Group 27 Battery [Uses, Size, and Replacements]

By:Michael Johns

Group 27 battery

On this page, you will find all the information you need about group 27 batteries.

If you’re looking to replace your battery then it’s important to check your replacement correctly fits your vehicle or electrical system.

You can find many different brands and types of group 27 and 27F options on the market. Below we will go through the dimensions, uses, and equivalents to bring you up to speed on the subject.

⚡BCI Group 27 Key Facts⚡

  • Length: 12 1/16 inch
  • Width: 6 13/16 inch
  • Height: 8 7/8 inch
  • Weight: 50 lbs
  • 70Ah – 90Ah
  • 800 – 950 CCA
  • Starting, Marine

What is a Group 27 Battery?

Group 27 batteries are usually built for marine and deep cycle uses. The most common type is a hybrid dual purpose battery or ‘marine’. As you would expect, this means they are used on boats to start engines and cyclical application for low current electronics.

You find these 12V batteries in boats, trolling motors, and electric vehicles. Plus they are used in commercial backup situations like oil fields and similar industrial situations.

They are quite large compared to similar group sizes in its class. This enables manufacturers to deliver a balanced performance of Amp-hour (Ah) capacity and Cranking Amps (CA).

You see capacities of 70Ah to 90Ah combined with more than 900CA. These attributes allow you to draw a high current to start an engine and run for long cycles at a low current. 

A small selection of car starting group 27 batteries are also available from brands like NorthStar.

Group 27 Dimensions and Weight

The dimensions of group 27 batteries are:

  • Length: 12 1/16 inches (306mm)
  • Width: 6 13/16 inches (173mm)
  • Height: 8 7/8 inches (225mm)
  • Average weight: 50lbs (23kg)
Group 27 dimensions

Group 27F has the exact same dimensions but the terminal poles are laid out in the opposite location to fit automotive cars. F means reverse polarity so the terminals are opposite. You’ll notice that the positive terminal is on the right side rather than the left.

Application and Cell Type

The most common group 27 cell type is lead acid AGM (Absorbent Glass Mat). This gives you a maintenance free experience. Plus they are durable in boats and commercial environments as they can withstand vibrations and bumps.

You can also find flooded WET and Sealed options but these are less common.

Now there is a growing amount of lithium or ‘LifePo4’ equivalents. BCI groups sizes only refers to lead acid batteries but manufacturers try to make lithium equivalents in the same dimensions. The lithium phosphate cells offer higher energy storage density and are lightweight. This means they should have a higher Ah storage capacity. The only downside is that they struggle to pull high currents.

boats on a lake
Group 27 are often built for marine use

Most often group 27 are used for marine and dual purpose application of engine starting and deep cycling. The capacity ranges from 70Ah to 100Ah along with 800CCA to 950CCA.

You can find a number of dedicated deep cycle or starting group 27 batteries. These are more rare, particularly for starting due to the extra size and weight. You might see them in larger trucks and buses for starting.

Pros and Cons of Group 27 Batteries

Let’s look at the advantages and disadvantages of these batteries. 


  • Extra size allows for hybrid application
  • High Ah capacity upto 100Ah
  • High starting capacity over 900Ah
  • AGM cells are maintenance free, long lasting and durable
  • Wide choice of hybrid/marine options


  • Heavy
  • Larger dimensions than similar group
  • Few equivalents or replacements
  • Rare to find as starting batteries

Group 27 vs Group 24 Batteries

There are subtle but important differences between group 27 and 24 batteries.

The first thing to be aware of is the size difference. In particular, group 24 batteries are shorter in length by 2 inches. Although, the width and height are very similar.

A group 27 battery is 12 inches long, while a group 24 is 10 inches in length.

This increased size leads to a higher weight and maximum capacity. Group 24 is limited to around 80Ah, while group 27 often reaches upto 100Ah.

In addition, the CCA increases too, with group 27 reaching 850 to 900 CCA, compared to 600 – 800CCA produced by group 24. 

When it comes to the cells and application of the two batteries, this remains similar. You’ll usually find them in lead acid flooded WET or AGM. Plus lithium options are available with these dimensions. 

Both types are often built for marine and hybrid use. Plus you’ll find a larger number of deep cycle 24 groups available. As starting batteries, both are rare to find but not impossible.

Group 27 vs Group 31 Batteries

Group 31 batteries are bigger and more powerful than group 27.

In physical dimensions, they are 1 inch longer and ¾ of an inch taller. While this doesn’t sound like a huge amount, it produces a noticeable difference in performance. 

Group 27 battery capacity tops out at 100Ah while group 31 reaches 125Ah. Adding to this, for starting an application a group 31 can provide 1250 CCA, whereas group 27 offers around 900CCA.

While they are both produced as lead acid flooded and AGM, and lithium, they are used in different scenarios. Group 31 are found in heavy duty commercial applications such as truck engine starting or high-capacity deep cycle and hybrid use in RVs and boats.

Comparatively, group 27 tends to be restricted to being a mid-sized marine application or commercial backup.

Group 27 vs Group 65 Battery

Group 65 batteries have similar dimensions as a group 27 so you might wonder if it can be used as an equivalent replacement. 

They are both the same length at 12 inches. But group 65 is shorter by over 1 inch and wider by ½ an inch. You should measure your battery compartment carefully to check it can fit!

As you already know, group 27 are usually made as hybrid dual purpose batteries. This is the same for group 65 which means both are commonly used in marine application.

Adding to this, the capacities are very similar. Group 65 has a lower maximum cyclical capacity at 75Ah but can reach the same maximum starting energy at 950CCA.

All of these similarities mean that you can consider the two types to be an equivalent replacement.  


Are all Group 27 batteries the same size?

Yes, all group 27 batteries should have the same (or close to) the exact same dimensions. This means you can swap batteries in the same group no matter where they are made or the manufacturer. The only thing to watch out for is the positive and negative terminal locations.

Which vehicle uses a group 27 battery?

They are not found in very many modern cars. They are rare as starting batteries except in some older US made cars or Hondas. You will more commonly see them in boats.

How many amp hours is a group 27 battery?

Group 27 batteries have an energy storage capacity of 70Ah to 90Ah

How long will a group 27 deep cycle battery last?

A lead acid deep cycle battery should last between 6 to 8 years and 500 to 1000 cycles. The exact number will change based on the internal battery chemistry. For example, modern lithium batteries last much longer!


That’s it, all you need to know about group 27 batteries. 

As you have discovered, these are generally manufactured as AGM batteries for marine application giving a balance of starting power and deep cycle ability. In addition, you can find dedicated starting or deep cycle options too. 

They are comparatively larger and heavier than many BCI group batteries in a similar class. If you’re looking at equivalent group replacements then you can look at group 65 that have similar attributes.