ATV batteries have a limited lifespan and will eventually need to be replaced. To determine if your battery is failing or just needs a recharge, watch for these common signs indicating a battery is going bad.

1. Slow Engine Cranking

The battery’s primary purpose is to power the electrical starter that, in turn, starts the engine.

When the battery becomes weaker, you notice that the engine cranks slower until there isn’t enough power to start the engine.

While slow engine cranking can be an early sign of a battery going bad, it can also just be that the battery’s state of charge is too low, and it needs a proper charge with an external charger.

ATV batteries are prone to draining faster than the ATV charging system can keep up. Battery draining can happen due to overusing power-hungry accessories such as an electric winch or when an electrical issue causes a parasitic amperage draw that drains the battery overnight.

Remember that it’s normal for the engine to crank more slowly in cold weather. This happens because the engine oil thickens in the cold, making the engine harder to turn. Also, cold temperatures can reduce the capacity of even healthy batteries.

2. The Battery Warning Light Turns On

The battery warning light on the instrument panel could signal an early indication of a failing battery in your ATV.

However, most modern ATVs don’t have a designated battery warning light. Instead, they have a check engine light. When this light illuminates, it’s accompanied by a diagnostic code that helps identify the problem, which may involve the battery.

If you see a check engine light accompanied by a “system power” diagnostic code, the system voltage is either too high or too low. Various issues can trigger this warning:

A faulty stator.
A faulty voltage regulator.
Loose, damaged, or corroded wiring.
A battery that is too drained and needs a charge.
A battery that is damaged and needs to be replaced.

The easiest way to troubleshoot a battery warning light is to charge it with an external charger to see if it charges and test if it holds a charge.

3. The Battery Won’t Charge

Often, you’ll find that a proper charge with an external charger will bring the battery back to working order. But if the battery has gone bad, it may no longer be capable of taking a full charge.

A modern automatic charger usually refuses to charge a bad battery. When a battery becomes heavily sulfated or if a cell is dead, the charger notices in the initial stages of the charging process and won’t attempt to charge the battery.

If you use a conventional manual charger, the battery may seem to charge as usual, but when you test the voltage afterward, you find it did not charge as it should.

Use a multimeter in the 20V DC setting or a volt-meter to read the battery voltage. The red lead connects to the volt (V) port and onto the positive battery terminal. The black lead connects to the COM port and goes to the negative battery terminal.

When charged overnight, a healthy battery should reach a state of charge of at least 12.4V. If it doesn’t, the battery is too sulfated and needs to be replaced.
If you cannot charge the battery above 10.5V, it has a dead cell.
If the battery reads 0V, it has an internal short circuit.

Some modern chargers have a “Recondition” mode that is designed to remove some of the sulfation. This feature can be helpful to restore a battery in the beginning stages of sulfation.

Note that some smart chargers refuse to charge an otherwise healthy battery that’s been drained overnight. A completely drained battery does not necessarily go bad if you charge it immediately.

Here is a cool trick to try when your smart charger refuses to charge a drained battery.

Check out this guide to troubleshoot a scenario when a battery won’t charge.

4. The Battery Won’t Hold a Charge

Often, you find that a battery you suspect has gone bad seems to accept a charge but loses it after just a day or two. A bad battery can lose its charge even when disconnected from the ATV.

When a battery has finished charging, it holds a higher but temporary surface charge that goes away after a few hours. When you read the voltage, it may indicate a healthy level above 12.4V. But after a day or two just sitting on the bench, a rapid self-discharge rate may have caused the voltage to drop well below your previous reading.

Battery not holding a charge can happen when fluid levels are low on a serviceable battery (conventional lead-acid battery with removable caps).

When a sealed battery no longer holds a charge, it has likely gone beyond repair and needs replacement.

5. Bulging Battery Casing

Overcharging is when a battery is charged at too high of a voltage and can cause permanent damage to the battery. Typical signs of overcharging are when the batter loses its capacity and the outer casing looks bloated with bulging sidewalls.

Swollen or bulging battery sidewalls are a definite indicator that the battery needs to be replaced.

Remember, it’s crucial to investigate and address the cause of this overcharging condition to prevent future battery damage.

Using the wrong charger or charge mode for the battery type can cause an overcharge, but so can a defective voltage regulator.

6. Cracked Battery Casing

The battery’s outer casing is made from a rugged, impact-resistant plastic material that can handle most of the abuse rough ATV riding can throw at it.

But from time to time, the outer casing may crack, spilling out the internal fluid, which has an immediate negative effect on battery performance.

Inspect the battery to look for physical damage. You may need to disconnect and remove the battery for a good view.

If there are any signs of leaked battery fluids or cracks in the battery casing, you must replace the battery before using the ATV. If the leak is small, you may not find liquid battery acid, but look for white residue in the battery tray from dried battery fluid.

7. Misshaped or Melted Battery Casing

If exposed to too high temperatures, a battery casing can melt and become misshaped. That is why it needs to be installed at a safe distance from the exhaust system.

If the casing has defects near the battery terminal, it can be caused by a short and should qualify for a battery replacement.

8. Lose or Damaged Battery Terminals

The battery terminals should not show movement when you (gently) wiggle the wires.

While not very common, battery terminals may come loose from hard impacts or fatigue when a battery loose battery moves around in the battery compartment or tray.

Loose or damaged battery terminals are dangerous and can cause a short circuit, which can cause the battery to explode.

9. Discolored Battery Fluid

On a conventional serviceable lead-acid battery with removable battery caps, you can inspect the condition of the battery fluid.

Caution: Always wear eye protection when working on a battery.

If the fluid levels are low, you should top off with distilled water so the level is between the maximum and minimum mark before charging.

The battery acid should be clear and colorless. A dark or brownish fluid in one or more cells indicates a bad battery and renders the battery useless.

Why Do ATV Batteries Go Bad?

While some ATV batteries go bad from overcharging, physical damage, high temperatures, or short circuits, the number one cause is an internal chemical process known as sulfation.

When an ATV battery discharges, a chemical reaction occurs, producing a by-product called sulfate, which are salts of sulfuric acid. This accumulation of sulfate salts on the battery’s lead plates is known as battery sulfation.

Recharging the battery helps reverse this process by converting most sulfate salts/crystals back into electrolytes (battery acid).

Despite this, not all sulfate salts are removed during charging. Some remain on the lead plates. Over time, as the battery ages, these residual sulfate salt crystals build up, leading to reduced battery efficiency.

The battery gradually loses some of its capacity (its potential to reach a full charge) as the sulfate crystals increase in size and harden on the lead plates. The sulfation also increases the battery rate of self-discharge.

Sulfation can be kept at a minimum by ensuring the battery stays at full charge most of the time.

The sulfation process accelerates when a battery sits at a drained or low state of charge for extended periods, such as through winter storage.

That is why your best hedge against a bad battery is to leave it on a maintenance charge throughout winter storage and to top it off now and then through the riding season.

When a battery has become sulfated to a point where it can no longer hold a charge, your only option is to get a replacement battery.

How to Test if Your ATV Battery Is Bad

If you’re uncertain whether your ATV battery is completely worn out or still usable, there are steps you can take to assess its condition.

You can conduct a load test if you have a standard multimeter available. This test helps determine the remaining capacity of your ATV battery.

Learn how to do this simple test and more in your guide on how to test an ATV battery.

Is Your ATV Battery Bad? 9 Symptoms to Look For