The BCI battery group size chart is a handy tool to help you select the right battery for your car. With batteries classified by specific BCI groups, it is easy to find the right size and performance for your needs. The Battery Council International (BCI) organization allows different manufacturers to produce batteries with the same specifications. This way, you can be sure that the battery you purchase will fit your car and perform as expected. Here is a guide to the BCI battery group size chart to help you make an informed decision when purchasing a new battery.
What Are Battery Group Sizes?
The concept of “group size” is primarily used in North America and refers to a battery’s physical dimensions. The Battery Council International (BCI) created the group size designation. These dimensions include the battery’s height, length, and width, as well as the polarity of the terminal.
Typically, the group size is stamped on the battery case. The group size designation is important because it ensures that the battery you purchase will physically fit in your car. If you don’t consult a battery size chart, you might purchase a too small or too big battery for your car. That would make it difficult, if not impossible, to install the battery correctly.
In addition to the battery’s physical size, the group size also includes the polarity of the terminal. The positive terminal is either on the left (L) or right (R) side of the battery, as you’re looking at it from the front. It’s important to know the polarity of the terminal because you need to connect the battery to the car’s electrical system. The polarity must match up, or you risk damaging your car’s electrical system.
Common Battery Group Sizes
Comparison Chart
| Battery Group | Dimensions | Weight | |
| Inches | cm | ||
| Group 24 | 10.25 x 6.875 x 8.375 | 26 x 17.5 x 21.3 | 41 – 57 |
| 10.75 x 6.875 x 9 | 27.3 x 17.5 x 22.9 | ||
| 24H | 10.25 x 6.875 x 9.375 | 26 x 17.5 x 23.8 | |
| 24R | 10.25 x 6.875 x 9 | 26 x 17.5 x 22.9 | |
| 24T | 10.25 x 6.875 x 9.75 | 26 x 17.5 x 24.8 | |
| Group 26 & 26R | 8.313 x 6.875 x 7.75 | 21.1 x 17.5 x 19.7 | 28 – 30 |
| Group 27 | 12.063 x 6.875 x 8.375 | 30.7 x 17.5 x 21.3 | 57 – 70 |
| 27F | 12.5 x 6.875 x 8.938 | 31.8 x 17.5 x 22.7 | |
| 27H | 11.75 x 6.875 x 9.25 | 29.8 x 17.5 x 23.5 | |
| Group 31 | 13 x 6.875 x 9.438 | 33 x 17.5 x 24 | 30 – 80 |
| Group 34 & 34R | 10.25 x 6.875 x 7.875 | 26 x 17.5 x 20 | 37 – 51 |
| Group 35 | 9.063 x 6.875 x 8.375 | 23 x 17.5 x 21.3 | 15 – 51 |
| Group 47 | 9.688 x 6.875 x 7.5 | 24.6 x 17.5 x 19.1 | 38 – 42 |
| Group 48 | 12.063x 6.875x 7.563 | 30.7 x 17.5 x 19.2 | 45 – 54 |
| Group 49 | 15.063 x 6.875 x 7.313 | 38.3 x 17.5 x 18.5 | 57 – 63 |
| Group 51 & 51R | 9.375 x 5.063 x 8.688 | 23.8 x 12.9 x 22 | 22 – 45 |
| Group 65 | 12.063 x 7.5 x 7.563 | 30.7 x 19.1 x 19.2 | 45 – 55 |
| Group 75 | 9.063 x 7.063 x 7.75 | 23 x 18 x 19.7 | 34 – 46 |
| Group 78 | 10.25 x 7.063 x 7.75 | 26 x 18 x 19.7 | 38 – 51 |
| Group 86 | 9.063 x 6.875 x 8.125 | 23 x 17.5 x 20.6 | 31 – 46 |
Group 24 Batteries
Group 24 Batteries are mostly available as general-purpose batteries that are ideal for use with medical and security systems, large UPS systems, wheelchairs, vehicles, and some industrial applications. They are typically ideal for deep-cycle float and standby applications.
They are, however, also used as starting and cranking batteries in some applications, but rarely. These batteries are roughly 10.25 long, 6.875 wide, and 8.375 tall. However, these dimensions vary slightly between subgroups, so choosing the right battery for the application is important.
Group 26 and 26R Batteries
Group 26 and 26R batteries are starting batteries used mostly in smaller trucks, SUVs, smaller boats, power generators, and other similar applications. These mid-range batteries have similar dimensions and electric features. The only difference between the two groups is the orientation of their terminals. Group 26 has the positive terminal on the left side, while Group 26R has the positive terminal on the right.
Group 26 batteries are roughly 8.19 inches long, 6.81 inches wide, and 7.75 inches tall. Most of these batteries are lead-acid flooded/wet batteries with a 20-hour capacity of 50 Ah. AGM and gel-cell batteries are also available but less common. A lithium-ion battery is also an option but is not as widely used.
Group 27 Batteries
Group 27 batteries are mostly deep-cycle batteries used in cars, off-the-grid, marine, RVs, and other similar applications. They are typically available as AGM, SLA, and spill-proof batteries, which can be mounted in almost any position. Most of these batteries have 20h capacity in the 66–110 Ah range and can provide 600–1000 CCA (cold cranking amps), 140–220 minutes RC (reserve capacity), and similar electric features.
Group 31 Batteries
Group 31 batteries are large and powerful, mostly used in electric vehicles, off-the-grid applications, marine applications, and other similar uses. Their 20h capacity is 75-125 Ah, providing 750-1250 CCA and 150-250 minutes RC. These size batteries are available in lead-acid, AGM, flooded cell, gel cell, and lithium varieties. Lithium Group 31 batteries are more popular because of their chemistry and electronic advancements. However, they are more expensive.
Even though they are dual-purpose, they don’t have as good starting currents as true starting batteries, but they are better than deep cycle batteries. The deep-cycle group 31 batteries are designed for electric vehicles, off-grid applications, marine applications, and other similar uses that require deep discharge and cycle operations.
Group 34 & 34R Batteries
Group 34 batteries are considered powerful, and their features depend on their intended use. They are commonly used in automotive, marine, and industrial applications. They have a 20-hour capacity of 50-75 Ah, a CCA of 750-900, and a reserve capacity of 100-145 minutes.
Group 34 and group 34R batteries are the same in size and power; the only difference worth noting is the orientation of their terminal posts. While the 34 group has a positive terminal on its left side, the 34R group batteries have their positive terminal on the right, which is why there is the letter “R” after “34”.
Most brands manufacture both the 34 and 34R versions. Therefore, if either is required, purchasing them online would not be a problem.
Group 35 Batteries
Also known as Q85 batteries, Group 35 batteries are very versatile and can be used in many applications. Like group 31 batteries, they are often used as starting or dual-purpose batteries in cars, trucks, SUVs, RVs, and boats. They are also popular in UPS systems, wheelchairs, security system backups, and more.
AGM and gel Group 35 batteries are the most popular lead-acid batteries, but lithium iron phosphate (LiFePO4) batteries are slowly becoming more popular, especially in deep-cycle applications.
The Group 35 batteries are medium-sized, with 20-hour capacities in the 44–65 Ah range and 620–850 cold cranking amps (CCA). They also have a reserve capacity (RC) of 90 to 130 minutes.
Group 47 Batteries
Group 47 batteries are medium-sized batteries. They have applications in the automotive and industrial fields as either cranking or dual-purpose batteries for starting mid-range engines. They are also known as Group H5, L2, and 55L2.
Most Group 47 batteries are spill-proof AGM and hence maintenance-free. However, other cell types are also available. When the battery is facing the user, its positive terminal is on the right side. A good AGM battery from a reputable brand is recommended when looking for a Group 47 battery.
Group 48 Batteries
These batteries typically provide 60-72 Ah of power and have a CCA rating of 720-800 Amps. They also have an MCA rating of 800-930 Amps, an RC value of 120-140 minutes, and weigh between 45 and 54 pounds.
Group 49 Batteries
Group 49 batteries are the preferred car or truck batteries. They are used as both starting/cranking and dual-purpose batteries. They power different loads while the main engine is turned off, similar to various winches and multimedia devices.
BCI Group 49 and Group H8 are considered interchangeable. However, they have several differences, especially in size. When trying to replace the H8 battery with the Group 49 battery, it is essential to note that BCI Group 49 batteries are slightly bigger and therefore require more room in the battery compartment.
Group 51 and 51R Batteries
The batteries are typically dual-purpose or automotive starting batteries. They are mostly used as auxiliary batteries in places requiring consistent and stable power sources. The dimensions are as follows: 9.374 x 5.0625 x 8.8125 inches (23.8 x 12.9 x 22.3 cm).
But the sizes of this group of batteries are not always the same because manufacturers have changed them to fit a wide range of applications.
Group 65 Batteries
Group 65 batteries are mainly dual-purpose automotive batteries, but they are also used for marine and industrial applications. They are usually manufactured with the AGM technology that helps to resist vibrations and spills. However, the lithium-ion types are slowly becoming more common and offer many advantages over other battery types.
Typically, these group batteries provide between 70-75 Ah 20h capacity, 130-150 minutes RC, and 750-950 CCA. Some models can reach up to 1100 amps.
Group 75 Batteries
These are light industry and automotive batteries that are mainly meant for dual-purpose or starting batteries with awesome starting features. These batteries are mainly used in light trucks, cars, and other light vehicles.
They can also provide power for pumps, lights, and winches. The normal size of this category of battery is 230 x 179 x 196 mm. Most batteries in this group have their positive terminal positioned to the left.
With the battery supplying 44 to 60 Ah, you can expect a CCA of 620 to 760 amps and an MCA of 770 to 910 amps. The Group 75 battery is made with AGM technology for increased vibration resistance. When you need a reliable battery that provides a high amount of power, group 75 is an ideal choice.
Group 78 Batteries
Available as starting and dual-purpose AGM batteries, Group 78 batteries are designed to deliver exceptional starting power. They are mostly used in cars and light trucks but can also be used in light industrial and marine and applications.
These batteries provide 50–70 Ah capacity, 700–900 CCA, and 850–1050 MCA. They feature a long life span, up to three times longer than conventional automotive batteries, making them ideal for stop-and-go traffic conditions and other demanding applications.
Many companies sell batteries with the designation “34/78” since the sizes of groups 34 and 78 are very close.
Group 86 Batteries
Group 86 batteries, similar to Group 85 batteries in terms of size and dimensions, are designed for starting/cranking batteries and, as such, are commonly used in automotive and marine applications. The main difference between Group 86 and Group 85 batteries is the orientation of the battery terminals. Group 86 batteries have their terminals oriented in the same direction, while Group 85 batteries are oriented in opposite directions.
Group 86 batteries are mostly lead-acid batteries, with either wet/flooded cells or AGM cells. Most of these batteries supply 45–55 Ah, with a reserve capacity value of 90-95 minutes. The CCA value is usually 500–750 Amps, while the MCA value is usually 650–800 Amps.
Conclusion
As you can see from the above, there is a lot of variation in battery sizes and specifications, even within a single BCI battery group. This is why choosing the right battery for your application is important. If you’re unsure which battery is right for you, work with a qualified battery specialist who can help you select the best option for your needs.
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James is an engineer and a professional blogger. He has gained extensive experience over the years, handling all types of power projects. He loves to share his experiences with all things related to batteries, generators, and other power-related topics.
