Home FAQ

How do I tell my car battery size?

The quickest way to tell your car battery size is to read the Group Size stamped on the battery label (for example, Group 24F). If the label is worn or unreadable, your vehicle’s manual or a VIN-based lookup at a dealership or parts retailer will also confirm the correct size.

Read the battery label for the Group Size

Direct access to the battery itself is the most reliable starting point. The Group Size code on the label determines the physical fit, including dimensions and terminal layout.

What to look for on the label

Group Size code (e.g., 24F, 35, 48, etc.)

Terminal configuration and polarity noted on or near the label

Other specs such as CCA (cold cranking amps) and RC (reserve capacity) that accompany the size

Conclusion: The Group Size on the battery label is the quickest, most reliable indicator for matching your vehicle. If the label is unreadable, proceed to use official sources or VIN lookups described below.

Consult official sources or VIN lookup

If the label isn’t readable, turn to your vehicle’s documentation or a VIN-based lookup to confirm the exact size recommended for your model.

Owner's manual and engine bay placards

Check the manual’s battery or electrical system section for the recommended Group Size

Look for a sticker in the engine bay or near the battery tray listing the group size

Note that some manufacturers provide a part number rather than the code alone; you can cross-reference with catalogs

Conclusion: Manuals and engine bay placards provide the manufacturer’s official size specification and help ensure the battery will fit your mounting brackets and cable layout.

VIN-based lookup and dealer resources

Enter your VIN on the official dealer parts site or a reputable online catalog

Retrieve the recommended group size and compatible battery options for your exact model

Verify fit by cross-checking tray dimensions and terminal orientation

Conclusion: VIN-based lookups are especially useful for newer or less common configurations; always confirm fit before purchase.

Physical fit checks (backup method)

As a backup, you can measure the battery tray and compare with common group size dimensions to ensure a proper physical fit, including cable reach and terminal placement.

How to measure and compare

Measure tray length, width, and available height

Compare with standard group size specifications from reputable catalogs

Ensure the battery’s terminal positions align with the cables and clamps and that it sits securely

Conclusion: Physical measurements are a helpful backup when replacing older or unusual vehicles; they should confirm the chosen group size rather than replace it.

Summary

In practice, start with the battery’s Group Size on the label. If that is unreadable, consult the owner's manual or use a VIN-based lookup through a dealer or trusted parts retailer to confirm the exact size. Always verify that the replacement battery matches the group size, CCA, RC, terminal layout, and fits the tray for a safe, reliable installation.

How do I know what size my car battery is?

You can find your car battery's size by checking the BCI Group Size number printed on the battery's label or in your vehicle's owner's manual. If you can't find the label, you can measure the battery or look up the specifications online using your car's make and model.
Where to look for the battery size
This video explains how to find battery information on the battery label and other ratings: 55sGS Yuasa UKYouTube · Feb 8, 2023

On the battery itself: Look for a sticker on the top or side of the battery case. The BCI group size is usually a two-digit number, sometimes followed by a letter (e.g., 24F, 35, or 65).
In the owner's manual: The correct battery size and other specifications are listed in your car's owner's manual.
Online: Many auto parts websites have a "battery finder" tool where you can enter your vehicle's year, make, and model to find compatible batteries.

If you can't find the information

Measure the battery: If the label is missing or unreadable, you can measure the physical dimensions (length, width, and height) of the battery. You can then use these measurements with a BCI group size chart to find the correct size, says JEGS High Performance.
Ask a professional: Take the car to an auto parts store or dealership, and they can determine the correct battery size for you.

Important considerations

The BCI group size ensures the battery has the correct physical dimensions to fit properly in your car's battery tray and under the hold-down bracket.
It also indicates the terminal post location and orientation, which is crucial for the battery cables to reach correctly, notes Battery Guyz.
In addition to the size, make sure the new battery meets the required specifications for Cold Cranking Amps (CCA), which is especially important for starting the car in cold weather, say Battery Guyz and JEGS High Performance.

Is a car battery 12 V or 24 V?

Most passenger cars use a 12V battery, while heavy-duty vehicles like large trucks typically use 24V systems. Standard car batteries are 12V because they are made of six 2V cells wired together, and the electrical components in most cars are designed to run on 12V.
12V batteries

Common in: Passenger cars, RVs, and boats.
Why: The 12V system is the established standard because it requires less copper than a 24V system for power transmission, and the electrical components, like the starter and lights, are designed for this voltage.
Construction: A 12V battery is made of six lead-acid cells, each producing about 2 volts, arranged in series.

24V batteries

Common in: Large trucks, commercial vehicles, and some industrial or military equipment.
Why: These vehicles have high-compression diesel engines that require more powerful starters, which are more efficient with a 24V system.
Construction: A 24V system often uses two 12V batteries wired in series, or a single battery with 12 cells.

How to identify the size of a battery?

You can check a battery's size by looking for markings like mAh, Wh, or a BCI Group Size on the battery itself, in the device's user manual, or by using online tools. For digital devices, you can often find the battery capacity in the device's settings under an "About" or "Battery" section. For car batteries, the physical group size is printed on the battery's label and is crucial for ensuring a correct fit in the car's compartment.
This video demonstrates how to find battery information on an Android phone: 58sWiz of AppsYouTube · Apr 3, 2024
For portable electronics

Check the label: Look for markings like mAh (milliampere-hours) or Wh (watt-hours) printed on the battery itself.
Check the device settings: On many Android devices, you can find battery capacity in Settings > About phone > Battery or by searching for "battery information".
Check the manual: The device's user manual will list the battery capacity or type.

For car batteries

Check the battery label: Open the hood and look for the BCI Group Size printed on the label on top of the battery. This size is crucial for ensuring a physical fit in the car.
Check the owner's manual: The owner's manual will specify the correct BCI Group Size and other details like cold cranking amps (CCA).
Use online tools: Many auto parts stores offer online fitment finders where you can enter your car's year, make, and model to find compatible batteries.
Measure it yourself: While less reliable than the BCI size, you can measure the length, width, and height of the battery itself and compare them to online charts to find a corresponding group size.

This video demonstrates how to test a car battery using a multimeter: 59sClassic Car MaintenanceYouTube · May 31, 2024

What does 24f mean on a battery?

The "24F" on a battery indicates its BCI group size, which is a standard for physical dimensions and, most importantly, the terminal configuration. The "24" refers to the battery's size, while the "F" signifies that it has a front-terminal layout, meaning the positive and negative terminals are reversed compared to a standard Group 24 battery. This reversed layout is crucial for correct installation in a vehicle, as the battery cables are designed to reach a specific terminal position.

Key differences and implications

Terminal placement: A standard Group 24 battery has the positive terminal on the left and the negative on the right when viewed from the top. A Group 24F battery has the terminals reversed, with the positive (+) terminal on the right and the negative (-) on the left.
Vehicle compatibility: The "F" designation is critical because car battery cables are fixed in length and position. Using the wrong group size will make it difficult or impossible to connect the cables correctly, potentially leading to poor connections, cable strain, or damage to the vehicle's electronics.
Dimensions: While the overall physical size is similar to other Group 24 batteries, specific dimensions can vary slightly, so it's always best to check the exact specifications for your vehicle.
Other group size variations: Other letters can be added to the group number to indicate different features, such as "R" for reverse terminal orientation, "H" for higher cranking amps, or "T" for enhanced terminal features.

Kevin Bennett

Company Owner

Kevin Bennet is the founder and owner of Kevin's Autos, a leading automotive service provider in Australia. With a deep commitment to customer satisfaction and years of industry expertise, Kevin uses his blog to answer the most common questions posed by his customers. From maintenance tips to troubleshooting advice, Kevin's articles are designed to empower drivers with the knowledge they need to keep their vehicles running smoothly and safely.