If you own a car, then you’ve probably faced that scenario where the car lost power unexpectedly. If I’m not wrong, this happened most probably in the morning when you were getting ready for work. Although you must have jump-started the battery using your neighbor’s battery, the first thing you did after getting to work was to find a replacement battery. After searching all over the internet, things get sour when you get buried in a world of technical jargon such as volts, amps, and car battery group size.
You see, when you search the internet, there is plenty of content that discusses how to choose a battery. Most of them talk about the size, brand, age, reverse capacity, and cold-cranking amps. Unfortunately, most of these guides fail to discuss battery group size in detail.
So, in this short guide, we’re going to compile the available pieces of information that are available to give you a solid understanding of what car battery size means and how it impacts your decision.
What is Car Battery Group Size and Why Does it Matter?
When it comes to batteries, size is one of the factors that directly influence your decision. To help you determine the right battery size, the Battery Council International (BCI) has created a battery group size chart that provides battery information such as the physical dimensions in inches and millimeters.
With this information, you can easily determine the correct size of a battery that will be compatible with your specific vehicle. For instance, if you fit a large truck battery in your 2-door vehicle, the battery will be too large to fit in the small battery compartment.
On the other hand, if you fit a tiny battery in your utility truck, the battery will most likely shift from left to right when driving causing sparks or a possible short circuit. It’s also likely to scrap your hood causing potential damage.
So, Which are the Different Car Battery Groups?
As we’ve already mentioned, car battery size is an industry-standard that describes a battery’s size in terms of the physical dimensions and the position of the terminals also known as the polarity. So, when buying a new battery, you have to confirm the dimensions (the length, width, and height) and the position of the terminals.
Thankfully, you don’t need to use a measuring tape just to measure the dimensions of a battery. Most batteries have a printed label that notifies you of their sizes. Also, your car’s manual has all the information about the type of battery you need to get. With that in mind, here are three major battery groups you need to be aware of.
Side Post Batteries
Just as the name suggests, side post batteries have their posts bolted on the side of the battery leaving the top section smooth. This type of battery setup is used by most General Motors vehicles as it helps to reduce the chances of corrosion on the battery terminals. Battery group sizes that use the side post-setup are 70, 74, 75, and 78.
Standard Top Post Batteries
This battery group is exactly what you see when you think of a typical car battery. The posts protrude at the top of the battery making the connection easier. Most Japanese and American cars, trucks, and SUVs use this type of battery configuration making it very common among most motorists. Battery group sizes that use the top post configuration include 24, 24F, 25, 34, 35, 51, 51R, 52, 58, 58R, 59, and 65.
Recessed Top Post Batteries
Recessed top post batteries are less common as compared to standard top post batteries. They’re mostly used by major European carmakers such as BMW, Mercedes, Audi, and Volkswagen. With this type of battery, the posts are recessed on the far corners of the battery. Instead of protruding upwards, these posts sit flush with the top of the battery. Among the batteries that use this setup include 41, 42, 47, 48, and 49.
Car Battery Sizes
Other than checking your car’s manual, another source where you can find credible information about your car’s battery size is a battery group size chart. This is available online. Here, you’ll find so many battery sizes that are available.
Bu, although the chart contains so many battery sizes, all these can be simplified into 4 basic group sizes. You see, the reason why most people are confused when it comes to battery sizes is that too many terms are used to describe just one battery size.
For instance, the typical BCI battery group sizes used in the US are quite different from what is used in Europe yet they refer to the same size. So, with that said, let’s discuss the four major battery group sizes.
“H” Series
Batteries using the H series configuration are known to have the same width and height. The only thing that changes is the length of the battery. These batteries range from H5, H6, H7, and H8. They’re also the most common type of battery sizes found in a majority of European and American modern cars. Other terms that refer to these battery sizes include;
- H5 is also known as Group 47
- H6 is also known as Group 48
- H7 is also known as Group 94R
- H8 is also known as Group 49
T Series
These types of batteries are very similar to our previous H series only that they’re ¾ inches (17mm) shorter in height. These battery sizes are also used in most European cars though not as often as the H sizes. They’re available in the T5 and T6 sizes where T5 is also referred to as 94R and T6 is also called L2.
35 and 51R
35 is a battery size that’s commonly used by most Japanese cars such as Nissan, Toyota, Mitsubishi, and Subaru. This group is also called Q85 and is also very common among older US vehicles. 35-battery size is also compatible with group 24 batteries only that it’s 1-inch shorter in length.
On the other hand, group 51R is regarded as a lighter and smaller version of the 35-battery size. Since it’s a little bit narrower, this battery size is used in most Honda and GTR vehicles.
24 and 27
Lastly, groups 24 and 27 are common in older versions of American cars. They’re also found in some Honda, GM vehicles and are often used in boats. The 24-battery size can be interchanged with group 35 only that it’s 1-inch longer than the latter.
So, other than what we’ve discussed, there are a few other battery sizes that are very common among most American, Japanese, and European vehicles. To give you a clear understanding of these battery sizes, here’s a simple chart you can refer to.
| Group Size | L x W x H (Inches) | L x W x H (Millimeters) |
| 24 | 10 1/4 x 6 13/16 x 8 7/8 | 260 x 173 x 225 |
| 24F | 10 3/4 x 6 13/16 x 9 | 273 x 173 x 229 |
| 25 | 9 1/16 x 6 7/8 x 8 7/8 | 230 x 175 x 225 |
| 34 | 10 1/4 x 6 13/16 x 7 7/8 | 260 x 173 x 200 |
| 35 | 9 1/16 x 6 7/8 x 8 7/8 | 230 x 175 x 225 |
| 51 | 9 3/8 x5 1/16 x 8 13/16 | 238 x 129 x 223 |
| 51R | 9 3/8 x 5 1/16 x 8 13/16 | 238 x 129 x 223 |
| 52 | 7 5/16 x 5 13/16 x 8 1/4 | 186 x 147 x 210 |
| 58 | 10 1/16 x 7 3/16 x 6 15/16 | 255 x 183 x 177 |
| 58R | 10 1/16 x 7 3/16 x 6 15/16 | 255 x 183 x 177 |
| 59 | 10 1/16 x 7 5/8 x 7 3/4 | 255 x 193 x 196 |
| 65 | 12 1/16 x 7 1/2 x 7 9/16 | 306 x 190 x 192 |
Final Verdict
As you can see, there’s a lot to talk about when it comes to car battery sizes. However, when making your choice, you need to stick to your manufacturer’s recommendations to avoid messing up. For instance, if your car uses a recessed top battery and you end up buying a standard top post battery, the protruding posts of the battery can easily get to contact with the car’s hood, which is metallic.
In the process, this can cause sparks that can lead to a fire accident. So, to stay away from such avoidable problems, it’s good that you consult your car’s manual for the type of battery you’ll need.
Other than the battery size, you need to be keen on other factors such as Amp Hours, Cold-Cranking Amps, Reserve Capacity Rating, and Cranking Amps. Although this is a topic for another day, knowing all this technical jargon will make you feel confident when discussing it with your mechanic.
