Identifying Battery Terminal Type & Group Size

What it is

The Battery Council International (BCI) assigns group numbers to battery case sizes. The group number sets the case dimensions and the terminal layout. Terminal type is a separate choice, though many groups come mostly in one style.

Common terminal types:

• Top post (SAE post): tapered round posts on top. The positive post is larger than the negative, so clamps fit only one way.
• Side terminal: threaded female terminals in the side of the case. Cable ends bolt in.
• Dual terminal: both top posts and side terminals on one battery.
• Stud terminal: threaded studs on top, common on heavy-duty and commercial batteries.
• L-terminal and others: flat tabs with a bolt hole, used on small, marine and specialty batteries.

How to identify

1. Read the label. The group number is usually printed on the top or side label, such as 24F, 31 or 65.
2. Look at the terminals. Note type and which corner holds the positive terminal.
3. Check the suffix. In many groups, an "R" suffix means the terminal positions are reversed from the standard group. Some groups use other letters, such as 24F.
4. Measure the case length, width and height if the label is missing. Compare with the BCI Battery Group Size Chart.
5. Check the hold-down. Some batteries have a ledge at the base for a clamp.

Terminal types

Key points

• Cable length is set for the original terminal position. A reversed layout may not reach.
• Group number does not set CCA or reserve capacity. Match those separately. See Battery Ratings — CCA, CA, RC and BCI Groups.
• Heavy-duty Group 31 batteries come in post and stud versions. Check which the truck uses.
• Protect terminals from shorting during handling.

Common mistakes

• Ordering by group number and missing the R suffix.
• Using a top-post battery where side terminals are needed.
• Forcing an SAE clamp onto the wrong post.
• Ignoring hold-down style.

Governing standards: BCI Battery Replacement Data Book (group sizes and terminal types); SAE J537 (storage batteries).

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.