The group size of a car battery is a standardized code, established by the Battery Council International (BCI), that defines its physical dimensions, terminal locations, and type. It ensures a new battery will physically fit and properly connect in your specific vehicle. The correct group size is non-negotiable for a secure installation.
To find the right group size for your car, the most reliable methods are to check your owner's manual or look at the label on your current battery. It will be a code like Group 35, Group 48, or Group 65. Using the wrong size can lead to improper fitment, potential damage from vibration, and even electrical shorts if the terminals contact the hood or a bracket.
The group size system is essential because it allows for a wide variety of battery types—from standard flooded lead-acid to more advanced Absorbent Glass Mat (AGM) batteries—to be designed to fit specific vehicle platforms. While two batteries can share the same group size, their performance specs, like Cold Cranking Amps (CCA) and Reserve Capacity (RC), can differ significantly. CCA measures the battery's ability to start an engine in cold weather, while RC indicates how long it can run essential accessories if the alternator fails.
Here is a comparison of some common BCI group sizes found in vehicles in the U.S. market:
| BCI Group Size | Common Vehicle Applications (Examples) | Physical Dimensions (L x W x H in inches) | Terminal Type |
|---|
| Group 35 | Honda Civic, Toyota Camry, Subaru Outback | 9.06 x 6.88 x 8.88 | Top Post |
| Group 48 (H6) | Many European sedans, BMW 3-Series, Audi A4 | 10.94 x 6.88 x 7.68 | Top Post |
| Group 49 (H8) | Large SUVs/Trucks, Ford F-150, Jeep Grand Cherokee | 13.03 x 6.85 x 8.35 | Top Post |
| Group 65 | GM trucks/SUVs, Chevrolet Silverado, Cadillac Escalade | 12.06 x 7.56 x 7.69 | Top Post |
| Group 24F | Older Japanese models, some Toyota trucks | 10.25 x 6.78 x 9.25 | Top Post (Reverse Polarity) |
| Group 94R | Chrysler, Dodge, Jeep models | 12.44 x 6.88 x 7.56 | Top Post |
When replacing a battery, always prioritize the correct group size first, then select the highest CCA and RC ratings that fit your budget for the most reliable performance.
