Groups 51 and 51R Batteries - Dimensions, Features and Recommendations

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: April 15, 2024.

Group 51 and 51R Batteries Features and Specifications

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, smaller capacity, cranking Amps, and Reserve Capacity. But, these purposely built batteries are a much better option (they are optimized for certain purposes) for the intended application.

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).

The following table lists some of the most popular Group 51 and Group 51R batteries, as well as their most important features.

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Some of the most popular group 51/51R batteries include:

ACDelco ACDB24R Advantage AGM Automotive BCI Group 51 Battery

ACDelco ACDB24R is a well-balanced and very popular Group 51 battery, commonly used as an automotive battery, but it is also used for light industrial applications, etc.

It may be used as a starting battery and for cycling applications - it features a 45Ah nominal capacity, 325 CCA Amps, 390 MCA Amps, and 70 minutes Reserve Capacity (RC), and it weighs an 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 a 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, the 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, a 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 a battery charger, be sure to use a 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 a deep cycle battery with physical dimensions of 9.2 x 5.5 x 8.2 - basically, it belongs to the 22NF group due to somewhat wider body.

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

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

As a starting battery, VMAXTANKS SLR60 is not good - simply, it is not designed and intended for such applications.

However, as a deep-cycle battery, it tolerates a large number of charging/discharging cycles and is used in cycling applications, including off-the-grid applications (solar, wind turbine battery), kayak trolling motor batteries, wheelchair batteries, 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.

XS Power D5100 and XS Power D5100R XS Series are not as common as some other group 51/51R batteries.

Group 51 Battery Alternative

If you are looking for group 51/51R batteries, they can be found online and in local shops and stores.

However, if you really need one but you can't find it, there are a few battery groups that are very close in size, including:

• 51/51R battery dimensions (L x W x H): 9.375 x 5.0625 x 8.75 inches (23.8 x 12.9 x 22.3 cm),
• U1/U1R battery dimensions (L x W x H): 7.75 x 5.1875 x 7.3125 inches (~19.7 x 13.2 x 18.6 cm)
• 22NF battery dimensions (L x W x H): 9.4375 x 5.5 x 8.9375 inches (24.0 x 14.0 x 22.7 cm).

As one can see, U1/U1R battery group is shorter and lower, but just a little bit wider. Because of that, this battery generally may fit battery compartments intended for group 51/51R batteries, but due to smaller dimensions, these batteries are also somewhat weaker in terms of CCA/MCA ratings.

22NF batteries are larger than group 51/51R batteries, but most of them are designed as deep-cycle batteries and are NOT suitable as replacements for group 51/51R batteries.

How to Charge Group 51/51R Battery

When the battery is part of car's electrical system, let the onboard alternator and charge controller do their task of charging the battery.

However, if there are issues with the battery or the battery was used outside of the vehicle, it is recommended to use an advanced AGM battery charger with a maximum charging current of ~5A.

Note: Group 51/51R batteries are designed to accept charge well, but just in case, when charging them on the bench, don't overload them with excess charging current. Just my 2c.

One of the most popular battery chargers in this class is the NOCO Genius5 6V&12V 5A Smart Battery Charger.

NOCO Genius5 is designed to charge various 6V and 12V lead-acid batteries (wet/flooded, AGM, Gel) and to recover deeply discharged lead-acid batteries.

Also, it can be used to charge 12V lithium (LiFePO4) batteries, to act as lead-acid battery desulfator, maintainer, etc.

For more information and up-to-date offers and prices, feel free to check the NOCO Genius5 6V&12V 5A Smart Battery Charger Amazon link (link opens in the new window).

How to Dispose of Group 51/51R Batteries

Proper disposal of Group 51/51R batteries, which are commonly used in vehicles, is crucial for both environmental protection and public health. These batteries contain hazardous materials such as lead and acid that can be detrimental if not handled correctly.

• Understand the Hazard: Group 51/51R batteries are lead-acid batteries and must be treated as hazardous waste. The lead and sulfuric acid inside can be harmful to the environment and human health if released into soil or waterways.
• Use Protective Gear: When handling old batteries, always wear protective gloves and safety goggles. This protects you from acid leaks and lead dust, which can be harmful upon contact.
• Transport Safely: Before transporting the battery, ensure that it is stable and upright. Place it in a plastic bag or a secondary container to catch any accidental leaks. Secure the battery in your vehicle to prevent it from tipping over during transit.
• Recycle the Battery: The most environmentally responsible way to dispose of a Group 51/51R battery is through recycling. Lead-acid batteries are highly recyclable, with more than 95% of the battery’s materials being reusable. Here's how to recycle them:

• Battery Retailers and Auto Shops: Most places that sell car batteries also offer recycling services. When you buy a new battery, you can usually leave your old one at the store for free or a small fee.

• Municipal Recycling Centers: Many local waste management facilities have specific protocols for handling lead-acid batteries. Contact your nearest center to inquire about drop-off procedures.

• Specialty Recycling Services: Look for companies that specialize in hazardous waste collection and recycling. These services can handle large volumes or corporate disposals.

• Avoid Regular Trash or Landfills: Never throw a lead-acid battery in the regular trash or dumpster. This is illegal in many jurisdictions due to the hazardous materials in the batteries.
• Document the Disposal: If you are disposing of batteries as part of a business, keep records of how and where the batteries were disposed of. This documentation can be important for compliance with local regulations and can help in corporate sustainability reporting.

Properly disposing of Group 51/51R batteries involves taking precautions to handle them safely and ensuring they are recycled appropriately.

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

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