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Battery Sizes Explained: Choosing the Right Size For Your System And Use

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It’s no secret that the batteries you put in your TV remote are not the same as the battery under the hood of your car. Your application typically determines the battery size you need, and in some cases, you may have multiple choices that will work. Today we’re going to dig deeper into the different battery sizes available and how to choose the best one for your system.

Standardization of Battery Sizes

The importance of the standardization of battery sizes is probably not something you think about every day and is likely something we all take for granted. If the AA batteries in your flashlight die, you expect that if you buy replacements, they will fit and work just like the dead ones. Without battery size standardization, this would not be the case.

Batteries in various sizes

The International Electrotechnical Commission (IEC) publishes international standards for all electrical and electronic-related technologies, including batteries. Non-rechargeable batteries fall under the IEC standard 60086, and rechargeable batteries, such as automotive batteries, are standardized according to IEC 60095. 

Battery Sizes for Household Electronics

The most common battery sizes for small household electronics are AA and AAA. Both of these batteries are cylindrical batteries with a nominal voltage of 1.5 volts. AAA batteries are physically smaller than AA batteries and also typically have about half of the capacity. Remote controls, small flashlights, and similar small electronics requiring minimal power often use AA and AAA batteries.

For larger household electronics, the most common battery size options are C and D. D-size batteries are larger than C-size and have about 50% more capacity as a result. C and D-size batteries are often used in higher power applications such as portable stereos or industrial electronics that need to run for a long time. 

The other common household battery size is the E-size battery, more commonly referred to as a 9-volt battery. 9-volt batteries are rectangular and are the most common batteries found in smoke detectors.

Battery Cell Shapes: Cylindrical, button, and prismatic

There are three common battery cell shapes to consider: Button cells, prismatic cells, and cylindrical cells. The different cell shapes come in different sizes and chemistries and are optimized for various applications. Typically, battery cells are connected in series or parallel to make larger batteries. For example, it’s common to construct deep-cycle lithium batteries out of many individual cylindrical lithium battery cells.

cylindrical cells inside a lithium battery

Button cells are small round batteries that look like a button and are common in very small electronics that require minimal power. For example, watches, key fobs for a car, hearing aids, and medical devices all use button cell batteries.

Prismatic cells are thin, rectangular battery cells that are becoming obsolete. They are expensive to manufacture and do not have good thermal management, which tends to cause them to have a shorter lifecycle than cylindrical cells. Low-profile devices like phones, tablets, and laptops often use prismatic cells.

Cylindrical cells are the most common cell type. The common household batteries mentioned earlier (AA, AAA, C, and D) are cylindrical cell batteries. Cylindrical cells are the most robust cell type, and when combined in a battery pack, they offer a higher energy density than prismatic cells.

→ Learn more here at Lithium Battery Basics: What’s Inside A Lithium-Ion Battery?

What Are Battery Group Sizes?

In North America, the Battery Council International (BCI) publishes standard group sizes for rechargeable batteries like those found in cars, boats, and RVs. The group size determines the physical dimension constraints of the battery, not the capacity. Typically, a larger battery size results in a higher capacity. However, this is not always true.

There are over 50 different battery group sizes. The chart below shows some of the most common ones. As you can see, the group sizes are designated by a number. 

battery group size chart

A common mistake is to think that the larger the group number is, the bigger the battery will be. This is not always the case, either. For example, a group 31 battery is larger than a group 51 battery.

Battery Sizes for Cars, RVs, Boats, and Golf Carts

There is no single group size that all cars, RVs, boats, or golf carts use. Vehicle manufacturers will recommend or specify a group size based on the needs of that particular vehicle.

However, the most common group sizes for passenger vehicles are 24, 27, 34, 35, 48, 49, 65, and 78. Many RVs and boats will use similar group sizes as passenger vehicles. However, it is common for large RVs, boats, and trucks to use an 8D group size battery. 8D batteries are larger and have a much higher capacity.

multiple lithium battery sizes lined up on boat

Golf carts have their own battery size groups, which are preceded by the designator “GC.” The most common battery size for golf carts is the GC2 which is a 6-volt battery. The other common options are the GC8 (8 volts) and GC12 (12 volts).

→ Find out Everything You Need To Know About Golf Cart Batteries

Chemistry, Voltages, Amps, & Amp-Hours


There are four main battery chemistries that the majority of batteries fall within: Lead-acid, Nickel-Cadmium (Ni-Cd), Nickel-metal Hydride, and Lithium-ion. Within these four main chemistries, there are multiple sub-chemistries. For example, there are many different types of lithium batteries with varying applications ideal for each.

The key difference in the four main chemistries is energy density. The graph below shows that lithium batteries have the highest energy density, followed by Ni-MH, Ni-Cd, and finally, lead-acid. A higher energy density means that more energy can be stored in a smaller and lighter battery. 

Battle Born Batteries specific energy density vs volumetric energy density graph

Energy density is not the only factor in choosing the best battery chemistry for your application. The different chemistries have trade-offs as well. For example, lead-acid batteries make better starting batteries than lithium batteries because they can provide extremely high cold-cranking amps (short burst of high current to start your car), whereas lithium batteries cannot.


Not only do batteries come in different physical sizes, but they also have varying voltages. Battery voltages can range from 1.5 volts in AA and AAA batteries to 36 volts for some deep-cycle batteries. 

A good rule of thumb is that the higher the power requirement is for an application, the larger the battery voltage tends to be. The reason for this is that power is equal to the product of voltage and current ( voltage (volts) X current (amps) = power (watts) ). In high power applications, having a higher voltage reduces the current, allowing smaller cabling to be used.

Amps & Amp-Hours

The final and possibly most important factor in battery sizing is the capacity of the battery. We measure battery capacity in amp-hours (Ah), which is the product of multiplying amps by hours. 

→ Suggested Reading: What Are Amps and Amp-Hours?

For example, a battery with a 100 Ah capacity can deliver approximately one amp for 100 hours, or two amps for 50 hours, or four amps for 25 hours, and so on. The capacity rating is an approximation and is not exact.

Battle Born Batteries Sizes Explained

Here at Battle Born Batteries, we offer various battery sizes of lithium deep-cycle batteries in varying form factors, voltages, and capacities. 

12V and 24V Batteries

The most common voltage for deep-cycle batteries is 12 volts. Most of the batteries that Battle Born offers are 12-volts; however, we also offer a 24-volt, 50 Ah option

100Ah Lithium Batteries

Deep Cycle Replacement

The most commonly purchased Battle Born battery is the 100 Ah deep cycle drop-in replacement. The 100 Ah battery is a drop-in replacement for group 27 and group 31 lead-acid batteries.

100 ah 12v lifepo4 Battle Born Battery


We also offer our 100 Ah battery in a GC2 form factor for golf cart applications. GC2 form factor batteries are typically 6 volts. However, most golf carts run on 24 or 48 volts, so you often need to wire up to eight 6-volt batteries in series. Since our GC2 battery is 12 volts, you need half as many batteries in your golf cart, saving you weight and space. 

gc2 lithium Battle Born Battery

270Ah Lithium Batteries

We offer two form factors of 270 Ah capacity lithium batteries for applications requiring a lot of power.

8D Battery

The first option is a 270 Ah, 12-volt 8D drop-in replacement. This lithium battery is about 50 pounds lighter than a standard lead-acid 8D battery and packs almost double the capacity.

12V 270Ah LiFePO4 Deep Cycle 8D Battery
12V 270Ah LiFePO4 Deep Cycle 8D Battery

GC3 Battery

We’re changing the game with this 12V LiFePO4 deep cycle battery. The BBGC3 is a 270Ah 12V LiFePO4 deep cycle battery in a unique battery case and shape that changes the way batteries can be placed inside RVs.

Rather than adhering to a traditional battery size that needs to fit in a battery box to allow for ventilation from off-gassing, we have created a battery that can be placed anywhere.

BBGC3 12v LiFePO4 deep cycle battery side view
A front-facing view of the BBGC3 12v LiFePO4 deep cycle battery

50Ah Lithium Batteries

Lastly, we offer two 50 Ah batteries. The first is a 24-volt, 50 Ah battery that is a drop-in replacement for group 27 and 31 batteries. While it only has a 50Ah capacity, the watt-hour capacity is the same as our 100 Ah, 12-volt batteries. 

Additionally, for smaller applications that don’t require a ton of power, we have a 50 Ah, 12-volt lithium battery available. The great thing about this battery is that it weighs less than 18 pounds, so you can take it just about anywhere!

12v 50ah lithium battery size

Choosing the Right Size for Your System

Choosing the right battery size for your system and application is about more than just getting the biggest battery you can find and afford. There are many different form factors, voltages, and capacities available. 

Before jumping in and buy a new battery, determine what your power needs are, how much space you have available, and your budget. Whatever your combination of needs is, there is likely a perfect battery size for you. If you need help determining your best options, please reach out to our team of experts here at Battle Born. We’re always happy to help!

Want To Learn More About Electrical Systems and Lithium Batteries?

We know that building or upgrading an electrical system can be overwhelming, so we’re here to help. Our Reno, Nevada-based sales and customer service team is standing by at (855) 292-2831 to take your questions!

Also, join us on Facebook, Instagram, and YouTube to learn more about how lithium battery systems can power your lifestyle, see how others have built their systems, and gain the confidence to get out there and stay out there.

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