What Does Group Size Mean On A Battery?

What Does Group Size Mean On A Battery?

The first thing you need to know about batteries is how to tell how many amp hours your battery has in it. This will help you find the best battery for the job.

But what does group size mean? And how do you use the information?

Most people never stop to think about how big the groups are on their battery. But it’s crucial to know before you purchase since bigger groups indicate a more powerful battery, which means it will last longer, be more economical, and cost less to charge.

In this blog post, we’ll cover what does group size mean on a battery? and how you can calculate it. We’ll also show you how to choose the right battery for your car or another device.

What Does Group Size Mean?

For those of us who drive electric vehicles, this is one of those things that’s hard to ignore. When you start thinking about which battery to use, you’ll need to consider several factors. They include size, capacity, price, and most importantly, group size. There are a couple of different organizations that come up with these sizes/groups, including the BCI (which stands for Battery Council International, instead of the IBC) and many of their common sizes include the previously-mentioned Group 34 & 27, as well as the 31 and 35.

The group size refers to the number of amp-hours available in the battery. You get more amp hours when the group size is higher. The maximum amperage rating will also determine the amount of time you can run your vehicle before you need to recharge it.

So what does this mean? It means that a larger battery will run longer before you need to charge it. The more amp-hours available in the battery, the longer it can be used before you need to recharge it. A bigger battery means you have more power for longer periods. some group sizes are the same width and length, but have a lower height

Further, A small group is the one where the highest amp-hours per group is 1 amp-hour or less.

For example, if you have two batteries, one is a 3 amp hour battery and the other is a 4 amp hour battery, the first is a small group and the second is a large group.

A larger group will be able to power more devices at the same time. This is what gives you more options. 

What Does Group Size Mean On A Battery Group Size Chart?

The group size that is shown on a battery group size chart is how many amps the battery will put out over its lifetime (in other words, how many amp-hours). The number of amps that the battery can put out is called its “Ampere-hour capacity.” The higher the Ampere-hour capacity, the longer the battery will last. A battery group size refers to the product’s physical dimensions, including Length, Width, and Height. When replacing the old battery with the new one, be sure that the new battery is of the same chemistry as the old one

For example:

A battery with a 10 amp-hour capacity will put out 10 amps for 1 hour before needing to be recharged, while a battery with a 100 amp-hour capacity will put out 100 amps for 1 hour before needing to be recharged.

Look Up Battery Capacity on a Battery Group Size Chart:

A battery group size chart shows how much charge the battery can hold. If you look at the label, it’ll show the number of amp-hours that the battery can hold before needing to be recharged. To figure this out, you’ll need to divide the capacity by 1000 to get the total number of amps that the battery will put out for an hour. Sticking with the suggested battery negates having to worry about things like the cold cranking amps ( CCA ) and reserve capacity ( RC ).

For example, a battery that’s rated to hold 3 amps can put out 3 amps for 1 hour before needing to be recharged. If it has a rating of 12 amps, then it will put out 12 amps for 1 hour before needing to be recharged. Look up the battery’s ampere-hour capacity on a battery group size chart, and then look up the number of amps that it puts out for an hour to find the total number of amps it will put out over its lifetime. Your vehicle requires a certain amount of amperage to start, especially in cold weather. If your battery doesn’t have sufficient amperage to turn over in cold weather, it won’t start and you’ll be stranded.

Know the Total Capacity of Your Batteries:

Before Buying The total capacity of your batteries is the sum of their capacities, so if you have 4 18650 batteries in series, that’s 72 amp-hours. If you buy only one 18650 battery, you’ll have a maximum of 18 amp-hours.

Be Careful About What You Get:

If you’re not careful about what you buy, you could end up with a lot of extra, useless batteries that you’ll never use. It’s always best to buy as few batteries as possible. To make sure you don’t get a bunch of batteries that you can’t use, make sure you know the size of the batteries before buying them. 

Most online vendors will let you choose a size, but be sure to make a list of what size batteries you need in advance so that you don’t order more than you need. Modern vehicles cram more technology into a more compact space get the wrong sized battery and installation will feel like trying to fit a square block in a round hole.

Group 47 (H5, L2, 55L2) batteries are medium size batteries, mostly used in automotive and known as light industrial batteries applications as cranking or dual-purpose batteries for starting mid-range diesel and gas engines. If you bought the wrong size, the battery does not fit properly in the battery tray or to hold your car battery.

The BCI Group 35 battery is a very popular battery size of lead-acid batteries that are commonly used as a starting or dual-purpose battery in cars, trucks, RVs, and other similar applications. BCI Group 75 batteries are commonly used in cars, light trucks, and other vehicles where they are used to start internal combustion engines but are also used to power various loads such as pumps, winches, lights, etc.

Things To Remember While Shopping For Batteries:

A few things to remember when shopping for batteries:

  • The bigger the number on a battery’s label, the higher the voltage it has. A 1,000 mAh cell will put out about 1 amp for a very short time, while a 3,000 mAh cell will put out 3 amps for a long time.
  • If you have more than one 18650 battery (like those in this example), be sure to know how many volts they are running at, as well as their total capacity. The total capacity of the cells is listed on the back of their labels.
  • Battery voltage is measured by subtracting the voltage of the positive side from the negative side. In other words, if the positive side of a battery is 5.7 volts and the negative side is 6.5 volts, the battery’s voltage is 7.2 volts.
  • Don’t buy batteries that are above your desired capacity. For example, if you want a 1,500 mAh battery, don’t buy batteries that have 2,000 mAh or even 2,500 mAh capacity. You don’t need a 2,500 mAh battery to run an iPhone 6S for 10 hours you need at least one 18650 battery with a 1,500 mAh capacity. Although different batteries can be used interchangeably, it is advisable to use the car manufacturer’s recommended battery. 

What Are Common Battery Group Sizes?

The common group sizes on a car battery are 18V/4Ah, 36V/6Ah, 72V/12Ah, and 144V/24Ah. These four battery groups are also commonly referred to as Amp Hours (Ah).

What Are the Differences Between 18V/4Ah, 36V/6Ah, 72V/12Ah, and 144V/24Ah?

When people say that batteries can last anywhere from 6 hours to several days, they’re referring to the amount of time the battery can power a vehicle. For example, a battery can be used to start a car for about 5 hours. If the car runs for 4 hours, the battery has lasted for about 90% of its capacity. However, it will still be able to start the car again.

If you want to make sure you get your battery’s capacity fully used (so that it can last as long as possible), it is important to know which groups are on your battery. Here is the breakdown of each group:

18V/4Ah:

18 volts and four amperes are used in 18V/4Ah batteries. This group is common in smaller 12-volt batteries. A 12-volt car battery with this group size can power an emergency light for about 3 hours before needing to be recharged.

36V/6Ah:

36 volts and six amperes are used in 36V/6Ah batteries. The average car battery is rated at about 36 volts and 15 amperes. This is also a good group size for larger 12-volt batteries.

72V/12Ah:

72 volts and twelve amperes are used in a 72V/12Ah battery. This is the typical group size of a household refrigerator or deep cycle batteries. It can last an average vehicle for 10 to 12 hours, depending on its load. The second variation is a deep cycle (also known as a marine battery). The battery’s internal construction doesn’t respond well to short bursts of power. If you take the marine battery off the boat, the charging session should last between 14 and 16 hours, reports Battery University. For marine applications, look for group sizes indicating the letter “M.” These batteries are designed for watercraft applications.

144V/24Ah:

144 volts and twenty-four amperes are used in a 144V/24Ah battery. The higher number of amperes indicates a stronger battery, which means it can last longer in a vehicle.

What are Group 24 Batteries?

These are also known as Lithium-ion Batteries or li-ion batteries. Lithium-ion batteries are becoming more popular in a variety of industries as they are the most power-efficient batteries available. Group 24 battery chemistry is AGM (Absorbent Glass Mat) SLA (sealed lead acid) battery, but there are other chemicals/types like gel-cell batteries, flooded batteries, and even lithium-ion batteries. By selecting a group 24 battery, for example, you know the exact size that you’re purchasing.

Side post batteries have cable ends that screw into the side of the battery, as opposed to having battery posts on the top of the battery. Group 24 batteries usually have large UPS systems. Group 24 batteries are mostly general-purpose batteries commonly found in large UPS systems, medical and security systems, wheelchairs, vehicles, industrial applications, etc. These groups are popular with everyone because they are designed for lightweight vehicles.

The Science Behind Lithium-ion Batteries:

Lithium-ion (Li-ion) is the most common type of battery. They are rechargeable and have the highest energy density of any battery currently on the market.

Lithium-ion Batteries in Action:

When talking about the benefits of lithium-ion batteries we often talk about their size and weight. Lithium-ion batteries are much larger than other types of batteries. However, lithium-ion batteries are lighter than other types of batteries and allow you to pack more energy into a smaller volume.

Battery Specifications:

They have a high energy capacity to power devices for longer periods, can be charged more quickly, are lightweight, and can hold a large amount of power in a small package.

What are Group 35 Batteries?

Group 35 batteries are used in some very old or out of production electronic devices, so you’re not going to see them very often. Group 35 batteries work differently than other batteries and don’t get as many recharges. Most batteries won’t last through a single charge. If your device doesn’t state whether it needs group 35 batteries, then it probably won’t need them.

Group 35 batteries are much smaller than other types of batteries. They also require special chargers to keep them alive. These chargers have been discontinued for many years, so you may need to find a replacement online.

The two main types of group 35 batteries that are still in production are:

The Duracell battery is used in everything from smoke detectors to space probes.

The Energizer battery is used in everything from calculators to flashlights.

You can determine which battery is right for you by looking at the manufacturer’s stamp on the battery. It should be stamped with either the name of the company or an image of their product.

WHat Are Group 75 Batteries?

G75 batteries power most of our modern equipment. They’re used in every kind of device imaginable from phones, cars, cameras, computers, appliances, and everything else.

These are the batteries we all use every day, yet few people understand how they work. Let’s take a look at each component of a G75 battery.

Lead Acid Batteries:

There are 2 different types of batteries that use lead-acid chemistry; the “A” cell and the AGM (accumulating growth material) type. There is little difference between these two batteries, as they both produce the same voltage when fully charged. AGM batteries work just like wet cell batteries, without the potential for spilled battery acid.

Lead-acid batteries are made from lead plates encased in an acid electrolyte. Each lead plate is connected to positive and negative terminals, which allow electricity to flow through the battery when it’s fully charged.

Ni-Cd Batteries:

Ni-Cd batteries are also known as NiCD or Ni-Cd batteries are very similar to lead-acid batteries, but they use nickel instead of lead. They have a lower capacity than lead-acid batteries, so they’re commonly used in digital cameras.

This type of battery is very sensitive to water, so if you store your Ni-Cd batteries in wet conditions, you can destroy them.

Zinc-Air Batteries:

Zinc-air batteries are extremely rare, but they’re very powerful. Each zinc-air cell can hold 5 times the amount of energy stored by a lead-acid battery.

There are many types of zinc-air batteries, but they all share one important thing – a positive zinc electrode. The electrode is filled with a solution that contains zinc metal and air. This produces enough oxygen to continuously oxidize the zinc metal and produce electricity.

Lithium-ion Batteries:

Lithium-ion batteries are the most commonly used type of battery in our day-to-day lives. They produce 1/10th the power of Ni-Cd or Zn-air batteries, but they’re much safer. These batteries also have an impressive shelf life when compared to other types of batteries.

Lithium-ion batteries have a negative lithium electrode and a positive carbon electrode. When electricity flows through the battery it causes the lithium to move from the electrode with a negative charge to the positive electrode with a positive charge.

Apart from that, there is another kind known as a Wet cell battery. Some modern wet cell batteries use a semi-solid electrolyte (sometimes referred to as a “sealed battery”) which do not require maintenance. In a wet cell battery group size, you need to check the water level on and off. Wet cell batteries are basically made for automotive use.

How To Choose the Right Group Size for Battery?

Choosing the right size group for your car batteries is essential to ensuring its lifespan and capacity.

There’s a common misconception among electricians that the group needs to be set at 10 amps per cell. While this may have worked in the past, several things can happen to a battery that won’t occur with higher-amp group size.

Set Your Target Power Output:

Before you start talking about the specifics of a battery, you need to understand the power you’re going to deliver. Most importantly, choose your target power. This means choosing an output level that you can reliably deliver for several hours.

It doesn’t matter if the car will only get 20 miles on a charge with the highest possible performance. If you only plan on driving 20 miles on one charge, your group needs to be large enough that it delivers that level of capacity.

Determine Your Battery Size Requirements:

There are two key elements to any good battery. The first is capacity. Capacity is how many amps you can push through the battery without it being damaged. This will depend on the type of new battery you use. There are a few different types of batteries you’ll find. The most common is lead acid. A lead-acid battery is a common 12V battery and will generally require a 20 amp group size. Before you start researching other characteristics like the cold cranking amp (CCA) rating and terminal position, it’s good to start by consulting a battery size chart.

The second important element is cycle life. This is the amount of time a battery will last between charges. Cycle life is measured in terms of months. A battery that is set to be able to deliver 150 cycles will have the same capacity as a battery that has 200 cycles and 50% more capacity.

So a 20 amp battery that delivers 150 cycles can last twice as long as one that can only deliver 80 cycles. If you know the year, make, model, and engine size of your vehicle, there’s probably a booklet at an auto parts store or an online battery fitment guide you can access with your phone,

Calculate the Ideal Group Size for Your Car Battery:

Once you know what capacity you need and how long your battery will last, you can calculate the ideal size of your group.

For every battery you use, you should expect to have the following:

  • A maximum of 4-8 batteries. The number of batteries will depend on how large your charging system is.
  • An even group size of 10 amps per cell.
  • A minimum of 1-2 batteries. If you use 2 batteries in a 12V system, you need at least 2 because one cell is not equal to 1 amp.
  • A balance of single and dual-cell configurations.
  • This will yield the following ideal sizes.
  • If you have a charger that uses 1 or more batteries, you should be able to use a group size of 5 amps per cell. This will ensure that the output level remains steady.
  • If you have a larger charger, you’ll want a 7.5 amp group size. This will allow for some flexibility when you plan your charging schedule.
  • If you only plan on running one or two batteries, you should be fine with a 10 amp group size. If you have multiple cells, this will also be ideal, but you can always go smaller than this if you want.

Pick the Battery Type You Want:

Once you know what size battery you’re going to need, you can choose the type of battery you want. You can choose to go with lead-acid or lithium-ion. The choice is entirely up to you, but there are some pros and cons to each.

Wrapping It All Up:

It seems like there is a standard group size that works for most people. However, I’m pretty sure that everyone’s needs are different.

I know my needs vary greatly, so it might be worth investigating your own and figuring out what works best for you.

So make sure to read the above guide carefully to know the right group size of your battery.


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Yusuke Kohara
By Yusuke Kohara

Hi, my name is Yusuke Kohara. I'm a research scientist with 20+ years of experience in the battery industry. My knowledge and expertise has been applied to power electric vehicles, mobile electronics, and more! I am also a true car enthusiast. It’s not just about cars for me - it's about all things automotive! I enjoy helping others find their perfect vehicle by providing detailed buying guides as well as reviews on different types of batteries from various manufacturers across the world.



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