Groups 51 and 51R Batteries: Compare and Recommendations

Published on: May 15, 2022
Written by Liam Jaxon / Fact-checked by David Rowan

This is a common answer of “how does a group 51 or group 51R battery reacts on the instant starting”. Moreover, a 51 and 51R battery is a breeze for working with any type of automotive applications, yet it weighs a lot. Almost all 51 and 51R AGM batteries have in-built possible features to improve your engine empowering functioning system whether the weather is sunny or passing through heavy snowy winter. People sometimes get confused group 51 vs 51R battery.

In general, it depends on the choice of terminal and requirement of the vehicle including other features. However, an easy solution is better to find out the real vehicle need. Apart from that if your car is showing multiple signs of failure even after installing the right battery as the manual says, then this is a malfunction or needs a substitute to overcome the failure. 

groups 51 and 51r batteries

Suppose, if you have installed a 40V battery without knowing that how the battery works and how much battery voltage can be integrated with it? Well, in that case, all about 40V battery charging power you can study. Each battery is meant to be used as per their vehicle battery replacement demand even, check a quick study Battery Cross Reference Chart: Compare Dimensions & Specifications.

Whether BCI 51r holds a positive terminal on the front of the reversed in 51, if you need a perfect replacement, give a thorough reading of group 51 and 51r batteries which are full of different subjected battery models, their comparison, and recommendations from the real experience.  

Group 51 and 51R Battery: Features and Dimension 

When your personal car or public transport requires the perfect match of battery in terms of interchanging or size replacement, group 51 and 51R batteries provide almost similar dimensions as if 9.3 x 5.0 x 8.75 inches (Length x Width x Height), or 238 x 129 x 223 mm. Whether a group 78 battery is compatible with American cars only, a group 51 and 51R is a good choice as they accept both US and Japan cars and hondas. 

The availability, if we try to explain, is very familiar with dual-purpose and automotive starting. Such automotive brands, for instance, Honda, Mazda, Nissan and the other US and Japanese vehicles. But we highly recommend manufactures’ manual reading to ensure the battery size. 

Speaking of the weight of both group 51 and 51R, not less than 9 and a half pounds which let you fix, yet not carry easily anywhere. If we think about both groups’ Lithium-ion battery construction, of course, it weighs less because of the functional behavior that a powerful yet lightweight and high electrolyte-filled battery does.

As per our experience, we have seen Nissan GTRs accept 51R Lithium-ion batteries in themselves, however, the cold-cranking amps will not exceed 850. But somehow it takes more than an hour to compile the solutions. 

If we consider any 12V battery type to include it in group 51 battery, then it must be an AGM battery to continue the rest of the engine and a well-thinking about your car and hondas, you should never justify. Also, easy tasks, like recharging fast to take it for a long time and not more than 20% fastest recharging battery is a plus point in your easy access-group 51 and 51R AGM batteries. 

Groups 51 and 51R Batteries: Features and Recommendations

ACDelco Gold B24R AGM BCI Group 51 Battery

Technical Specification 

Chemical Lead-acid 
Weight 31.5 pounds 
Dimension 18.5 x 11.4 x 9.5 inches
Voltage 12V
Operating temperature 32°F and 70°F

We chose ACDelco Gold B24R as the first choice, why? Among other batteries of groups, 51 and 51r that we have tested are not common and refer to a proper manual before opening the box. In the meantime, we fall in love with its construction which we call a durable design with a double-wall to protect the inner electrolyte. Such a lead-acid battery is the worst enemy for truck batteries.

Compared to regular flooded batteries, the construction holds Calcium Alloy to generate a fine grain. Besides making a corrosion-resistant grid, minimizing water consumption and maximizing cycle life. A fully charged ACDelco Gold B24R is a blessing that can store in an upright position at a temperature range between 32°F and 70°F  (OCV is >12.5).


  • Easy and fast installation;
  • Easy manual guide;
  • Fast charging;
  • High resistance to vibrations;
  • Durable. 


  • Hefty-priced. 

Delphi BU9051P AGM Premium Automotive 51R Battery

Technical Specification 

Chemical Lead-Acid, AGM
Weight 29.5 pounds 
Dimension ‎9 x 7.7 x 4.8 inches
Voltage 12V
CCA 325
RC 60

We put Delphi BU9051P in second position. Rather than the previous group 51 battery, this one concludes with rough and tough construction made with Absorbed Glass Mat high-tech. Not only provides a better life cycle but also recharges fast. If you are aiming for a battery of BCI 51 which is safer and more connected, this is the one to rely on. 

It also covers a range of Cold Cranking Amps, however, not the maximum number though. With only 60 reserve capacity, CCAs ensure the car starts instantly. However, RC holds the main responsibility to run power accessories. No tolerance with vibration and corrosion.


  • More resistant to vibration;
  • Affordable;
  • Lightweight compared to the previous model;
  • High cold-cranking amps;
  • Improved cycle life. 


  • Nothing noticeable. 

Optima OPT8071-167 D51 Dual Purpose Battery

Technical Specification 

Chemical Lead acid 
Weight 19.36 pounds 
Dimension 9.21 x 4.98 x 8.94 inches
Terminal SAE 

Optima always provides an optimistic different group of batteries, BCI 51 and 51R group of batteries take it to the next level. This model provides deep-cycle power during the instant start of your motorcycle, car, and other vehicles. Optima keeps a promise to extend a BCI group 51 battery’s life 3x longer.

To make the promise strong, Optima has provided extreme construction, for instance, entirely and externally built-in Alloy material containing lead-acid electrolytes. As long as the sealed battery has no overflows, it can serve properly. 

Though the brand ensures zero maintenance before and after installation of the battery, we prefer short time maintenance after every drive. We tested a clean power source including Faster recharging and 300+ discharge/recharge cycles. However, rather than spillproof construction, mounting position capacity we have experienced less. 


  • Deep cycle power;
  • spiral-wound cells;
  • coating of lead oxide;
  • automotive and RV underhood starting;
  • Compatible with diesel vehicles. 


  • Hefty-priced;
  • Less mounting advantage. 

Optima OPT8012-021 D34 Dual Purpose Battery

Technical Specification 

  • Size: 10″ x 6 7/8″ x 7 13/16″ tall;
  • Weight 42.9 pounds;
  • Dimension 10 x 6.88 x 7.8 inches;
  • Voltage 12;
  • Terminal  SAE;
  • Deep-cycle and cranking power;
  • Reserve Capacity 120.

Tougher than any road you are on or off, with this vision, Optima has manufactured a true dual-purpose automotive battery to give you the advantage of knocking around. Remembering the unstoppable power for extreme enthusiasts, for instance, trucks with winches and sometimes including high demand audio systems provides higher deep cycle and cranking power than the previous Optima model.

Speaking truth about the core construction has individual spiral-wound cells which are legal and powerful double lead plates. Both of the plates are coated plates in a coating of Lead Oxide, whether one holds a positive terminal and another is a negative one. Though traditional flat plates of AGM batteries are not expensive with pure materials, custom automated cell winding machines in this model differentiate the level. 


  • Up to 3x longer life and maintenance-free;
  • More than 15 times the vibration resistance;
  • Spill Proof, mountable in virtually any position;
  • Faster recharging and 300+ discharge/recharge cycles.


  • No cons.

VMAX SLR60 Group 51 Battery

Technical Specification 

Chemical Lead acid 
Weight 30 pounds 
Dimension 9.21 x 5.5 x 8.94 inches
Voltage 12V

Last but not least, one has been manufactured by the well-reputed VMAX Solar manufacturer. However, the second-heaviest one in our listing. The main fact is this is a maintenance-free option. If you are lazy to take care of your car battery is draining or not, nothing can beat such a nice group 51R battery. 

However, we found it more useful while the charging option is versatile, for instance, chargeable from electricity, gas, and solar energy. Meanwhile, an afloat service plan from the manufacturer ensures longer battery life with 99% of recombination capabilities and neither fumes nor gas while it is getting charged. Since the signature bulky battery we found, it remarks a negative side.  


  • Maintenance free;
  • Compatible with every recharging energy;
  • Recombination capabilities. 


  • Heavy-duty;
  • Hefty-priced. 

Editor’s Note 

According to our experience, we recommend ACDelco Gold B24R as we have put it in the first position. Why? As mentioned earlier, this model has robust construction including the operating temperature as if 32°F and 70°F  (OCV is >12.5) is a great plus point. 

Compared to this model, Delphi BU9051P is lighter, yet the prospective users may be able to work with it because the temperature compatibility for tasks is regular. However, we found it much more befitted in terms of easy installation and more resistant to vibration. Since Optima OPT8071-167 is rather lighter than the previous model, we found it affordable too to perform our cars and motorcycles as a prospective deep cycle battery as a BCI group 51 or 51R.

If it is a turn for Optima OPT8073-167, we have to think about the next and last enlisted group 51 and 51r subjected battery model too. Why? Because most of the features are similar, yet the affordability is quite different. Also, if we choose the 4th model, we may have lightweight, strong cranking, maintenance-free and high power features in a well-built and perfect brand to meet all your car requirements to give an instant kickstart. 


What Is the Range of Group 51R Battery Cold-Cranking Amps? 

What do we know about cold-cranking amps? Well, this is a feature that produces a short burst of power while giving an instant start to your car. After this little burst of power, an alternator inside it will recharge the car’s battery. However, BCI group 51R cold-cranking amps (CCA) range between 450-600, yet some contain less than this amount. 

Is Group 24F a Replacement of Group 51R?

Not all batteries but a few batteries are compatible with group 24F batteries as a replacement of group 51R if it is not available in the shop. In general, a group 51R AGM battery is available in Japan and US. However, a taller group of batteries leads to the possible replacement with a shorter size battery. 

The main issue can happen with a narrower frontend which may not create a secure connection in a wider battery holder. If you can change the battery tray, all possibilities may turn to possible. 

Are 51R and 51 the Same Battery?

Both BCI 51 and 51R batteries feature the common dimension that they include in construction, for instance, 9.374 x 5.0625 x 8.8125 inches (23.8 x 12.9 x 22.3 cm) or often very close to this dimension. However, in terms of advantages and installation compatibility and the car, it is great to install for, for instance, Toyota Prius, Mazda Miata, and more are the perfect match whether you choose group 51 battery or 51R.

In BCI group designations, R symbolizes a positive terminal on the right side of a battery, and while differentiating group 51 and 51R battery, BCI 51 has the letter on the right side. 

But as long as we have experienced, such a group 51 battery is often higher-powered in terms of recharging or interchangeability with a group 78 battery. If we try to find a good match for group 51R batteries, intending to install in shorter space, a group U1 we can consider as long as users can too. 

What Car Takes a 51R Battery?

The group 51R in is common to previously installed in well-reputed Hondas, Nissan GTRs, and some other Japanese Cars. why? Because the lightweight feature is rather bulkier in a 51 group battery. 

In general, the group 51R AGM battery has a narrower front to back to keep it clean and smoother while starting your vehicle. Moreover, among 90% used cars and other vehicles installed 7 categorized batteries, group 51R is one of the lightweight dimensional fit for those worldwide used vehicles.  

After the installation of a Larger Battery in Your Car, What Will Happen?

Well, most of the cars, almost 90% cars use 7 multipurpose deep cycle or general batteries with Lead-acid, Flooded, Gel Cell inserted electrolyte batteries to give a good start while they are aiming for personal transport.

For example, groups 34, 34/78, 27, 78, and more like T, H and U1. However, instead of purchasing a branded battery, better know the dimension because if you put the wrong battery that can lead to multi-purpose issues. 

Besides a proper replacement, if you are giving a try of interchange with other similar batteries, please check the OEM brand, CCA, RC, and other features.   

Final Words 

Among a few choices regarding 51 and 51R group batteries, select that one model which is long-lasting and very much compatible with your car battery tray holder. Though durability is the first point we consider, the rest are operating temperature, CCA and reserve capacity, amps range, and some useful features. 

With the batteries we have enlisted, each and every model are well-informed according to our experience. Since users’ entire choice solely depends on driving conditions and the environment, 51 and 51R batteries are common electronic accessories to handle your car and other transports. We prefer AGM and Lead acid-containing dual-purpose batteries are the real hero. Hence, our compiled and drastic information may work out soon as per your requirement. 

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About This Writer

liam jaxon author pic

Hi, I am responsible for the 'Homeowners Power Solutions' category. My name is Liam Jaxon and a licensed technician with 7 years of experience in vehicle batteries, electrical gadgets, and home appliances. My working experience in different residential & light commercial electrical sectors and the automobile industry helped to acquire vast knowledge in this industry.

Hi, I am responsible for the 'Homeowners Power Solutions' category. My name is Liam Jaxon and a licensed technician with 7 years of experience in vehicle batteries, electrical gadgets, and home appliances. My working experience in different residential & light commercial electrical sectors and the automobile industry helped to acquire vast knowledge in this industry.

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