Battery Terminal Layout Guide

Two batteries with identical dimensions and ratings can still be different products because their terminals are arranged as mirror images or their posts are different sizes. Terminal layout errors are among the most common reasons a correctly sized battery is rejected at installation. This guide sets out how the main standards describe terminal position and post type, how the systems correspond, and what to confirm before quoting.

Why layout matters

Vehicle battery cables are cut to length and routed for one terminal arrangement. When the layout is reversed:

• The cables may not reach, or can only be connected under strain.
• The positive cable can end up near the negative post, which invites a reverse-polarity connection.
• Terminal covers, fusible links and battery sensors mounted on the cable may not fit the other way round.

ZVEI, the German electrical industry association, lists a different terminal layout as a cause of damage to the vehicle's electrical system in its guidance on battery selection. It also points out that positive and negative posts are made with different diameters specifically to prevent the cables being swapped. Varta's replacement guidance similarly advises noting the arrangement of the positive and negative terminals before removing the old battery, to prevent reverse polarity.

Polarity marking

IEC 60095-2:2021 requires starter batteries to carry a polarity marking, at least on the positive terminal: a "+" symbol on the top of the terminal or on the lid next to it, and a "−" symbol for the negative terminal. The words "POS" and "NEG" are permitted as an alternative for the North American market only. Always read the marking on the battery itself rather than relying on the colour of a terminal cover.

JIS terminal position: L and R

JIS D 5301 cases in groups B to E exist in two mirror-image arrangements, identified by the last letter of the code (for example 80D26L and 80D26R).

GS Yuasa defines the letters this way: viewed from the short side of the battery nearest the positive terminal, an L type has the positive terminal on the left and an R type has it on the right. Seen from above with the terminals along the long side nearest you, this means:

The large F, G and H cases have their terminals at one end of the battery. Their standard arrangement carries no letter, and catalogues identify the reversed arrangement with an L, for example 145G51 and 145G51L.

The code system is explained in full in JIS battery size codes explained.

European terminal layouts: 0, 1, 3 and 4

European catalogues give the layout as a number. ZVEI's drawings show the battery from above with the terminals on the near side:

Some catalogues also draw further layout numbers for less common arrangements. Where a number other than 0, 1, 3 or 4 appears, check the manufacturer's drawing. European sizes are covered in the DIN/EN battery sizes guide.

How JIS and European layouts correspond

For long-side terminal batteries the two systems describe the same two arrangements:

Manufacturers that publish both systems pair them this way. Varta's technical specifications list D31L as layout 0 and D31R as layout 1, and GS Yuasa's technical data gives R and L types as layouts 1 and 0.

The letters are easy to misread because "L" does not mean "positive on the left" in the usual bench view. When a customer describes a battery in words ("positive on the left"), ask which side they were looking from, or ask for a photograph.

BCI group numbers

North American BCI group sizes also have standard and reversed versions, often distinguished by an R in the group number (for example 99 and 99R). The BCI reference chart records the positive terminal location for each group in its own drawing convention. Do not assume that an R in a BCI group and an R in a JIS code describe the same arrangement; compare the drawings.

Terminal post sizes

Layout describes where the terminals are; post type describes what the cable clamps attach to. The main tapered posts are:

Points to note:

• The JIS (S) suffix marks the thick post, not a small one. JIS D 5301:2019 adds "(S)" to types available with either post when the thick T2 post is used. A 46B24L normally has thin posts; a 46B24L(S) has thick posts.
• Thin and thick posts are not interchangeable without replacing or adapting the clamps.
• BCI lists SAE, DIN, EN/JIS and JIS pencil posts as separate post types. Confirm clamp compatibility rather than assuming an SAE clamp fits a European or JIS post.
• Other terminal types exist: side terminals, threaded studs, marine dual terminals and bolt-on terminals on some commercial and deep cycle batteries.

Checklist before quoting

Browse JIS batteries, DIN and EN batteries or truck and bus batteries, use the battery vehicle finder as a starting point, and send confirmed specifications through the battery requirement form.