What Size is a Riding Lawn Mower Battery?

You’re ready to tackle your yard, but your riding lawn mower won’t start. The engine sputters, coughs, and then falls silent. You check the fuel, the spark plugs, and even the air filter, but nothing seems to be amiss. Finally, you realize it’s the battery. But what size battery does your mower need?

This article will guide you through understanding riding lawn mower battery sizes, the common types available, and how to choose the right one for your specific machine. We’ll also cover how to test your battery, ensure proper installation, and even discuss battery maintenance to keep your lawn mower running smoothly. Let’s get started!

What Size is a Riding Lawn Mower Battery?

The size of a riding lawn mower battery is typically measured in group sizes, which indicate the overall dimensions and terminal configuration. There are several standard group sizes, including Group 24, 24F, 25, 27, and 29. The most common group size for riding lawn mowers is Group 24, but it’s always best to check your owner’s manual for the specific battery recommendation.

Understanding Battery Group Sizes

The group size designation provides a standardized way of identifying battery dimensions and terminal configurations. While different manufacturers may use the same group size, slight variations might exist, so it’s crucial to confirm the compatibility before making a purchase.

Identifying Your Battery Group Size

The most accurate way to determine your riding lawn mower’s battery group size is by consulting the owner’s manual. It will typically specify the recommended group size and other important details. If you can’t locate the manual, the battery itself might have a sticker or label with the group size information.

Common Battery Group Sizes for Riding Lawn Mowers

  • Group 24: This is the most common group size for riding lawn mowers, offering a good balance of capacity and size.
  • Group 24F: This group is similar to Group 24 but has a different terminal configuration.
  • Group 25: Slightly larger than Group 24, providing increased capacity.
  • Group 27: Offers even more capacity than Group 25, suitable for larger or high-performance mowers.
  • Group 29: The largest group size commonly found in riding lawn mowers, offering maximum capacity but requiring more space.

Beyond Group Size: Other Important Battery Specifications

While group size is essential, several other specifications influence battery performance and compatibility:

1. Voltage

The voltage rating indicates the electrical potential of the battery. Riding lawn mower batteries typically have a 12-volt rating, which is essential for starting and powering the engine.

2. Cold Cranking Amps (CCA)

CCA indicates the amount of current the battery can deliver at a freezing temperature (0°F/-18°C) for 30 seconds. Higher CCA ratings are crucial for starting the engine in cold weather. Choose a battery with sufficient CCA for your location and the time of year you will be using the mower.

3. Reserve Capacity (RC)

RC measures the battery’s ability to provide power in a reserve situation. It is expressed in minutes and indicates how long the battery can supply power at a rate of 25 amps while maintaining a minimum voltage of 10.5 volts. A higher RC is beneficial for riding lawn mowers with extended run times or those equipped with additional accessories.

4. Terminal Configuration

Battery terminals determine how the battery connects to the mower’s electrical system. Check your owner’s manual or existing battery to confirm the correct terminal configuration (e.g., top post, side post, etc.).

Choosing the Right Battery for Your Riding Lawn Mower

When selecting a replacement battery for your riding lawn mower, consider these factors:

  • Battery Group Size: Ensure the battery group size matches the one specified in your owner’s manual.
  • Cold Cranking Amps: Choose a battery with sufficient CCA for your climate and usage needs.
  • Reserve Capacity: Select a battery with adequate RC for your mower’s power requirements and accessories.
  • Terminal Configuration: Confirm the battery has the correct terminal configuration for your riding lawn mower.
  • Brand and Warranty: Look for reputable brands with reliable performance and good warranty coverage.

Maintaining Your Riding Lawn Mower Battery

A well-maintained battery will deliver optimal performance and extend its lifespan. Here are some tips for keeping your riding lawn mower battery in good working order:

  • Keep the Battery Terminals Clean: Corrosion can hinder electrical conductivity, so clean the terminals regularly with a wire brush or battery terminal cleaner.
  • Check the Battery Fluid Level: If your battery has removable caps, check the fluid level and add distilled water if needed.
  • Avoid Deep Discharges: Deep discharges can shorten battery life, so avoid letting the battery fully discharge. If your mower hasn’t been used for a while, charge the battery before attempting to start it.
  • Store the Battery Properly: When not in use, store the battery in a cool, dry place, and recharge it every few months to prevent sulfation.


Finding the right size battery for your riding lawn mower is crucial for ensuring reliable starting and performance. By understanding the key specifications like group size, CCA, RC, and terminal configuration, you can confidently choose a battery that meets your mower’s needs. Regular battery maintenance will help extend its lifespan and prevent unexpected breakdowns.


1. What are the common sizes of riding lawn mower batteries?

The most common sizes for riding lawn mower batteries are Group 24, Group 25, and Group 27. These sizes are often used in tractors, ATVs, and other heavy-duty equipment. The Group number refers to the battery’s physical dimensions, including height, width, and length.

Choosing the correct size is crucial for proper fit and performance. It’s important to check your owner’s manual or the battery compartment to confirm the recommended battery size for your specific mower model.

2. What does “Group” refer to in a riding lawn mower battery size?

The “Group” designation for riding lawn mower batteries refers to a standard classification system that defines the battery’s physical dimensions. This system helps ensure compatibility between different batteries and equipment.

Each Group number represents specific height, width, and length measurements. For example, a Group 24 battery has a different size than a Group 27 battery.

3. How do I know what size battery I need for my riding lawn mower?

The easiest way to determine the correct battery size for your riding lawn mower is to consult your owner’s manual. The manual will specify the recommended battery size and type for your mower model.

You can also check the battery compartment of your mower to see what size battery is currently installed. If you are unsure, it is always best to contact the manufacturer or a qualified technician for assistance.

4. Can I use a different size battery in my riding lawn mower?

While it is possible to use a different size battery, it is generally not recommended. Using a battery with a different size could lead to compatibility issues, such as improper fit, electrical problems, or reduced performance.

It is always best to use the recommended battery size for your mower model to ensure optimal performance and longevity.

5. Are all Group 24 batteries the same?

Although batteries labeled as Group 24 have the same physical dimensions, they may have different specifications, such as cold cranking amps (CCA) and reserve capacity.

CCA measures the battery’s ability to start the engine in cold weather, while reserve capacity indicates how long the battery can provide power without being recharged. Therefore, it’s important to choose a Group 24 battery with the appropriate CCA and reserve capacity for your mower.

6. What are some of the factors to consider when choosing a riding lawn mower battery?

When selecting a riding lawn mower battery, it’s crucial to consider factors like battery size, cold cranking amps (CCA), reserve capacity, and type (e.g., flooded, AGM, or gel).

You should also consider the battery’s warranty, brand reputation, and price. It’s advisable to consult your owner’s manual or a knowledgeable technician for guidance.

7. How often should I replace my riding lawn mower battery?

The lifespan of a riding lawn mower battery can vary depending on factors like usage, climate, and maintenance.

However, most batteries will need replacement after 3-5 years. Signs of a failing battery include slow cranking, frequent recharging, or a swollen or leaking battery case. Regular maintenance, such as keeping the battery terminals clean and checking the electrolyte level, can help extend its lifespan.

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