Group 51R battery size

Same box, other group numbers

• Group 51: 9.37 x 5.08 x 8.78 in, different terminal layout (BCI figure 10, not 11).

Same box does not mean same battery: if the terminals are on the other side, the cables may not reach.

Before you buy a group 51R battery

• Read the group number on the label of the battery in your car, or in the owner's manual: it should say 51R.
• The "R" means the terminals are reversed compared with the same number without R: the positive post is on the other side.
• Choose cold cranking amps (CCA) at least as high as the original, especially for cold winters.
• Measure your battery tray and the room above it, then compare with the size printed for the exact battery you pick, not only with the group number.
• Group 51R has top posts: the new battery must match, and the hold-down must fit the box.
• Most stores take the old battery back for recycling, often against a core charge.

Good to know about group 51R

• 51R has the same box as group 51 (238 x 129 x 223 mm) but the terminals reversed: BCI draws 51 with layout figure 10 and 51R with figure 11, so do not swap them without checking where the cables reach.^1,2,3
• Retailers' specifications list the positive terminal of a group 51R battery on the right.^4,5
• The Japanese (JIS) size 55B24L is cross-referenced to BCI group 51R.^1,6
• Group 51R is listed for many Honda models and for some Nissan and Mazda models.^3,7
• Group 51R batteries are made in AGM construction.^3,8
• NAPA, Batteries Plus, Interstate and Continental all list a group 51R at about 9 3/8 in (238 mm) long, the BCI figure.^1,4,7,9,10

How we checked this page

Checked on October 16, 2026. We kept a fact only when two independent sources agree, and each one is numbered to its sources below. We never write a price: the listings come straight from eBay and show what sellers ask. This page was written with an AI assistant and checked against the sources below.