Group 51 and 51R Batteries - Dimensions, Features and Recommendations (2024)

BCI Groups 51 and 51R batteries are very popular automotive starting and dual-purpose batteries, and are often being used as general-purpose/auxiliary batteries in various applications requiring stable and reliable power sources.

Although Groups 51 and 51R batteries have their size defined, their size tends to vary a little bit - some manufacturers optimized their batteries for certain applications, and make them slightly smaller (easier fit) or even larger (better performances). So, before ordering a certain model, check the actual size of the battery and the size of your battery compartment.

Updated: May 14, 2021.

BCI Groups 51 and 51R batteries feature physical dimensions of 9.375 x 5.0625 x 8.75 inches (23.8 x 12.9 x 22.3 cm), or at least very close to these dimensions.

Group 51 and 51R are usually made as vibration resistant Absorbent Glass Mat (AGM) Sealed Lead Acid (SLA) batteries that may easily fit most car battery compartments, intended for these batteries.

In order to fit more easily, some batteries are slightly smaller (as Group U1, for example, but still labeled as Group 51 batteries), leading to decreased weight, but also smaller capacity, cranking Amps and Reserve Capacity. But, these purposely built batteries are a much better option (they are optimized for certain purpose) for the intended application (Toyota Prius, Mazda Miata, etc.).

Also, to help with easier fitting, some batteries are manufactured as Group 51 (positive terminal to the LEFT) and as Group 51R (positive terminal to the RIGHT).

Anyway, the following table lists some of the most popular Group 51 and Group 51R batteries, with their most important features.

Note: Amazon links open in the new windows, feel free to check them for the most up-to-date prices and offers. Also, batteries marked with '*' are slightly wider than 5.0625 inches (12.9 cm) - they actually don't belong to Group 51 or 51R, but to the Group 22NF featuring size of 9.4375 x 5.5 x 8.9375 inches (24 x 14 x 22.7 cm), but they are often labeled as Group 51/51R batteries.

ACDelco ACDB24R Advantage AGM Automotive BCI Group 51 Battery

ACDelco ACDB24R is well balanced and very popular Group 51 battery, commonly used as an automotive battery, but it is also used for other purposes as well.

It may be used as starting battery and for cycling applications - it features 45Ah nominal capacity, 325 CCA Amps, 390 MCA Amps and 70 minutes Reserve Capacity (RC) and it weighs acceptable 29.1 pounds (13.2 kg).

ACDelco ACDB24R is also one of the best-rated group 51 batteries.

Deka/East Penn 8AMU1R AGM Battery

Deka/East Penn 8AMU1R AGM battery is an AGM battery intended primarily for starting/cranking applications.

It features 310 CCA Amps, 400 MCA Amps and 'only' 45 RC minutes, but it is very light battery weighing 25 pounds (11.3 kg).

Well designed battery with good ratings.

Delphi BU9051P MaxStart AGM Battery

Delphi BU9051P is a dual purpose battery featuring 46 Ah nominal capacity, 325 CCA Amps, 390 MCA Amps and 60 RC minutes. Also, it weighs 29.5 pounds (13.4 kg).

Delphi BU9051P is commonly used as an automotive and general-purpose battery, but it is not as popular as, for example, ACDelco battery.

Optima 8071-167 D51 and Optima 8073-167 D51R YellowTop Dual Purpose Batteries

Optima 8071-167 D51 and Optima 8073-167 D51R YellowTop are premium dual-purpose group 51 and 51R batteries.

They feature spirally wound cells, somewhat smaller 20h capacity of 38 Ah, but very good 450 CCA Amps, 575 MCA Amps and 66 minutes RC. They weigh 26 pounds (11.8 kg).

Optima 8071-167 D51 and Optima 8073-167 D51R YellowTop are used as automotive batteries, but they are also used for many other applications. If they are charged with battery charger, be sure to use smart AGM battery charger - this warning goes for all AGM batteries, not just for Optima batteries.

VMAXTANKS SLR60 Solar AGM Battery

VMAXTANKS SLR60 Solar AGM Battery is deep cycle battery with physical dimensions of 9.2 x 5.5 x 8.2 - basically, it belongs to the 22NF group.

Nonetheless, it is often labeled as group 51 battery and used interchangeably (if it can fit due to the somewhat larger width).

VMAXTANKS SLR60 battery features 60 Ah nominal capacity and 135 minutes Reserve Capacity. It weighs 43 pounds (19.5 kg).

As starting battery, VMAXTANKS SLR60 is not good - simply, it is not designed and intended for such applications. But, as deep cycle battery, it tolerates large number of charging/discharging cycles and is used in cycling applications, including off-the-grid applications (solar, wind turbine battery), kayak trolling motor battery, wheelchair battery and similar.

XS Power D5100 and XS Power D5100R XS Series AGM High-Output Batteries

XS Power D5100 and XS Power D5100R XS Series are labeled as group 51 and 51R batteries, but they are somewhat larger, featuring dimensions of 9.04 x 5.43 x 8.19 inches - practically, they belong to the Group 22NF batteries.

XS Power D5100 and XS Power D5100R XS Series are dual-purpose batteries and some of the best-rated batteries that belong to the Group 51/51R (or 22NF) batteries.

They are heavy (39.6 pounds, 18.0 kg), but they also feature 60 Ah nominal capacity, 745 MCA Amps, and 100 RC minutes.

Despite their price (after all, you get what you pay), XS Power D5100 and XS Power D5100R XS Series are very popular batteries, commonly used as group 51/51R batteries, if/when they can fit due to their larger width.

Long Story Short: Group 51/51R batteries are designed as starting/dual purpose/deep cycle batteries, intended for automotive, solar and other applications.

Note: Amazon affiliate links ('Model' column) open in the new windows, feel free to check them for the most up-to-date prices and offers.

When choosing the right model, be sure to pick the battery according to your own needs and requirements.