Group 29 vs Group 31 Batteries: An In-Depth Comparison

If you own any type of vehicle, you know the importance of your battery. It acts as the primary power source for your engine, not to mention it also powers all the various electronics in your vehicle.

Knowing the size of your battery is vital when it’s time to replace it. There are quite a few battery sizes available, but today, we’re only going to focus on two battery group sizes: 29 and 31.

You can also read our review on Group 29 and Group 31 batteries. You’ll also find information on their main features, specs, and uses.

Below is a detailed explanation between group 29 vs group 31 batteries.

Group 29 vs Group 31 Battery

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Group 29 vs Group 31 Battery

The main differences between group 29 vs group 31 battery are that generally a group 29 battery is lighter (28 -30 pounds vs 60 – 65 pounds), group 31 batteries are more powerful (75 and 125 Ah vs 60 to 80 Ah) and group 29 batteries are slightly smaller.

Not all vehicles aren’t created equally; neither are their batteries. Luckily, one organization made a standardized list of the physical dimensions of all batteries. Best of all, they’ve put it all in one convenient chart.

The Battery Council International (BCI) is a group of North American manufacturers and retailers. Whenever you’re in the market for a new battery, just check this chart to find the battery that best fits your vehicle.

Group 29 Battery

Group 29 batteries fall into two groups: 29NF and 29H. 29NF batteries have a flooded lead-acid electrolyte composition. One advantage is that they’re affordable. Yet, their downside is that they need to be frequently checked to make sure there are no electrolyte spills or corrosion.

The letter ‘H’ on the Group 29H batteries stands for ‘high capacity’. It also refers to the fact that this battery is a rechargeable Li. It may also refer to the battery’s high discharge rate.


  • Available as ‘NF’ or ‘H’ for enhanced performance and versatility
  • Lightweight
  • Available as lead-acid or lithium-ion for a variety of applications and added stability


  • Nominal capacity is relatively low
  • Group 29NF requires frequent maintenance

Group 31 Battery

Group 31 batteries are typically Absorbent Glass Mat (AGM) and Sealed Lead Acid (SLA) AGM/Gel. These are the two most common types because of their ease of use and reliable applications.

There are also lithium Group 31 batteries. These are becoming more popular because they’re lighter in weight. They’re also capable of providing more charging/discharging cycles. The downside is that they cost more than AGM/Gel batteries.


  • Offers top-notch low current discharge to increase battery life
  • High power ratings
  • Low-maintenance
  • Available as AGM/SLA and lithium


  • Some models are a bit pricey

Toe-to-Toe Comparison

Here’s a rundown of all the major points of comparison in our Group 29 vs. Group 31 review.


These are the average sizes of each battery group as specified by the BCI.

Group 29

The 29NF has dimensions of 13 x 5.5 x 8.93 inches, while the 29H battery measures 13.1 x 6.7 x 9.1 inches.

Group 31

The Group 31 batteries measure 13 x 6.8 x 9.4 inches. Compared with the Group 29NF, the Group 31 batteries are larger. Also, when it comes to the 29H batteries, the Group 31 are shorter, yet they’re also taller and wider.

The Takeaway

There’s only a slight difference between Group 31 and 29H batteries that comes down to about 0.125 inches in dimensions. As a result, some people prefer to fit in 29H batteries in the battery compartments designed for 31 batteries.

Power Ratings

The power capacity of any type of battery is an average measurement of the amount of electric current that the battery can provide over a certain amount of time. Here are some basic ratings of both battery groups when used in normal conditions.

Group 29

Group 29 lead-acid batteries have a nominal capacity of about 60 to 80 Ah. They have an outstanding rating of Cold Cranking Amps (CCA). It can be anywhere between 650 and 900 amps.

When it comes to their Reserve Capacity (RC), Group 29 batteries can provide an average of 190 to 220 minutes.

Lithium-ion Group 29 batteries have roughly the same power ratings as their lead-acid counterparts. The only difference is that they’re lighter and easier to handle. So, you get high power with less of the hassle of heavy batteries.

Group 31

Group 31 batteries have an average nominal capacity that ranges between 75 and 125 Ah. The CCA ranges between 600 and 1150 amps. Let’s not forget the RC value of this battery group. You’ll be happy to know it features a range of 155 and 240 minutes.

It’s important to mention that lithium Group 31 batteries supply almost the same amount of nominal capacity as lead-acid batteries. Yet, lithium batteries excel because they’re able to supply more charge and discharge cycles.

The Takeaway

Both lead-acid Group 29 and 31 batteries are better known and widely used. Yet, Group 31 tends to have higher power capacities when compared with the Group 29 batteries.

Lithium-ion batteries in both battery groups are more efficient and have a longer lifespan. Yet, they’re also more expensive.


There’s a slight difference in weight between Group 29 and 31 batteries. This is why some can be used interchangeably. Let’s find out how these two groups compare when it comes to their weight.

Group 29

Group 29 batteries usually fall into the same weight category. This ranges between 50 and 65 pounds. This substantial weight is only with lead-acid batteries since they’re made with heavy materials.

Lithium-ion Group 29 batteries, on the other hand, are much lighter. They’re made with metal lithium, which is known as the lightest metal on earth. Some are even as light as 25 pounds.

Group 31

Lead-acid Group 31 batteries usually weigh around 60 to 75 pounds. That’s much heavier than other types of batteries. This is because they consist of a liquid mixture of sulfuric acid and water, which adds to the battery’s overall weight.

On the other hand, lithium Group 31 batteries have an average weight of 28 to 30 pounds. This is a better option if you’re looking for a battery that can provide a decent amount of power without adding too much weight to your vehicle.

The Takeaway

The lightest batteries are Group 29 lithium-ion batteries. They weigh less, yet provide lots of power and high-performance.

Group 29 batteries can provide more than 1000 marine crank amps and over 100 minutes of RC. All that power comes in a lightweight package.


Since Group 29 and 31 batteries share similar dimensions, they can be used interchangeably.

Both of these types of batteries are categorized as heavy-duty commercial 12-volt batteries with six cells. They can start the engine and keep it running steadily. Plus, they can also run additional electronics in your vehicle, even with the engine turned off.

Group 29 and 31 batteries are used to power the following:

Trolling Motors

Electric trolling motors can usually be found on small and medium-sized fishing boats. They work to provide these marine vehicles with the thrust they need while trolling.

This makes them a good choice to be used to power electric trolling motors on marine vehicles. These types of motors usually provide a maximum current of 50 amps.

Another reason why these two battery groups are a good choice for trolling motors is their reduced capacity loss compared to lead-acid batteries. Plus, when used as trolling batteries, Group 29 and 31 batteries are utilized in applications where it’s essential to have lower mass, such as kayaking.

Automotive Batteries

Group 29 and 31 batteries make terrific automotive batteries. They may be used as dual-purpose batteries in a single battery electric system. These systems are found in cars and trucks, where the batteries power various electrical components.

They also can be used as a power source for dual-battery electric systems, which is more commonly found in RVs. In cases like this, the battery does the job of both a starting and deep cycle battery.

Here are other vehicles that can use Group 29 and 31 batteries:

  • Recreational Vehicles (RV) motorhomes
  • Campers
  • Trucks

The Takeaway

Both of these battery groups are powerful enough to run a wide range of engines. They’re also capable of running any number of accessories without the need for an engine to be running.

Group 29 vs Group 31 Batteries The Bottom Line

Any time you’re looking to replace your battery, the first thing you have to check is the dimensions. Thanks to the BCI, you have a ready-made chart for your convenience.

Our Group 29 vs. Group 31 battery analysis has all the information you need when buying your next battery. Whether you opt for lead-acid, AGM, or lithium-ion, the right-sized battery will do wonders for your vehicle by boosting its performance and keeping it in excellent condition.

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