wrong Grade Battery Cables

Using poor quality or the wrong type of battery connecting wires can also increase the resistance and create excess heat. 

If they are of poor quality or are too small to meet your car’s power requirements, the cables themselves can overheat and melt onto the battery terminals. 

7. Extreme Temperatures In The Engine Bay

The engine bay can become extremely hot when driving, especially during the summer heat. Of course, it’s perfectly normal for this to happen — heat is a by-product of the combustion process. 

Generally speaking, your car battery should be able to withstand most types of weather, provided you use your car regularly and practice proper maintenance. 

However, extreme heat from the car engine and radiant heat from the ground coupled with hot weather can cause the battery fluid to evaporate prematurely. Engine overheating may exacerbate or even cause overcharging issues. 

While unlikely to happen if your cooling system is functioning as it should, you should always keep a close eye on your temperature gauge. 

8. Malfunctioning Cooling System

Almost all cars employ a liquid cooling system. The cooling system helps prevent an overheating car by sending coolant around the engine block, picking up heat from the engine before flowing through tubes in the radiator. 

Once in the radiator, the cooling fan or radiator fan blows air through the grill into the engine compartment, cooling the liquid.

If there’s damage to the cooling system or certain components, the engine can overheat. Parts like the thermostat and the serpentine belt, which often power things like the water pump, are vital in preventing an overheating issue. 

If that happens, the battery will begin heating up. If you suspect your car engine is overheating, stop driving immediately and call a reliable mechanic. 

9. A Large Draw On The Battery

Just as rapidly charging a battery can cause it to overheat, so can a rapid discharge. 

Too much demand on your battery, like using all your car’s accessories while trying to charge your laptop, for example, can cause your battery to heat up. It’ll attempt to convert chemical energy into electrical energy faster than it’s able to. 

5 Actionable Tips To Prevent Your Car Battery Overheating

An overheated battery can be a major inconvenience. 

Rather than go through all that hassle, try and avoid it happening in the first place by following these tips: 

1. Be Mindful Of The Weather 

If you live in a hot area, try to avoid driving long distances. 
Or, if you have a long drive ahead of you, make regular stops to let the engine cool down.

Parking in the shade during a sweltering day can go a long way in reducing the temperatures under the hood.

2. Store Your Battery 

If you’re not planning on driving your car for a while, you can prevent your battery from overheating while you’re away by removing it

Ensure you wrap the battery and store it away from any metallic objects to avoid an accidental external short.

3. Check The Battery’s Condition

Most car batteries tend to last between 3-5 years. 
Performing a quick visual inspection can tell you a lot about its condition. 

Weak, older batteries can require additional charging and often struggle with delivering the required output. This makes them more susceptible to overheating, especially if operating in an overheated engine. 

Doing a visual inspection can help you identify unpleasant smells or corrosion buildup on the terminals before it turns into an overheating issue. 

4. Check Your Coolant Level

Check your coolant reservoir to make sure your car’s coolant level is alright. Without enough coolant, your car can quickly overheat. 

Make sure to regularly check your coolant level during summer. If it needs a top-up, remove the radiator cap and pour in the coolant, making sure not to pass the max line. 

5. Use Your Heater

If you’re driving and notice your battery light or check engine light activates, or if your temperature gauge is climbing, you can use your car heater. Doing so might be enough to help prevent an overheating car engine. 

Your car’s heater is actually quite a clever piece of technology, serving two purposes. 
Aside from heating the interior of your vehicle, it also helps regulate the engine temperature. 

While most of the heat exits through your exhaust system, the coolant handles the rest of it. Once the coolant has collected heat from around the engine and flows to the radiator, it reaches the heater core, warming it up. 

This creates warm air when you turn your heater on. 
As a result, if the thermostat reads excessive heat from your engine, the heater can help regulate the temperature.

Now that we’ve had a look at how to prevent your car battery from overheating, let’s address some common questions. 

2 Car Battery Overheating FAQs

Here are answers to three common questions relating to an overheated car battery:

1. What Happens If My Car Battery Overheats?

If your battery is overheating quite severely, the first thing you might notice is a rotten egg smell. Standard lead-acid batteries contain a mixture of water and sulphuric acid. It’s the sulphuric acid that gives off a bad smell.

Once the battery reaches a certain temperature, the solution may start evaporating, which upsets the balance of the mixture. This can cause the solution to boil and overheat the battery, producing an unpleasant smell. 

2. What Should I Do If My Car Battery Overheats?

If your check engine light illuminates and you suspect the car battery of overheating, it’s best to get a certified mechanic to take a look as soon as possible. 

Unfortunately, if you have a maintenance-free battery, like a gel or AGM battery, there’s nothing you can do about the internal structure, and you’ll need a new one. 

With a flooded battery, you can remove the caps and check the electrolyte level to see if it needs a top-up of distilled water. Fill it just enough to cover any exposed plates by 1/8 of an inch. 

And, of course, never try to jump-start a car with an overheating battery. Doing so can destroy the jumper cables and damage your vehicle.

If you’d rather not deal with the hassle, you can get a professional mechanic to handle it for you, like RepairSmith

RepairSmith is a convenient mobile vehicle repair and maintenance solution, available 7-days a week with easy online booking. They’ll send ASE-certified mechanics to your driveway and quickly replace your car battery. 

For an accurate cost estimate for a battery replacement, fill out this form

Wrapping Up

Even if you’ve taken good care of it, faulty components like a radiator fan, radiator cap, or serpentine belt can result in car battery overheating. 

If your battery is suffering from excessive heat, your safest option would be to call a reliable mechanic and have them safely remove and replace the battery ASAP. 

Fortunately, you can contact RepairSmith, and they’ll have your car up and running again in no time. Contact them and let their ASE-certified mechanics do the heavy lifting for you!