Modern ATVs with multiple power-hungry features and accessories can draw more power than the stock battery can handle. One of the more common suggestions for increasing battery capacity involves replacing or supplementing the stock battery with an ordinary car battery.

But can an ATV even handle an automotive battery, and are there any better alternatives?

While it is technically possible to use a car battery on an ATV or UTV, given it’s the same voltage and wired correctly, it is not a solution for everyone. Potential issues include fitment, added weight, and low vehicle charging capacity.

Other ways of increasing the battery capacity are:

Replacing the stock battery with a larger ATV battery.
Installing an extra ATV battery in a dual battery setup.
Installing a high output stator.

This post covers the pros, cons, and other things you need to know if you consider using a car battery on your ATV.

Why Don’t the Stock ATV Batteries Have More Power?

A bigger battery of the same battery chemistry and cell type typically has a higher capacity than a smaller one. And as you probably know, ATV batteries are not as big as car batteries.

On ATVs, space is limited, and keeping the vehicle as light as possible is essential for optimal performance and handling.

That is why ATV manufacturers choose batteries that are just barely big enough to start the engine and operate its primary electric features.

If you do a lot of winching and plowing or use power-hungry accessories like a heated seat or a sound system, you can quickly drain the relatively small battery.

Only 30-60 minutes of plowing or a couple of intensive winching sessions can drain a stock battery to the point where the ATV will no longer start.

To make matters worse, ATVs have relatively low charge output charging systems. ATVs use stators instead of alternators like most cars use. ATVs use stators and not alternators like cars because alternators depend on constant airflow for cooling and are more prone to damage from water and debris.

A modern ATV is packed with components that need electricity to operate. Some examples include an electric fuel pump and fuel injection, an electric control module, an electric shift transmission, an instrument panel, and power steering.

The ATV runs off the electricity from its charging system during regular operation. But when you use more power than the chagrin system can provide, it begins tapping into the power stored in the battery.

The stator and charging system are sized by how much power the ATV needs to run but typically doesn’t have much to spare.

Let’s say a winching session takes the battery down to 80%. The ATV needs quite some time to charge it back up. If you use the winch again before the battery is fully charged, the battery will be at an even lower state of charge when you are done winching.

When you use more power than the stator can produce, eventually, the battery will become discharged entirely.

Benefits of Installing a Car Battery in an ATV

Installing a higher capacity does have its benefits, but it is essential that you also understand its limitations.

Batteries are like storage tanks for electrical power, and their power storing capacity is measured in Amp-hours (Ah).

Amp, or amperage, is a measurement of current, and amp-hours is a measurement of how much current the battery can provide over time.

An ATV battery is typically around 20Ah, whereas a car battery can be around 100Ah or more.

A bigger-capacity car battery discharges at the same rate as a smaller-capacity ATV battery, but with its larger capacity, it will last longer before it dies.

However, as long as you use more power than the ATV charging system can replace, a bigger battery will eventually drain out, just like the smaller one. It just takes more time.

As a battery drains, the voltage drops until it eventually reaches a level where the ATV will not operate properly.

The main benefit of installing a bigger capacity battery is how it provides a bigger buffer against large voltage drops through sessions with high power consumption, typically winching or plowing.

But when stereo systems, lights, hand warmers, and seat heaters drain the battery over time, installing a car battery will only buy you some more time.

Disadvantages of Using a Car Battery in an ATV

Installing a large car battery to your ATV or UTV doesn’t come without its downsides and potential pitfalls.

Incorrect battery installation can damage the ATV. While it is possible to use a car battery on an ATV without damaging it, installing it wrong can cause severe damage like fried wires, a burnt-out stator, or other electronics.

You probably need to use an external charger. While a car battery enhances overall capacity, the power you use must be replenished, or the battery will discharge.

The ATV’s built-in charging system can theoretically charge a depleted car battery, but this process can be slow due to its lower charging output.

In situations where you heavily utilize the car battery’s power reserve, it’s advisable to connect it to an external charger once you’re back home instead of depending solely on the ATV’s charging system to recharge the larger battery.

A large car battery is more challenging to fit. Most ATVs and UTVs don’t have room for a car battery in its usual mounting locations. Typically, you must build a custom bracket or mount the battery on the cargo racks.

A car battery weighs more. Adding too much weight to your ATV will hurt performance and maneuverability. Installing a heavy car battery on the cargo racks can make the vehicle more top-heavy and prone to tipping.

A car battery costs more. While the cost difference is not substantial, it might be a factor to consider if you’re on a budget.

Upgrading the Stock Battery vs. Adding an Extra Battery

There are two approaches to using a car battery on your ATV or UTV.

Replace the stock battery with a car battery.
Connect the car battery to supplement the stock in a dual battery setup.

Replacing the stock battery is the least complicated alternative, as it only requires finding a suitable mounting spot and possibly replacing the stock battery wires. It gives you a bigger buffer, but that’s about it.

Choosing a dual battery setup adds to the complexity of the installation and costs a bit more.

The main difference is that you must add a battery isolator or a battery separator to manage the power distribution to and from the two batteries.

However, a dual battery setup will provide additional benefits when wired correctly.

If you connect the most power-hungry accessories to the auxiliary battery, in this case, a car battery, a massive winching session will not drain the main battery. That way, you won’t have to worry about insufficient power to start and operate the ATV.

It can also help prevent erratic shifting from a voltage-sensitive electric-shift transmission, misfiring from poor ignition, and low voltage error codes from the ECU.

Connecting aftermarket accessories to the auxiliary battery also helps reduce the risk of parasitic drain from the main battery.

Can a Car Battery Damage the ATV Charging System?

Stators and ATV charging systems have significantly developed throughout the last few decades. While some stators can handle a higher-capacity battery without problems, others may overheat and burn out. Older stators are more likely to fail than newer ones.

Most modern stators are designed to handle high current loads from things like winching, but only for shorter periods.

A bad battery with an internal short or trying to charge a drained, oversized battery can draw a considerable amount of current.

The heavy current load causes the stator windings to heat up, which can burn off the insulation coating, creating a short to ground.

That is where a battery separator comes in handy—more on how a battery separator can protect the charging system further down.

How to Install a Car Battery on Your ATV or UTV

This should not be considered a complete installation guide, but I’ve collected some fundamental guidelines to consider to ensure a safe and functioning installation.

Caution: Do not attempt this if you are not confident you know what you are doing. Working with electrics can be dangerous and may damage the ATV. Always wear eye protection when working with batteries.

Plan the Wiring

Single battery: If you’re swapping your ATV’s standard battery for a car battery, you may need to change the wires and wire connectors.

It’s important to remember that if you move the battery to a different location and need longer wires, these wires may also need to be thicker.

The appropriate wire gauge depends on the amount of electrical current (Amps) drawn and the length of the wire.

To determine the correct wire gauge, refer to a wire gauge chart, using your ATV’s original wire gauge and length as a starting point. If you’re uncertain about the correct wire to use, it’s advisable to consult an electrician for expert advice.

Dual battery: If you’re planning a dual battery installation, you must connect the batteries in parallel and not in series. Connecting two batteries in series will double the voltage from 12V to 24V, which can fry the wiring and electrical components on the ATV.

Choose Between a Battery Isolator or a Battery Separator

When planning a dual battery setup, you must also decide whether to use a battery separator or a battery isolator to manage the power distribution between the two batteries.

Connecting a second auxiliary battery directly to the stock battery should be avoided.

If the auxiliary battery becomes weak or goes bad, it will drain a charge from the main battery, potentially leaving both batteries dead. A direct connection can also cause the charging system to over-charge the healthy battery if one of the batteries goes bad.

Battery Isolator

It works like a power splitter with one-way valves (diodes) that prevent current from flowing from one battery to the other.
Simultaneously charges both batteries without connecting the battery terminals in parallel.
Allows the auxiliary battery to drain without draining the main battery.
Diode-type isolators add a small voltage drop in the circuit between the charging system and the batteries.

Battery Separator

It is a more advanced solution than a battery isolator. Sometimes called smart battery isolators. Bi-directional with a built-in circuit board that directs electricity based on voltage readings.
A battery separator allows prioritized battery charging, which ensures the main battery reaches a full charge before it switches to charge the auxiliary battery.
Charges both batteries when the overall current draw is low.
A battery separator prevents charge system overload by disconnecting the auxiliary battery from the charging circuit if the charging voltage drops below 12.8V. A drop in the charging voltage indicates that the current draw is more significant than the charging system is designed to handle. This helps prevent heat buildup and overloading the charging system.
Separates the batteries when they are not being charged.
It can be wired into the ignition so that the auxiliary battery helps start the vehicle if the main battery is low.
The main disadvantage of installing a separator is that it prevents an external charger from charging both batteries.

Both units are about the size of a solenoid and should be installed somewhere protected from dirt and water.

Whichever solution you choose, ensure you get a unit matching your specific vehicle charging output.

What to Connect to the Auxiliary vs. Main Battery

Finally, you must determine what you want to connect directly to the auxiliary battery and what should remain connected to the main battery.

Most of the time, it’s a good idea to connect the winch and other non-essential yet power-hungry accessories to the auxiliary. Things essential for vehicle starting and operation should remain connected to the main battery.

This reduces the strain on the stator and ensures you always have enough battery power to ride back home.

Where to Mount the Car Battery?

Most ATVs and UTVs are not designed to fit a large car battery. You might find a good spot on some models at the back of the frame. Just ensure you keep it safe from heat and moving parts.

Always use a battery box to protect the battery from impacts and short circuits.

If you’re adding an extra battery for plowing, you might want to attach a battery box to the rear cargo rack. That way, you can easily remove the batter outside of the plowing season, and the added weight can help improve traction in the snow.

Generally, it would be best to mount the car battery as close as possible to the original. Longer battery wires will make the ATV charging system work harder due to the wiring resistance.

What Are the Alternatives to Installing a Car Battery?

Installing a car battery to increase battery capacity can be too extreme and inconvenient unless you’re plowing driveways for a living and using the winch all day.

Upgrade the Stock Battery

Many ATV and UTV manufacturers offer battery upgrades with batteries that are larger than stock but not as extreme as full-size car batteries.

A battery upgrade will typically increase the capacity by 20-30%. This is often enough for most ATV and UTV owners looking to upgrade their battery capacity.

Before you order a new battery, ensure the ATV can accommodate the physical size of the slightly larger battery.

Install a Second ATV Battery

Consider installing a second ATV battery in a dual-battery configuration if a single battery upgrade is insufficient.

It is easier to find room for a second ATV battery than a car battery, and it doesn’t weigh as much. Also, the charging system can better keep both batteries charged. Remember to use a battery isolator or separator, as described above.

Upgrade to a High-Output Stator

High-output stators are aftermarket kits designed to increase the ATV charge output. The main benefit of upgrading the stator is that it will charge the battery faster, whether running a stock battery or a higher-capacity battery setup.

Can You Use a Car Battery on an ATV or UTV?