BCI Battery Size Cross-Reference: Dimensions, H-Series and Fit Guide

BCI Group numbers are most familiar in North America, but they also appear on batteries sold for imported vehicles, motorhomes, boats, leisure systems and replacement applications across Europe. They can be useful for comparing case dimensions, especially when a product is described with both a BCI number and an H, L or LN case designation.

The important point is that a matching case size does not automatically make two batteries interchangeable. The replacement must also have the correct polarity, base hold-down, vent connection, terminal design, battery technology and electrical rating.

BCI Battery Group Size Dimensions Chart

The table below provides common BCI dimensions in millimetres, with inches included for reference. Where widely used, an H-series or European case cross-reference is also shown.

The figures describe common standard envelopes. The exact dimensions of a finished battery may vary slightly, and additional features can affect the installed size.

• Measure in length × width × height order.
• Include terminals, cable lugs and protective covers when checking height.
• Check whether the case uses a B13 base hold-down or another mounting system.
• Confirm the vent-port position on batteries fitted inside a vehicle compartment.
• Use the vehicle or equipment manufacturer’s fitment data for the final selection.

How BCI Sizes Relate to European Battery Codes

Europe uses several overlapping battery references, including EN or ETN product numbers, DIN-derived codes, H-series labels and L or LN case sizes. A BCI number may appear as a cross-reference, particularly on products marketed internationally.

A size cross-reference is useful for comparing the basic case, but it does not guarantee that every detail is the same.

H-Series and LN Case Sizes

• Group 48 / H6 / L3 / LN3: 278 × 175 × 190 mm
• Group 94R / H7 / L4 / LN4: 315 × 175 × 190 mm
• Group 49 / H8 / L5 / LN5: 353 × 175 × 190 mm

These cases have a common width and height, while the length increases. Many vehicles use a bottom ledge for the hold-down, but the approved mounting position, polarity and vent arrangement still need to match.

Why the Full Battery Code Matters

European automotive batteries are frequently identified by more than case size. The product code can also communicate capacity, cold-cranking performance, terminal configuration and other specifications.

For that reason, replacing an H7 battery with any other H7-shaped product is not always appropriate. The battery must support the vehicle’s starting, start-stop and energy-management requirements.

Reversed Terminal Layouts

BCI suffixes such as “R” often identify a reversed terminal arrangement. Group 51 and 51R may share the same basic dimensions while placing the positive terminal on opposite sides.

Polarity should be checked from the same viewing direction used by the manufacturer. Do not rely on a product photograph alone.

Battery Group Size Does Not Define Performance

Case dimensions answer the question “Will it physically fit?” They do not answer “Will it perform correctly?”

After checking the case, compare:

• Cold-cranking current: Match the vehicle manufacturer’s approved EN or other stated rating.
• Capacity in Ah: Important for starting reserve and leisure use.
• Energy in Wh: Helpful for motorhome and off-grid systems.
• Battery technology: Flooded, EFB, AGM and LiFePO4 batteries have different applications.
• Continuous current: Essential for inverters, electric motors and high-load accessories.
• Charging requirements: The vehicle or charger must suit the selected chemistry.

Common Applications in Europe

Passenger Cars and Start-Stop Vehicles

Automotive replacement should begin with a vehicle-specific battery finder or the manufacturer’s approved specification. European vehicles frequently use AGM or EFB batteries to support start-stop systems, regenerative charging and a high number of electrical consumers.

Check:

• Case size and base hold-down
• Positive-terminal position
• EN cold-cranking rating
• Ah capacity
• AGM, EFB or flooded technology
• Vent connection
• Battery coding or registration requirements

Fitting a conventional flooded battery to a vehicle designed for AGM or EFB operation may reduce service life and interfere with the vehicle’s energy-management strategy.

Motorhomes, Campervans and Caravans

A leisure battery has a different job from the starter battery. It may power lighting, a water pump, ventilation, heating controls, refrigeration electronics, USB charging and inverter loads for hours at a time.

An RV and camper battery should therefore be selected by usable energy and output current as well as by case size.

Common BCI-style leisure cases include Group 24, Group 27 and Group 31. GC2 batteries may also appear in multi-battery banks.

A nominal 12.8V 100Ah LiFePO4 battery stores 1,280Wh. The actual operating time available to appliances will be lower after inverter losses, wiring losses, standby consumption and protective cut-offs.

A Group 24-compatible 100Ah lithium battery can be useful in a compact motorhome compartment where a longer Group 27 or Group 31 case will not fit. Confirm the exact dimensions, terminal position, maximum current and low-temperature charging behaviour before installation.

Boats and Marine Electrical Systems

Marine installations may include separate circuits for engine starting, navigation, domestic loads and electric propulsion. The same case size can be used for batteries designed for very different purposes.

• Use a cranking-rated battery for engine starting.
• Compare Ah, Wh and continuous current for domestic loads.
• Match trolling or electric propulsion systems to the correct pack voltage.
• Use secure restraint and insulated positive terminals.
• Confirm whether the battery is approved for the intended mounting position.

Groups 24, 27 and 31 are common international case references in leisure marine systems. Larger 4D and 8D batteries require substantial support and safe lifting access.

Golf Buggies and Utility Vehicles

Golf buggy batteries are selected as a complete pack. Traditional systems may use several GC2 or GC8 batteries connected in series, while a lithium conversion may replace the bank with one integrated unit.

Confirm the total voltage, controller current, charger, cable gauge, fuse, tray dimensions and mounting points. Vatrer lithium golf cart batteries can reduce the number of individual battery cases, but the replacement still needs to match the buggy’s electrical and mechanical requirements.

Solar and Backup Energy Storage

For stationary storage, the Group label is mainly useful for enclosure and floor-space planning. The system should be designed around energy consumption, required backup duration, inverter demand, charge rate and temperature.

Group 31, 4D and 8D cases are familiar in traditional deep-cycle systems. Modern lithium storage may instead use rack-mounted modules or custom enclosures.

Group 24 vs Group 27 vs Group 31

Group 24 vs Group 27

Group 27 retains a similar width and height to Group 24 but adds about 46 mm of length. The change may be possible in a motorhome or boat with unused tray space, but the hold-down and cables must also suit the new case.

Group 27 vs Group 31

Group 31 is only moderately longer than Group 27, but it is approximately 15 mm taller. This can create problems beneath a seat base, metal lid or low shelf once the terminal hardware is installed.

Group 24 vs Group 31

A direct Group 24-to-Group 31 change is normally an installation redesign. It may require a longer tray, larger box, relocated straps, new cables and revised weight support.

When space is fixed, a lithium battery with better usable energy in the original case footprint may be the more practical option.

H6 vs H7 vs H8

The H-series increases mainly in length:

• H6: 278 mm long
• H7: 315 mm long
• H8: 353 mm long

Do not move to the longer case simply because the width and height look correct. Check the vehicle-specific approval, hold-down position, polarity, venting, chemistry and battery-management requirements.

How to Check Battery Fit Correctly

Measure the Usable Base

Measure the flat surface that supports the battery. Account for raised edges, bolts, drains, rounded corners, brackets and cable openings.

The case should sit flat and should not need to be forced into position.

Measure Installed Height

Measure from the battery tray to the lowest obstruction above it. Include the case, terminals, cable lugs, nuts, protective caps and the space needed for cable bends.

Provide safe clearance between the positive connection and any metal cover or seat frame.

Check Terminal and Vent Positions

Confirm the positive and negative terminal locations before purchase. For batteries installed within a passenger or luggage compartment, check the required vent connection and vent-port side.

Confirm the Base Hold-Down

Many European automotive batteries use a bottom mounting ledge, but the ledge position and clamp arrangement must match the vehicle. Motorhome and marine batteries may instead use boxes, straps or top brackets.

The restraint must prevent movement without deforming the case.

Use the Exact Product Drawing

Verify the manufacturer’s stated dimensions, terminal type, polarity, base layout, handle position, weight, approved orientation and intended application.

Replacing Lead-Acid With LiFePO4

A BCI-compatible lithium case may make the physical conversion easier, but it does not make the electrical conversion automatic.

Charging System

Check every charging source, including the mains charger, alternator, DC-to-DC charger, solar controller and generator-powered charger. The voltage and current settings must follow the lithium battery manufacturer’s instructions.

Low-Temperature Protection

Many LiFePO4 batteries should not be charged around or below 0°C unless they include low-temperature charge protection or an approved heating system. This is relevant to motorhomes, boats and unheated outbuildings used during winter.

BMS Output Rating

The battery management system must support the continuous and surge current required by the inverter, motor or connected appliances. A battery can have adequate energy capacity but still be unable to supply a high-power load.

Starter Battery Compatibility

A general-purpose deep-cycle LiFePO4 battery should not be used as an engine starter unless it has a published cranking specification and is approved for the vehicle or engine.

Battery Replacement Checklist

• Identify the complete Group, H, L, LN or ETN reference.
• Measure the tray in millimetres.
• Check the base hold-down and vent connection.
• Include terminal hardware in the height calculation.
• Confirm polarity and cable routing.
• Match the required battery technology.
• Check Ah and cold-cranking performance.
• Verify the charger and battery-management requirements.
• Confirm current ratings for inverters and motors.
• Use the exact vehicle fitment guide and product drawing.

Conclusion

A BCI battery size chart is a useful cross-reference, particularly for imported vehicles and internationally marketed leisure batteries. However, a safe replacement depends on more than matching length, width and height.

Check the full case code, terminal arrangement, base hold-down, venting, battery technology and electrical ratings. For lithium conversions, also confirm charging, BMS output and low-temperature protection. The correct battery is the one that fits securely and meets the complete requirements of the vehicle or energy system.