27 vs 31: Difference Between Group 27 And Group 31 Batteries

Battery makers have made buying a battery for a car, RV, or trailer more of an adventure. Not only do you need the right voltage to get everything to work but you also need the right group size. 27 and 31 are the two most common group sizes out there.

The biggest difference will be their sizes. The Group 27 battery is smaller than the Group 31 model. That means that if you buy a larger battery, you may have to make alterations to your battery box and other equipment.

To learn more about this topic, just continue to read our article. It has the information you want to know about so you can buy the right battery for your camping situation. Take a few minutes to see how this information helps you.

Difference Between Group 27 And 31 Batteries

Category Group 27 Group 31
Size 12.1 x 6.8 x 8.8 inches 13 x 6.8 x 9.4 inches
Weight 54 to 70 pounds 25 to 85 pounds
RC 1440 to 220 minutes 150 to 250 minutes
CCA 600 to 1000 750 to 1250
Capacity 18h 20h

** figures taken from https://powercurious.com/group-27-vs-group-31-battery/

As you can see there are a lot of differences between these two batteries. The Group 31 is bigger, holds more power, and lasts longer than the Group 27 option. That makes the Group 31 battery the superior one.

But, with a larger and more powerful battery, you may have to spend some money re-configuring your battery space. The boxes may not hold the Group 31 unless they were already large, to begin with.

One owner spent about $600 altering his battery situation when he added another battery to his system. Before you buy, you need to look at the whole picture and see what you have to do and how much it will cost.

Then think about your purpose for these batteries. The Group 27 is often used in high-performance cars as well as hybrids and electric vehicles. The Group 31 battery has a more versatile purpose.

They are used for off-grid solar power collection, UPS devices, golf carts, and more applications.

Group 31 vs Group 27 Battery Size


The chart shows you the biggest difference between these two batteries. The fact that the Group 31 has one extra inch in length and .6 more in height can mean it won’t fit in your designated places.

This is something you have to consider before making your purchase. Will the battery fit in your current battery box? If not, then you may have to go to the expense of replacing that box even if you are merely adding a second battery to your system.

With that addition, you may have to add in some other parts including a new vent, cables, and other electric parts. Once you have added this battery to your system, proper maintenance and use will allow it to last for many years.

Being stronger does not mean it does not need any maintenance. The only way to avoid making wholesale changes to your battery box, etc., is to buy a Group 31 battery that is smaller than the Group 27.

There are smaller sizes of the Group 31 battery so make sure to shop around before you buy.

Group 27 vs 31 Amp Hours


This will depend on the brand and type of battery you buy. For example, a Group 2 VMAX battery offers you 110 amp hours while the Banshee option only offers 77 amp hours.

On the other hand, different Group 31 batteries offer between 100 and 200 amp hours. Make sure you read the labels of the different brands to make sure you are getting the power you need.

Then all these figures are estimates only. That is because the discharge rate, the temperature, and even the maintenance play a role in how many amp hours you will receive at any given time.

All those figures do is give you an idea of how much power you can use without recharging before the battery will go dead. This rough idea will allow you to figure out your usage if anything goes wrong and you cannot recharge at the moment.

Group 27 vs 31 Battery Weight


The chart above gives you the approx. weight of each group’s batteries, There is a range because the sizes of the batteries in each group may not be the full dimensions given in the size category.

As you have read, the Group 31 battery can come in different sizes with some being smaller than the Group 27 listed in that chart. Do some careful shopping and check all the specs as you may be able to get a lighter battery without sacrificing any power.

One thing to remember to do is check the lengths of your battery cables. It is possible that the terminals on each battery group may not be in the same place. That means your cables may either be just right, too short, or too long for your set up.

The location of your battery will play a role in the length of the cables. Make sure to measure carefully so you do not end up with the wrong size of cables. These are the little details you have to watch out for when you are thinking of making a change in the batteries or adding more to your system.

Some Final Words

By all standards, the group 31 battery is the better of the two for most applications. It just may not fit in your car’s, RV, or trailer's battery tray or box. Make sure to measure your box to see how much room you have to work with.

If it is not much, you may be able to go to a smaller size and still get the same power. Do some comparison shopping as well to see if you can find one or the other on sale. It does pay to look for deals.

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