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JIS Battery Size Codes Explained

How to decode JIS D 5301 battery codes such as 55B24L, 95D31R and 245H52: performance rank, case group, length, terminal position, the (S) suffix and idling-stop codes.

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Most batteries fitted to Japanese-built cars, pickups and trucks are identified by a code defined in JIS D 5301, the Japanese Industrial Standard for 12 V lead-acid starter batteries. The current edition is JIS D 5301:2019, which replaced the 2006 edition and was prepared with reference to IEC 60095-1, IEC 60095-2 and IEC 60095-4. A JIS code is compact, but each character carries specific information. This guide decodes the code in detail and explains the parts that are most often misread on purchase orders. For a broader comparison of JIS, N-series, DIN/EN and BCI codes, see how automotive battery sizes work.

The four parts of a JIS code

Code Performance rank Case group (width × box height) Length (approx. cm) Terminal position
55B24L 55 B 24 L
80D26L 80 D 26 L
95D31R 95 D 31 R
115D31L 115 D 31 L
145F51 145 F 51 No letter
245H52 245 H 52 No letter

1. Performance rank

The leading number is a performance rank, not a capacity. JIS D 5301:2019 calculates it from the rated cold cranking current (Icc, in A) and the rated reserve capacity (RC, in minutes):

Performance rank = √(Icc × RC) ÷ 2.8

The result is shown in steps of 2 below 50 and in steps of 5 from 50 upwards, which is why codes read 38, 40, 44, 46, 50, 55, 60 and so on. The Battery Association of Japan (BAJ) gives the worked example of a battery rated at 370 A and 64 minutes: √(370 × 64) ÷ 2.8 = 55.0, displayed as 55.

Two consequences matter for buyers:

  • A higher rank in the same case is a stronger battery, so 80D26L outperforms 65D26L while fitting the same space.
  • The rank does not equal Ah. In the standard's own type table, 55B24L has a 20-hour capacity of 42 Ah and 80D26L has 63 Ah. Capacity must be read from the specification, not inferred from the code.

2. Case group letter

The letter defines the width and box height of the case. Box height excludes the terminals. BAJ publishes the following values, which match the case table in JIS D 5301:2019 (the standard itself covers B to H):

Letter Width (mm) Box height (mm) Maximum total height in JIS D 5301 (mm)
A 127 162 Not listed
B 129 (127 for B17 and B19) 203 227
D 173 204 225
E 176 213 234
F 182 213 257
G 222 213 257
H 278 220 270

These are maximum case dimensions with negative tolerances, so manufacturers' published dimensions are usually a few millimetres smaller. GS Yuasa's technical data, for example, lists its D-case batteries at 171 mm wide with a 222 mm total height. Always confirm total height against hood clearance.

3. Length

The number after the letter is the approximate case length in centimetres. It is a rounded value: in JIS D 5301:2019 the maximum length of a B24 case is 238 mm, a D26 case 260 mm, a D31 case 306 mm and an H52 case 521 mm.

4. Terminal position: L and R

For B to E cases, JIS D 5301 recognises two mirror-image terminal arrangements, marked L and R. GS Yuasa defines them as follows: looking at the battery from the short side nearest the positive terminal, if the positive terminal is on the left it is an L type; if it is on the right it is an R type.

Put another way, with the battery on a bench and the terminals along the long side nearest you, an L type has its positive terminal at the right-hand end. That is the same arrangement as European layout 0, and catalogues that list both systems pair them that way: Varta's catalogue gives D31L as layout 0 and D31R as layout 1, and GS Yuasa lists R and L types as layouts 1 and 0.

The large F, G and H cases carry their terminals differently, and codes for these sizes have no letter in the standard arrangement. Catalogues show the reversed arrangement with an L, for example 115F51 and 115F51L.

JIS D 5301:2019 also notes that types ending in R are designated for future discontinuation. R-type batteries are still listed by manufacturers and remain in the vehicle population, so replacement demand continues.

Terminal layouts across standards are compared in the battery terminal layout guide.

The (S) suffix: which terminal post?

JIS D 5301 defines two tapered terminal sizes: a thin terminal, T1 (positive 14.7 mm, negative 13.0 mm diameter), and a thick terminal, T2 (positive 19.5 mm, negative 17.9 mm), which has the same diameters as the standard European post. B-group cases may be built with either. For those types, the standard adds "(S)" to the end of the code when the thick T2 terminal is used.

This is frequently described the other way round, as "S for small terminal". The standard does not support that reading, and neither does manufacturer data: GS Yuasa's technical data lists 46B24L and 46B24L(S) with different terminal codes, the (S) version sharing the terminal code of its D-case batteries.

In practice:

  • B19, B20 and B24 batteries without the suffix commonly have thin posts.
  • The (S) version of the same code has the thicker standard post.
  • The two are not interchangeable without changing or adapting the cable clamps.

When an order line reads "46B24LS", confirm whether the customer means the (S) variant as defined in JIS, or has used "S" informally to mean small posts. A photograph of the existing terminals removes the doubt.

Codes that look like JIS but are not

Idling-stop codes (SBA S 0101)

Batteries for Japanese idling-stop vehicles follow a separate BAJ standard, SBA S 0101, with codes such as M-42, N-55, Q-85 and S-95. The letter is the case size, the number is the performance rank, and a trailing R marks the reversed terminal position (no letter means an L type). GS Yuasa publishes the case correspondence:

Conventional case Idling-stop letter Conventional case Idling-stop letter
B17 J D26 S
B19 K D31 T
B20 M E41 U
B24 N F51 V
D20 P G51 W
D23 Q H52 X

A conventional battery with the same case is not a substitute on an idling-stop vehicle. See start-stop batteries and EFB vs standard flooded batteries.

S prefix: valve-regulated batteries

A code that starts with S, such as S55B24R, identifies a valve-regulated (VRLA) battery. GS Yuasa notes that these are widely used as auxiliary batteries in Toyota hybrid vehicles, often installed in the cabin or luggage area, and cannot be replaced with a conventional vented battery. See the EV and hybrid 12 V auxiliary battery guide.

EN sizes on Japanese vehicles

Some recent Japanese vehicles use European LN-size batteries. BAJ standardises these for the Japanese market in SBA S 0102. They follow EN dimensions and terminal conventions, not JIS codes; see the DIN/EN battery sizes guide.

Worked examples from the standard

The ratings below are the values listed for these types in JIS D 5301:2019, with the maximum case dimensions for their size groups. Individual manufacturers may rate their batteries above these values, so treat them as reference points rather than product specifications.

Code Rated CCA (A) Rated RC (min) 20 h capacity (Ah) Max. case length × width × box height (mm)
55B24L 370 64 42 238 × 129 × 203
80D26L 490 103 63 260 × 173 × 204
95D31L 565 125 74 306 × 173 × 204
115D31L 710 145 81 306 × 173 × 204
245H52 1,170 405 205 521 × 278 × 220

95D31L and 115D31L share a case but differ substantially in cranking current, which is exactly what the rank communicates. Codes that do not appear in the standard's type list, which some manufacturers use for intermediate ratings, still follow the same structure, but their ratings can only come from the manufacturer's data sheet.

What to put on an order line

  1. The full code, including the terminal letter and any (S) suffix.
  2. Terminal post type if there is any doubt, ideally with a photo.
  3. Technology: conventional, maintenance-free, EFB or AGM.
  4. Minimum 20-hour capacity and cold cranking current, with the test standard. See how to select a battery by Ah and CCA.
  5. Supply condition: filled and charged, or dry-charged.

Browse JIS batteries or send a list through the battery requirement form.

References

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