When purchasing a battery, you will see a series of numbers and letters in the name. These numbers and letters are the BCI group size of the battery. BCI stands for Battery Council International. This is a trade association that. First, each vehicle comes with a specific battery tray size, whether it's a car, truck, SUV, commercial vehicle, boat, recreational vehicle, or other vehicles. It is important to choose a. When choosing a battery, it is important to use the ones that are recommended by the manufacturer for your make and model of the vehicle. The easiest way to find out what battery group you need is to measure your old battery or your. BCI is the most common system used to classify battery group sizes. The following battery group size chart explains the most common BCI battery. The BCI designationsinclude the group definition, dimensions, measurements, types, sizes, and other characteristics. The battery conversions chart can help you to cross-reference battery.