Car Batteries Group Size: How To Check Car Battery Size?

The battery in your car is an essential part of the car. It assists with starting the engine and powers all the electrical systems onboard. With modern vehicles that utilize every bit of space within the engine bay, choosing the correct battery type for your vehicle becomes essential. According to recent statistics, there were more than 16.5 million active electric vehicles worldwide by the start of 2022, which further reduces the flexibility of compatible batteries.

The car battery group size is a significant aspect that can trouble most car owners, especially those who don’t know much about automobiles. Getting it wrong for your vehicle can lead to several unintended consequences. If you want to have a snug fit for your car battery, then this is just the guide for you. We’ll look into the various parameters that determine the appropriate car battery group size for your vehicle and how you can find the correct specifications for your vehicle type.

What Do You Mean By The Group Size for a Car Battery?

The car battery group size determines the vehicle classes the battery fits without additional adjustments. It’s a convenient system designed to inform the customers about the size specifications of the battery, making it more convenient to take one look at the box instead of physically measuring the battery. It typically consists of a single two-digit numeral, with an alphabet added as a modifier for special classes.

Three types of group size classifications are utilized for batteries worldwide. In North and South America, the BCI (Battery Council International) system is denoted as mentioned above. The JIS (Japanese Industrial Standard) is more specific with 6-digit serial numbers and is popular in most Asian countries. It accounts for the extensive variations, as even neighboring countries can have different battery sizes for a vehicle of otherwise similar specs.

Most continental manufacturers, including the UK, accept the German DIN (Deutsche Institut für Normung) in Europe. Despite the localization, many of the serial numbers in the battery group size standards overlap with each other. For example, a car battery belonging to the H6 group under the DIN is the same as the Group 48 battery from the BCI.

Note: The group size doesn’t indicate how big the battery actually is. It’s just a class that denotes which vehicle classes suit the battery. For reference, a Group 73 battery is smaller than a Group 35 battery.

What Does Group Size Mean for Car Batteries?

Group size is designed for a given volume within the engine compartment. It denotes the precise measurements of the battery’s length, width, and height. The length is measured along the positive and negative terminals, while the width is how broad the battery is from a top view. The height of the battery is the distance between the top lid and the base of the casing.

The group size also conveys the placement of the terminals. For instance, a Group 24 battery has terminals emerging from the top of the battery. On the other hand, a Group 24F battery is a flat-top variant with terminals placed along the side of the battery.

What Are the Different Battery Group Sizes?

Considering the BCI configuration of batteries, several group sizes for batteries of various features are available online or at your nearest electronics store. A few of the most popular ones include the ones in the table below.

Group Size Dimensions (LxWxH) (in.) Terminal Placement Vehicle Class
24 10 1/4 x 6 13/16 x 8 7/8 Top RVs, buses, and trailers
24F 10 3/4 x 6 13/16 x 9 Side Family saloons, bikes, and boats
25 9 1/16 x 6 7/8 x 8 7/8 Top Large sedans and midsize pickups
34 10 1/4 x 6 13/16 x 8 7/8 Top Boats, motorhomes, and caravans
35 9 1/16 x 6 7/8 x 8 7/8 Top Small hatchbacks and sedans
51 9 3/8 x 5 1/16 x 8 13/16 Top Sports cars and luxury coupes
51R 9 3/8 x 5 1/16 x 8 13/16 Top reversed Sports cars, SUVs, and full-size pickups
52 7 5/16 x 5 13/16 x 8 1/4 Top ATVs, crossovers, and marine vehicles
58 10 1/16 x 7 3/16 x 6 15/16 Top Family saloons, small SUVs, and speedboats
58R 10 1/16 x 7 3/16 x 6 15/16 Top, reversed Midsize sedans, crossovers, and large hatchbacks
59 10 1/16 x 7 5/8 x 7 3/4 Top Full-size SUVs and luxury sedans
65 12 1/16 x 7 1/2 x 7 9/16 Top Sports cars and large coupes
78 10 9/10 x 7 x 7 Side Large SUVs, Minivans, and RVs

How To Check Car Battery Size?

Car Batteries Group Size 1

There are several ways to check which car battery group size fits your vehicle. You can examine the rating on the packaging or the owner’s manual. It’s also mandatory for manufacturers to state all compatible group sizes on the battery itself. If all of those are illegible, you can research the model number of the battery online or measure the dimensions yourself and compare them to the chart described above.

Steps to Identifying Your Car’s Battery Group Size

No one expects you to take one glance and realize which group size your car’s battery belongs to. You can take a few steps to identify your car’s battery group size. Those include the following.

  • For a factory-installed battery, turn off the engine and disconnect the battery from the terminals. Safely remove it from the engine bay and put it on a flat, insulated surface. Observe the group size number that may be located at the bottom, top, or sides. If the numbers are illegible, you may need to clean the battery with a mildly basic solution.
  • In case you need to determine the group size of a battery off-the-shelf, check the packaging or the owner’s manual. You can also ask the shopkeeper to provide a sample to determine the battery group size.

How to Determine Your Car’s Battery Specifications

In addition to the battery group size, there are also other criteria to ensure that you have the battery to suit your requirements. A few prominent ones are listed below.


The voltage is the potential difference between the positive and negative terminals of the battery. It’s usually higher than what’s rated on the packaging. If you buy a new 12V battery and check the voltage using a multimeter, it is often above 13 Volts.

Reserve Capacity

It denotes the duration for which the battery can supply a constant current to the circuit at full load. The reserve capacity is usually measured in minutes and conveys the energy stored within the battery at room temperature.

Cold Cranking Amps (CCA)

The CCA rating signifies the maximum current that a battery can deliver at 0°F (-17.77°C). It’s a required metric for vehicles likely to encounter harsh conditions, such as SUVs and snowmobiles.


The method of storing and supplying electrical energy can determine your battery’s lifespan and maintenance cycles. Flooded lead-acid batteries were quite popular a few years ago, with AGM batteries replacing them for most vehicles. Today, HEVs operate with Silver-calcium batteries, and Li-ion versions are observed in fully electric vehicles.

Importance of Getting the Correct Battery Group Size

It’s necessary to get the battery group size correct for the following reasons.

  • A loose battery can slide around the engine compartment, ruining the electricals or breaking other sensitive components.
  • The battery group size denotes the location of terminals. Misconnecting the terminals can result in a short circuit or strain of the terminals, causing an electrical wire.
  • An incorrect battery group size may cause your battery to overheat or come in contact with other metal components, giving a fatal shock to anyone who touches the body of the car.

The Most Common Car Battery Sizes

Depending on the classification accepted within your country, there are several group battery sizes. The most common car battery sizes for BCI specs include Groups 24, 24F, 35, 51, 58, and 65.

Frequently Asked Questions

What if I Use the Wrong Group Size For a Battery?

A wrong battery group size may be too big for the compartment or slide around during the drive in case it’s too loose. Moreover, inappropriately connecting the terminals may result in an electrical fire.

Does Car Battery Group Size Matter?

Yes. The car battery group size lets the owner know which batteries can fit within the engine bay.

Are All Car Batteries the Same Size?

No. Most car batteries belong to a specific group size, depending on their dimensions.

Can You Use a Different Group Size Battery?

It depends upon the dimensions and placement of battery terminals. For example, a Group 78 battery is compatible with a Group 37F battery bay.


Determining your car battery group size is essential to choose the suitable variant for your vehicle. We hope this guide grants you additional insights into the process and helps you along the next time you need a battery replacement.


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