We are all familiar with the fact that batteries come in various shapes and sizes, but what exactly is meant by the term "group" for battery? The simple answer, in the context of car batteries, is that group refers to size. If such a system were also used in the footwear industry, you might walk into Footlocker and request a pair of Group 11 Vans Old Skool sneakers.
So why do battery experts utilize the term "groups" rather than "sizes"? Possibly because, like many industries, they enjoy using technical jargon that can render the topic confusing. For example, a Group 34 battery might actually be smaller than a Group 27 battery while still being larger than a Group 51 battery--seeming a bit counterintuitive, but it's the reality!
There are various organizations responsible for classifications of batteries, such as BCI (Battery Council International) ,DIN and EN. BCI lists common sizes such as Group 34, Group 27, Group 31, and Group 35. Meanwhile, DIN, which stands for Deutsches Institut für Normung or German Institute for Standardization, also offers its classification for batteries such as H6, H7, and H8. EN is short for European Norm. The European Norm is an agreement between the countries in Europe to consolidate the specification of standards to enhance the efficiency of commerce.
Does this imply that every German vehicle employs DIN sizes while American vehicles rely on BCI sizes? Unfortunately, the answer is not so straightforward due to the confusing nature of the battery industry. A 2016 Mini Cooper, for instance, uses an H6 as its DIN group (battery size), whereas the BCI regards the identical battery as a "Group 48" option.
Thankfully, there exists a correlation between the BCI and DIN battery sizes. A convenient cross-reference chart is available that outlines the most commonly used BCI battery groups alongside their corresponding DIN and EN equivalent codes.
| Maximum DIN/EN Battery Dimensions (L*W*H mm) | DIN Code Size | EN Code Size | Maximum BCI Battery dimensions (L*W*H, mm or inch) | BCI Group Size |
| 175*175*190 | H3, L0 | 32L0 | - | - |
| 207*175*175 | T4, LB1 | 36LB | 207*175*175 (8 1/8*6 7/8*6 7/8) | G99 |
| 210*175*175 | T4, LB1 | 36LB | 210*175*175 (8 1/4*6 7/8*6 7/8) | G99R |
| 207*175*190 | H4, L1 | 45L1 | - | - |
| 242*175*175 | T5, LB2 | 45LB | 246*175*175 (9 11/16*6 7/8*6 7/8) | G90 |
| 242*175*175 | T5, LB2 | 45LB | 237*173*173 (9 5/16*6 13/16*6 13/16) | G42 |
| 242*175*190 | H5, L2 | 55L2 | 242*175*190 (9 7/16*6 7/8*7 1/2) | G47 |
| 252*175*190 | H5, L2 | 55L2 | 252*175*190 (9 15/16*6 7/8*7 1/2) | G97R |
| 278*175*175 | T6, LB3 | 66LB | 280*175*175 (11*6 7/8*6 7/8) | G91 |
| 278*175*175 | T6, LB3 | 66LB | 277*175*175 (10 15/16*6 7/8*6 7/8) | G40R |
| 278*175*190 | H6, L3 | 66L3 | 278*175*190 (11*6 7/8*7 1/2) | G48 |
| 283*175*190 | H6, L3 | 66L3 | 283*175*190 (11 1/8*6 7/8*7 1/2) | G98R |
| 293*175*175 | T65 | 54LB | 293*175*175 (11 3/16*6 7/8*6 7/8) | G41 |
| 315*175*175 | T7, LB4 | 77LB | 317*175*175 (12 1/2*6 7/8*6 7/8) | G92 |
| 315*175*190 | H7, L4 | 77L4 | 315*175*190 (12 7/16*6 7/8*7 1/2) | G94R |
| 354*175*175 | T8, LB5 | 88LB | 354*175*175 (15*6 7/8*6 7/8) | G93 |
| 354*175*190 | H8, L5 | 88L5 | 354*175*190 (13 15/16*6 7/8*7 1/2) | G49 |
| 394*175*190 | H9, L6 | - | 394*175*190 (15 9/16*6 7/8*7 1/2) | G95R |
BCI battery groups, DIN, and EN codes cross reference chart
Note: This cross-reference chart only lists the dimensions of the battery and does not include information about the orientation of its terminals, terminal types, base hold-down type, lifting edge, and other seemingly minor, yet often crucial details.
Conclusion
Battery sizes may appear similar, differing only marginally in size. However, before considering an interchangeable battery, ensure that the new battery satisfies the following requirements: it fits snugly into the battery compartment, its terminals are correctly oriented, its specifications and features are of the same or better quality than the old battery, and it can be charged properly. Despite these precautions, it is always recommended to consult with professionals before replacing a battery with a different goup size. Failure to do so may result in damage, injuries, or worse consequences.
