What the digits encode
BCI (Battery Council International) group sizes are a North American standard. The number identifies a specific case size (length × width × height) and terminal layout. Group 65 batteries are always 305 × 190 × 192 mm with top-post terminals; Group 47/H5 batteries are always 242 × 175 × 175 mm with European-style flush-recessed terminals. The number doesn't tell you CCA — you can have a low-CCA Group 65 and a high-CCA Group 65 sharing the same case.
Suffixes: R, /H5, /H6, C, F
- R = Reversed terminals (positive on the right when you face the battery). 51 vs 51R, 96R vs 96.
- /H5, /H6, /H7, /H8 = European DIN dimensions cross-listed against BCI for North American compatibility. 47/H5 is interchangeable with a European H5 battery.
- C = Commercial — typically a slightly deeper case for higher capacity in the same footprint.
- F = Side-terminal (terminals on the long side rather than the top). Common on older GM vehicles.
How to look up your group
Three ways: read the top of the existing battery (the group is usually stamped or printed in white), check the owner's manual (under battery or electrical), or use our fitment finder by year-make-model. The first two are the most reliable when the dealer-installed battery isn't the OEM size — it happens.
If you can't read the existing battery and don't have the manual, take a photo of the battery from above and call us — terminal layout, vent shape, and case proportions are usually enough to identify the group.