Battery groups › 51
BCI battery group
Group 51 battery size
A BCI group 51 battery is at most 238 mm long, 129 mm wide and 223 mm tall (9.37 × 5.08 × 8.78 in), according to the Battery Council International group chart.
| Maximum size | 238 × 129 × 223 mm |
|---|---|
| In inches | 9.37 × 5.08 × 8.78 |
| Terminal types | A and A2 |
| Polarity | Standard layout for this group |
| Cold cranking amps (OE range) | 270–500 A |
| JIS equivalents | 46B24R, 55B24R and 65B24R (BCI best fit) |
Cars whose manuals point to group 51
None of the owner's manuals this site has read so far print group 51. Most Japanese and Korean makers print a case size or capacity instead of a BCI group, so the battery label on the car is the better guide.
Measuring for a group 51
To take a group 51, the tray needs at least 238 mm (9.37 in) of length and 129 mm (5.08 in) of width inside the hold-down, and 223 mm (8.78 in) of height below the hood or any bracket, with room left for the cable ends. These are BCI maximums: a real group 51 battery can be a few millimetres smaller, never larger. Original-equipment batteries in this group were rated from 270 to 500 cold cranking amps, so the right rating depends on the car; match or exceed the rating on the battery you are replacing.
Nearby sizes
| Group | L × W × H (mm) | Difference from 51 |
|---|---|---|
| 51R | 238 × 129 × 223 | 0 mm length, 0 mm width, 0 mm height |
| 22NF | 240 × 140 × 227 | +2 mm length, +11 mm width, +4 mm height |
| 45 | 240 × 140 × 227 | +2 mm length, +11 mm width, +4 mm height |
| 62 | 225 × 162 × 225 | -13 mm length, +33 mm width, +2 mm height |
| 56 | 254 × 154 × 212 | +16 mm length, +25 mm width, -11 mm height |
Positive numbers mean the other group is bigger than group 51. A bigger case only fits if your tray and hold-down have that much spare room; measure inside the hold-down frame, not the old battery.
Fitting a group 51
The group sets the case size, terminal position and hold-down. A battery from another group can only replace it when the length, width and height all fit the tray and the terminals land on the same sides. No other passenger-car group in the BCI chart has exactly the same case size and polarity. Use the tray fit checker to list every group that fits a measured space.
Source: Battery Council International, BCI Group Sizes (Oct 2023 PDF), page 6. Checked 2026-10-20.