Battery Group Size Chart: Complete BCI Battery Dimensions & Cross-Reference Guide

Last updated: October 21, 2026

If you have ever seen labels such as 24F, 27, 31, 35, 48, H6, LN3, 65, or 94R and wondered whether they describe battery capacity, this guide is for you.

The numbers are primarily used to solve a fitment problem: will the battery fit the tray, can it be secured correctly, and will the vehicle's cables reach the correct terminals? But the answer is more nuanced than simply comparing three measurements.

This battery group size chart covers the dimensions people search for most often, explains BCI versus DIN/EN and JIS naming, shows why similar-looking batteries are not automatically interchangeable, and provides a practical replacement checklist you can use before ordering.

What Is a Battery Group Size?

BCI stands for Battery Council International. Its group-size system is widely used in North America to standardize battery fitment across passenger vehicles, trucks, lawn equipment, powersports equipment, farm equipment and other applications.

According to Battery Council International, batteries are classified using characteristics including:

• Maximum overall dimensions
• Terminal position and arrangement
• Performance characteristics
• Battery chemistry and technology designations

That distinction matters because many battery-size explanations online reduce a group number to nothing more than length × width × height.

For a shopper, physical fit is usually the first reason to check the group number, but a battery that fits the tray is not automatically the correct replacement.

Quick Battery Group Size Chart

If you only need the dimensions for the most frequently searched battery groups, start here.

Dimensions above are maximum overall BCI reference dimensions. Always verify the exact battery manufacturer's specification and vehicle fitment before purchase.

Common BCI Battery Dimensions

The following expanded chart covers common passenger-car, light-commercial, RV, marine and utility battery groups without burying the most useful information inside dozens of rare industrial formats.

BCI, H, LN, DIN and EN Battery Size Cross-Reference

European-style batteries are often sold using labels such as H5, H6, H7, H8 or LN2, LN3, LN4, LN5. In the U.S., the same general dimensional families may be advertised under BCI group numbers.

BCI publishes a reference chart connecting these systems, but there is an important limitation: BCI describes these mappings as a best-fit estimate, not a blanket guarantee that every battery carrying one label can replace every battery carrying another.

Is Group 48 the same as H6?

Group 48, H6 and LN3 share the same 278 × 175 × 190 mm dimensional reference in BCI's cross-reference chart. That makes them closely related labels when shopping for replacement batteries.

However, still verify:

• Terminal orientation
• Hold-down design
• CCA requirement
• Flooded, EFB or AGM requirement
• Battery-management or registration requirements

A useful example is BCI Group 148. It shares the 278 × 175 × 190 mm H6/LN3 case family, but BCI identifies a different positive-terminal location. Same-size does not automatically mean same installation.

Is Group 94R the same as H7?

For dimensional cross-reference purposes, Group 94R corresponds to H7/LN4 at 315 × 175 × 190 mm. Again, vehicle approval and terminal configuration must still be confirmed before replacement.

Why H5, H6, H7 and H8 are easy to recognize

These four popular European-style cases share the same nominal width and height in the BCI cross-reference, while length increases:

Moving to the next longer case may look tempting if there is empty space in the tray, but a longer battery should never be treated as an automatic “capacity upgrade.” The hold-down, cables, vehicle specification and electrical system all have to support it.

BCI and JIS Battery Cross-Reference

JIS battery labels are common on Japanese and other Asian-market designs. Their codes look very different from BCI numbers because a JIS designation can include performance class, case width/height family, case length class, and terminal orientation.

The following examples show why a cross-reference is useful.

Group 24 vs Group 27 vs Group 31 Battery Size

Group 24, Group 27 and Group 31 are especially important outside ordinary passenger-car replacement because they frequently appear in RV, marine, commercial, auxiliary and deep-cycle battery discussions.

Group 24 battery size

A standard Group 24 battery has maximum overall dimensions of 260 × 173 × 225 mm, or roughly 10 1/4 × 6 13/16 × 8 7/8 inches.

Do not automatically substitute a 24F, 24R, 24H or 24T just because the label begins with “24.” Their case height, length or terminal arrangement can differ.

Group 27 battery size

A standard Group 27 is 306 × 173 × 225 mm, or approximately 12 1/16 × 6 13/16 × 8 7/8 inches.

Compared with Group 24, it keeps the same maximum width and height but adds 46 mm of length. That additional case length is enough to make a Group 27 unsuitable for a tray designed tightly around Group 24.

Group 31 battery size

What shoppers commonly call a Group 31 battery is approximately 330 × 173 × 240 mm, or 13 × 6 13/16 × 9 7/16 inches.

BCI's reference table distinguishes 31A and 31T. They share the same maximum case dimensions but use different terminal configurations. This is a good example of why “it is a Group 31” is not always enough information to order the correct replacement.

If your Group 24, 27 or 31 battery is part of an RV house system rather than an engine-starting system, see the UDPOWER RV Battery Replacement Guide before changing chemistry or capacity.

Popular Battery Group Sizes Explained

Group 35 battery size

BCI Group 35 measures up to 230 × 175 × 225 mm, or 9 1/16 × 6 15/16 × 8 7/8 inches.

Its footprint is close to Group 25, which is one reason measuring only the outside of an unidentified battery can be misleading. Terminal configuration and the manufacturer's specified group still matter.

Group 48 battery size

Group 48 measures 278 × 175 × 190 mm, or 11 × 6 15/16 × 7 1/2 inches. BCI cross-references it to H6 / LN3.

Do not confuse Group 48 with Group 148. BCI lists Group 148 at the same 278 × 175 × 190 mm dimensions and the same H6/LN3 dimensional family, but with the positive terminal on the opposite side.

Group 65 battery size

Group 65 measures 306 × 192 × 192 mm, or 12 1/16 × 7 9/16 × 7 9/16 inches.

It is noticeably wider than H6 and H7-style cases. A tray with sufficient length therefore may still be too narrow for Group 65.

Group 94R battery size

Group 94R measures 315 × 175 × 190 mm, or 12 7/16 × 6 15/16 × 7 1/2 inches. Its common European cross-reference is H7 / LN4.

It is 37 mm longer than Group 48/H6 while sharing the same nominal width and height in BCI's cross-reference system.

What Do R, F and Other Battery Group Suffixes Mean?

A suffix is not decoration. It can signal an important difference that affects whether the cables, hold-down or battery tray work correctly.

What does “R” mean in a battery group?

In many BCI group families, R identifies a different or reversed terminal arrangement. For example, Group 51 and 51R share the same maximum dimensions, but their terminal layouts differ.

The practical lesson is more important than memorizing the letter:

Always match the full group designation, not just the number.

Does “F” simply mean reversed terminals?

No. Do not treat every suffix as a universal polarity code.

For example, Group 24 and Group 24F are not even identical in maximum dimensions:

That 13 mm difference in length and 4 mm difference in height is another reason not to shop from an abbreviated “Group 24” description when your vehicle specifies 24F.

How to Measure a Battery for Group Size

If the group label is missing or unreadable, physical measurements can help narrow the possibilities. They should not be your only fitment check.

1. Turn the vehicle off and follow the manufacturer's battery safety procedure. Do not place metal measuring tools where they can bridge the terminals.
2. Measure length. Measure the longest side of the battery case.
3. Measure width. Measure across the shorter side of the case.
4. Measure overall height. Include the highest point required by the relevant battery specification, including terminal height where applicable.
5. Record positive and negative terminal positions. Do not rely on case size alone.
6. Identify terminal style. Top post, side terminal, threaded stud and other terminal types are not interchangeable without an approved design.
7. Check the hold-down. Look for bottom ledges, top brackets or other hardware that physically secures the battery.

Measure the available space too

When checking a replacement, battery dimensions are only half of the problem. Also inspect the vehicle's available envelope:

• Tray length and width
• Hood or cover clearance
• Terminal clearance above the battery
• Battery cable length
• Cable bend radius
• Hold-down location
• Vent-tube connection where required

A battery can have a case that clears the tray but still be too tall once cables or terminal covers are installed.

Can You Use a Different Battery Group Size?

Sometimes a manufacturer-approved alternative group exists, but you should not change groups simply because another battery appears to fit.

A safe replacement decision has two separate parts:

1. Mechanical compatibility

• Length
• Width
• Height
• Terminal location
• Terminal type
• Hold-down design
• Vent routing
• Cable reach

2. Electrical and system compatibility

• Correct nominal voltage
• Required cold cranking amps
• Reserve capacity or Ah requirement
• Flooded, EFB, AGM or other required technology
• Charging-system compatibility
• Battery monitoring or registration requirements

This is why a physically smaller battery is not automatically a valid substitute, and a larger battery is not automatically an upgrade.

Is a bigger battery group better?

No. A bigger battery case may provide room for a manufacturer to build a battery with greater energy storage or starting capability, but the group number itself does not guarantee that.

A battery that is “better” on paper can still be wrong for the vehicle if:

• It cannot be clamped securely
• The positive and negative cables do not reach naturally
• The terminal orientation creates a short-circuit risk
• The hood has insufficient clearance
• The chemistry is incompatible with the charging system
• The vehicle requires battery registration or coding

Battery Group Size vs CCA, Ah and Reserve Capacity

One of the easiest mistakes is treating physical battery size as a direct capacity rating.

If you are trying to understand the electrical ratings rather than physical dimensions, read How Many Amps Is a Car Battery?.

If your battery label shows CCA but you need to understand capacity, see CCA to Ah Conversion. There is no exact universal conversion between the two, so Reserve Capacity or an actual Ah specification is more useful when available.

Do Lithium Batteries Use BCI Group Sizes?

They can.

A lithium battery manufacturer may design a LiFePO4 battery around a familiar BCI-size enclosure so it can physically fit an existing battery tray or compartment. That does not mean a lithium battery is automatically a drop-in electrical replacement for a flooded lead-acid or AGM battery.

Before changing chemistry, check:

• Charging voltage requirements
• Alternator compatibility
• Low-temperature charging protection
• Battery-management-system limits
• Maximum continuous and peak current
• Vehicle or equipment manufacturer approval
• Physical hold-down and terminal design

This matters especially in RV house-battery systems, solar systems and deep-cycle applications. For a detailed chemistry comparison, see Deep Cycle Batteries Explained.

If you are sizing a battery for solar or off-grid runtime rather than replacing a vehicle starter battery, the 12V Solar Battery: 50Ah vs 100Ah vs 200Ah Guide explains capacity and runtime in more useful terms.

7-Point Battery Replacement Checklist

Use this sequence instead of starting with “Which battery is biggest?”

The fastest way to identify the correct group

Use this order:

1. Check the owner's manual or manufacturer fitment information.
2. Read the full group designation on the existing correctly fitted battery.
3. Use BCI dimensions as a verification step.
4. Check the exact replacement battery specification sheet.
5. Confirm the electrical rating and chemistry before purchase.

BCI maintains replacement data covering a large range of vehicle and equipment applications. You can learn more through its Vehicle Battery Replacement Data resource.

When a Portable Power Station Makes More Sense Than a Larger Vehicle Battery

A larger battery group is not always the right answer when your real goal is to run laptops, lights, a CPAP machine, a portable refrigerator, cameras, chargers or other accessories.

A vehicle starter battery is designed around the vehicle's electrical system. Repeatedly draining it to run accessories can leave you without enough starting power.

For independent accessory power, camping or emergency backup, a portable power station separates those loads from the vehicle's installed starter battery.

UDPOWER C400: Portable Power Plus 12V Jump-Start Support

The UDPOWER C400 Portable Power Station is not a replacement for a BCI automotive battery. Instead, it provides a separate portable energy source for road trips, camping and emergency use.

• Battery capacity: 256Wh LiFePO4
• Rated AC output: 400W pure sine wave
• Peak output: up to 800W
• Vehicle feature: EC5 jump-starter port
• Jump-start rating: product specifications list up to 400A peak for compatible 12V vehicle starting
• Other outputs: AC, USB-C, USB-A, DC5521 and 12V car output

Keep the jobs separate:

Your BCI group size determines the correct installed vehicle battery. A portable power station provides independent portable power and should not be treated as a substitute for the vehicle's required starter battery.

View UDPOWER C400 View All Portable Power Stations

For larger RV and camping loads, see UDPOWER Portable Power Stations for RV & Camping. If you are not sure how much portable capacity you need, use the UDPOWER Power Station Comparison to compare capacity, rated output and intended use.

Frequently Asked Questions

Bottom Line

A battery group size chart is most useful when you treat it as a fitment reference rather than a shopping shortcut.

Start with the vehicle-approved group number. Then confirm the physical dimensions, terminal orientation, hold-down, electrical rating and battery technology. If you see another naming system such as H6, H7, LN3 or LN4, use the BCI cross-reference to understand the relationship—but do not skip the final fitment check.

For the most frequently searched groups, remember these reference sizes:

• Group 24: 260 × 173 × 225 mm
• Group 27: 306 × 173 × 225 mm
• Group 31A/31T: 330 × 173 × 240 mm
• Group 35: 230 × 175 × 225 mm
• Group 48 / H6 / LN3: 278 × 175 × 190 mm
• Group 65: 306 × 192 × 192 mm
• Group 94R / H7 / LN4: 315 × 175 × 190 mm