3 Common Reasons Why Your ATV Battery Is Getting Hot

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An ATV battery can warm up during charging but should never get hot to the touch or overheat. This applies both when riding or charging it with an external battery charger. A battery that heats up more than usual is a sure sign of an issue that needs immediate attention. 

The most common cause of an ATV battery that is getting hot is from overcharging or due to a defective battery. Overcharging may occur if the voltage regulator on the ATV is defective or charging the battery at too high of an amp setting with an external charger.

In this post, we will closely examine all of these scenarios.

Faulty Voltage Regulator Rectifier

A faulty regulator rectifier can cause overcharging that will overheat and potentially damage the battery.

The voltage regulator rectifier plays a crucial role in the ATV’s battery charging system, serving two essential purposes.

Firstly, it converts the alternating current (AC) from the stator to the direct current (DC) that the ATV’s electrical components can utilize. 

Next, it regulates the voltage to a stable output of about 14.5V. The input voltage from the stator fluctuates with the engine’s RPMs and can reach levels as high as 20V or more. 

Since the electrical components of an ATV, including the battery, are not designed to handle voltage levels higher than about 14.5V, we must regulate the input voltage to a stable operating voltage. 

When the regulator fails, it will distribute excessive voltage that can damage components and overcharge the battery. Overheating of the battery is a sign that it’s being charged with a too-high voltage. 

You can use a multimeter to test if the regulator if it’s working correctly; follow these steps:

  • Set your multimeter to 20VDC.
  • The red lead goes to the positive battery terminal, while the black goes to the negative terminal.
  • With the engine off, you should read about 12.4 to 12.6V. This indicates a healthy battery.
  • Start the ATV and read the voltage while running at an idle, then rev up to about 3000RPM
  • The voltage should increase to about 13-14.5 volts. Some regulators max out as high as 14.8V.
  • Should the voltage fluctuate or present a reading outside this range, it signals that your regulator may be defective.

Another indication of a faulty voltage regulator is a noticeable fluctuation in the brightness of the lights when you rev up the ATV. At levels above 14,5V, the bulbs will glow much brighter than usual until they eventually burn out completely.

To further test your voltage regulator, you can use the multimeter to see if the diodes inside the regulator are working correctly. Partzilla.com has made an excellent video demonstrating this procedure:

ECU voltage regulator ATV
This is what the voltage regulator rectifier on most Polaris ATVs looks like.

Click here to learn more about how the charging system on an ATV works.

Damaged Battery Cell

A bad battery cell or other internal battery faults may cause the battery to overheat when charging.

If your regulator/rectifier checks out fine, the problem is likely with the battery.

A battery is divided into cells, each holding a specific portion of the battery’s overall voltage. When one cell fails, it will negatively affect the combined voltage of the battery.

A 12V battery is typically 2.2V x 6 cells, which equals 12.6V nominal voltage. They are designed to be charged with a charge voltage of about 14.5V. If one cell shorts, often from internal sulfation, you are left with only five working cells. 2.1V x 5 cells equal only 10,5V nominal voltage. 

The ATV’s charging system or external charger will see it as low, forcing the five working cells to accept the total charge. This will cause the battery to overcharge and heat up.

If you suspect that your battery is bad, you test it yourself by performing a so-called load test (you will find instructions on how to do it in this post), or you can take it to your dealer, and they will test it for you.

Charging Too Fast or for Too Long

Charging a battery with too high a current or an excessive duration causes overcharging.

If your battery is not getting hot from regular riding, but when charging it with an external battery charger, you are likely either:

  • Charging it using too high of charge current
  • Charging it too long using a manual charger
  • Charging it in the wrong charge mode

Ensure You Use the Correct Amp-Setting

ATV batteries are comparatively small; therefore, requiring charging using a correspondingly low charge current (measured in amps, A).

A good rule of thumb to know the proper amperage to charge your battery is to divide its Ah- rating by ten. A 15Ah battery should use a charger with no more than 1.5A power output. Most major ATV battery brands also provide charging data printed on the battery casing. 

This illustrated step-by-step guide will tell you how to charge any ATV or UTV battery.

Never charge an ATV battery with more than 3A. If you do, it will overcharge and therefore get hot. 

Never Leave a Battery Unattended With a Manual Charger

A manual charger will continue sending amps into the battery even after it is fully charged and can no longer absorb more current. This will cause the electrolyte fluid inside the battery to “boil” until it evaporates completely. 

You may notice a funny odor from the evaporated electrolyte when this happens. Some say it smells like rotten eggs. This is a sign that you are overcharging the battery.

Caution! The gasses created from overcharging a battery are highly explosive. If you overcharge a battery, unplug the charger but leave it connected to the battery to avoid sparks. Allow the battery to vent for at least 30 minutes before removing the positive and negative charge leads. 

On the other hand, automatic chargers know when the battery is getting near a full charge. They will gradually decrease the amperage until it stops completely when the battery is full. 

After the battery is fully charged, the charger automatically switches over to maintenance mode. In this state, the charger will only add a small charge when necessary to keep the battery topped off. This is great when the ATV sits for an extended period without being ridden. 

Also, note that a typical automotive trickle charger can be too much to handle for an ATV battery. 

Using the Wrong Charge Mode Can Also Cause Overcharging

Different types of batteries (lead-acid, AGM, GEL, and so on) require slightly different charging currents. GEL batteries, for example, use a higher current than you would use on a typical flooded lead-acid battery. 

So if you charge a conventional battery using the GEL mode on your charger, it will charge it at a higher voltage than the wet lead-acid battery is designed to handle. This may cause it to overcharge and heat up.

Other Causes of an ATV Battery Getting Hot

Lead-Acid Battery Running Low on Electrolyte

A lead-acid battery must have a minimum electrolyte level, or it may get too hot when charging.

On conventional wet lead-acid batteries, you must ensure the electrolyte level is not below the minimum mark. The electrolyte plates inside the battery should not be exposed.

Some ATVs tend to be harder on the battery than others. 

If you search the forums, you will learn that Honda ATVs are notorious for boiling batteries, leaving them low on electrolytes. Some find it takes only 2-3 years to dry their battery. 

As a precaution, I recommend having a bottle of distilled water at hand and regularly inspecting the electrolyte level. Top off any cells that are getting low.

Short Circuits

A short circuit occurs when an electric current travels along an unintended path, usually where resistance is low or non-existent. When this happens, the electrical resistance drops to very low values, causing a rapid increase in the amount of current flowing.

When a battery experiences a short circuit, the excessive current flow can produce more heat than the battery can handle. This is due to the rapid conversion of chemical energy into electrical energy and then into thermal energy because of the increased resistance in the short circuit path.

Essentially, the excess energy that can’t be effectively used as electricity (due to the lowered resistance) has to go somewhere, and it’s converted to heat.

This excessive heat can cause the battery to become very hot, and in some extreme cases, it can cause the battery to fail or even explode.

Is a Hot ATV Battery Dangerous?

Do not ignore signs of a battery that is getting too hot. Running the battery hot will likely cause permanent damage to the battery or other ATV components.

The gasses created from overcharging a battery are highly explosive. A tiny spark can lead to a potentially fatal explosion. So if your battery is getting hot, keep this in mind and be careful not to create any sparks.


Is it normal for an ATV battery to get hot while charging?

It’s normal for batteries to warm up during charging, but excessive heat may indicate an overcharging issue.

What should I do if my ATV battery gets hot?

If your ATV battery gets hot, stop using or charging it and seek professional help.

How can I prevent my ATV battery from getting hot?

Ensure your ATV is charging correctly, avoid overcharging, and keep your battery clean and well-maintained. Regular checks can prevent overheating.

Wrapping Up

Caring for your ATV’s battery and charging system is crucial for safety and longevity. Overcharging or faulty components can lead to excessive heat, risking battery and component damage. Maintain regular checks, and address issues immediately to avoid unwanted repercussions. Ride safe!

Haavard Krislok
Haavard Krislok
Haavard Krislok is an ATV and off-road enthusiast with a rich background spanning two decades in owning, maintaining, repairing, and utilizing ATVs for farming, logging, and hunting. Outside his professional life as an engineer and project manager, he cherishes recreational trail riding and is the creative force behind BoostATV.com, serving as its owner, editor, and content creator.

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