Complete Guide to Group 31 Batteries: Dimensions, Features, and Types
LiTime Team
—
24/08/2025
Group 31 batteries are a go-to option for powering heavy-duty vehicles and equipment. Known for their durability and capacity, they’re commonly used in commercial trucks, RVs, boats, tractors, and other applications that demand consistent, long-lasting energy.
In this guide, we’ll explore the essential features, advantages, and important factors to consider when choosing a Group 31 battery.
Understanding Group 31 Batteries
Group 31 batteries belong to the Battery Council International (BCI) size classifications, which define standardized dimensions for automotive and industrial batteries. Built to provide high-performance power, these batteries are well-suited for heavy vehicles and equipment, making them ideal for demanding applications and long operating cycles.
Features of Group 31 Batteries
Size and Dimensions:
Group 31 batteries generally measure around 13 inches in length, 6.8 inches in width, and 9.4 inches in height. Their larger size translates into greater capacity, delivering ample power to handle heavy electrical loads and extended use.
Amp-Hour (Ah) Rating:
Group 31 batteries generally measure around 13 inches in length, 6.8 inches in width, and 9.4 inches in height. Their larger size translates into greater capacity, delivering ample power to handle heavy electrical loads and extended use.
Compared to Group 24 batteries, which typically provide 70–85 Ah (ampere-hours) at a 20-hour rate, Group 31 models deliver significantly more—usually in the 95–125 Ah range at the same rate. This higher capacity makes them well-suited for power-intensive applications that demand longer runtimes and consistent performance.
Thanks to their higher Ah ratings, Group 31 batteries can reliably sustain greater energy demands over longer periods, ensuring steady, uninterrupted power supply.
Types of Group 31 Batteries
Group 31 batteries come in various types, including Flooded Lead Acid Batteries (FLA), Absorbent Glass Mat Batteries (AGM), Gel batteries, and Lithium-ion (LiFePO4) options. Each type offers distinct features that cater to the specific needs of users in different situations. In order to better understand these batteries, let's delve into each type and its own specific features and advantages:
1. Group 31 Flooded Lead Acid Batteries
Flooded lead acid batteries (FLA), a type of Group 31 battery, require regular maintenance, such as monitoring corrosion levels and replenishing electrolyte levels, to ensure optimal performance. Without proper maintenance, the already limited lifespan of these batteries will be further reduced. Additionally, they need to be consistently charged to prevent damage. While flooded lead acid batteries may offer short-term cost savings, they ultimately end up costing more in the long run, especially when compared to lithium batteries.
1. Group 31 Flooded Lead Acid (FLA) Batteries
Flooded lead acid batteries are the most traditional type of Group 31 battery. They require routine upkeep—such as checking electrolyte levels, topping up with distilled water, and monitoring for corrosion—to maintain reliable performance. Without proper care, their already shorter lifespan can be reduced even further. While they are typically the most affordable option upfront, long-term costs can add up, especially compared to more durable alternatives like lithium batteries.
Pros
Lowest upfront cost among Group 31 batteries
Easy to find and widely available
Can deliver high bursts of current
Cons
Require frequent maintenance (watering and corrosion checks)
Risk of spills and leaks if mishandled
Not fully sealed, leading to electrolyte loss and corrosion
2. Group 31 Absorbent Glass Mat (AGM) Batteries
AGM batteries use a fiberglass mat to absorb the electrolyte, making them spill-proof and maintenance-free. They can be mounted in almost any position and are more resistant to vibration than FLA batteries. With proper care, AGM batteries typically last up to six years, offering a longer service life and better deep-cycle performance.
Pros
Maintenance-free (no need for watering)
Strong deep-cycle performance
Handle high discharge rates effectively
Excellent resistance to vibration and shock
Cons
Higher cost compared to FLA batteries
Can suffer damage if consistently overcharged
Slightly less energy storage capacity than FLA
3. Group 31 Gel Batteries
Gel batteries suspend their electrolyte in a gel-like substance using silica, making them stable and effective in extreme conditions. They excel at deep cycling and perform well in high temperatures, though they tend to be more expensive than AGM batteries.
Pros
Outstanding vibration resistance (great for marine and off-road use)
Good recovery from deep discharges
Maintenance-free, sealed design
Cons
More costly than both FLA and AGM options
Lower energy density than AGM
Sensitive to charging voltages and temperature extremes
4. Group 31 Lithium Batteries (LiFePO₄)
Lithium Group 31 batteries represent the premium choice, offering a wide array of advantages. They are lightweight, compact, fast-charging, and virtually maintenance-free. With a lifespan exceeding 3,000 cycles—and in some cases, such as advanced LiFePO₄ batteries, reaching 4,000–15,000 cycles—they far outlast other chemistries.
Most come with a built-in Battery Management System (BMS) for enhanced safety, protecting against overcharge, over-discharge, and short circuits. They also have a very low self-discharge rate, making them ideal for seasonal or backup use. Thanks to their efficiency and stable power delivery, they are particularly valuable in critical applications that require uninterrupted power.
Pros
Exceptionally long lifespan (thousands of cycles)
Lightweight and compact design for easy installation
High energy density with consistent output
Fast charging and high efficiency
Maintenance-free with advanced safety features (BMS)
Cons:
Generally more expensive upfront.
Requires a specialized charger.
Applications of Group 31 Batteries
Thanks to their high amp-hour (Ah) ratings, strong deep-cycle capabilities, and durability, Group 31 batteries are used across a wide range of demanding applications:
Automotive – Commonly installed in semi-trucks and heavy-duty vehicles, providing reliable starting power and energy for multiple onboard accessories.
Marine – Ideal for boats and other marine equipment, as they withstand vibration and shock while delivering dependable deep-cycle performance.
Off-Grid Systems – Frequently used in solar and wind power setups to store renewable energy for later use.
RVs and Campers – Power appliances, lights, and electronics in recreational vehicles, supporting extended off-grid living.
Emergency Backup Power – Serve as dependable backup energy sources for homes, offices, or critical appliances during outages.
Industrial & Commercial Use – Deployed in forklifts, construction equipment, and other heavy machinery that demands long-lasting, stable power.
Key Considerations When Buying a Group 31 Battery
Compatibility – Confirm that the battery matches your vehicle or equipment. Check terminal type, voltage, and physical dimensions to ensure proper fit and seamless installation.
Maintenance Requirements – Some batteries, like flooded lead acid models, require routine upkeep such as electrolyte checks and corrosion cleaning. Maintenance-free options like AGM, Gel, or Lithium eliminate this need.
Brand Reputation & Warranty – Choose established brands known for reliable performance. Look for warranties that reflect confidence in product quality.
For example, LiTime has over 10 years of experience producing high-quality lithium batteries at competitive prices. Their Group 31 batteries include:
5-year warranty with dedicated technical support
User-friendly return policy and responsive service (within 24 hours)
Clear operation manuals and online resources for easy installation and use
Best Recommended Group 31 Batteries
1. LiTime 12V 165Ah Group 31 Bluetooth Battery
The LiTime 12V 165Ah Group 31 LiFePO₄ battery is an excellent choice for users who need greater capacity and higher power output. Unlike standard Group 31 batteries, it delivers 65% more capacity without increasing in size, offering significantly longer runtimes for appliances. This makes it one of the highest-capacity Group 31 batteries available today.
Equipped with a high-performance 165A Battery Management System (BMS), it provides up to 2112W of peak power, easily supporting heavy-duty devices such as air conditioners, microwaves, and coffee makers.
In addition, the built-in Bluetooth 5.0 module allows users to conveniently monitor key metrics—including voltage, capacity, state of charge (SOC), and charging/discharging status—in real time through a smartphone app.
2. LiTime 12V 140Ah Group 31 Deep Cycle Battery with Bluetooth
The LiTime 12V 140Ah Group 31 deep cycle lithium battery combines advanced performance with smart monitoring via Bluetooth 5.0, making it a standout option for reliable outdoor power. With 40% more capacity than a standard 100Ah lithium battery, it provides extended runtime for RVs, trolling motors, and solar systems—perfect for off-grid adventures.
Its 150A BMS ensures dependable power delivery for larger appliances like coffee makers and electric griddles, allowing you to enjoy household comforts on the go. Designed for durability, the advanced BMS offers 20+ layers of protection, including safeguards against overcharging, over-discharging, over-current, short circuits, and extreme temperatures. Added features such as pre-charge functions, auto-recovery from overload, and enhanced resistance to moisture and salt spray make it equally suited for marine environments.
3. LiTime 12V 100Ah Group 31 Bluetooth Battery
The LiTime 12V 100Ah Group 31 lithium battery combines smart technology with reliable performance. Its Bluetooth 5.0 connectivity lets you monitor key metrics and remotely power off using the LiTime App. Built with Grade-A LiFePO4 cells, it delivers over 4000 cycles and features an upgraded BMS with 20+ protections, including moisture, dust, and salt spray resistance—ideal for marine trolling motors.
With 1280W of power and 1280Wh of capacity, this battery delivers twice the energy of a standard 100Ah lead-acid battery at only 39% of the weight. Compact, lightweight, and durable, it’s a practical upgrade for those seeking high performance without bulk.
4. LiTime 12V 100Ah Group 31 Trolling Motor Battery
Purpose-built for boating, this 12V 100Ah Group 31 lithium battery is designed to maximize trolling motor performance. Its advanced BMS provides superior protection against moisture, dust, salt spray, and low temperatures, automatically stopping charging below 0°C/32°F and resuming above 5°C/41°F. It also protects against discharging at extreme cold (-20°C/-4°F), reducing the risk of damage.
Engineered with prismatic LiFePO4 cells, it offers excellent thermal stability, low self-discharge, and high power output. Capable of 4000–15,000 cycles and up to 10 years of service life, this battery is a safe, eco-friendly replacement for lead-acid options. With 1280Wh capacity and 1280W output, it also supports 4P4S configurations, enabling the creation of a powerful 51.2V 400Ah battery bank with 20.48kWh of energy—ideal for extended marine power needs.
5. LiTime 12V 140Ah Group 31 Dual Purpose Marine Battery
The LiTime 12V 140Ah Dual Purpose Marine Battery delivers both cranking and deep-cycle power, making it a versatile solution for marine applications. With 1000 CCA, it ensures reliable engine starts even in cold weather, while its deep cycle performance supports trolling motors, fish finders, and onboard electronics.
Designed to replace the need for separate starting and house batteries, it saves space and weight without sacrificing performance. Built for harsh conditions, it features an IP67-rated waterproof casing, a robust BMS, and Bluetooth 5.0 connectivity for real-time monitoring on your phone. Durable, powerful, and compact, this dual-purpose battery is tailored for serious boating needs.
Explore more in the LiTime 12V Battery Series for a full range of Group 31 and Group 24 options. If you need a more compact solution, LiTime’s Group 24 batteries deliver the same high capacity in a smaller footprint—ideal for tight spaces.
FAQs About Group 31 Batteries
1. What are the dimensions of a Group 31 battery?
Group 31 batteries follow the BCI (Battery Council International) standard size, typically measuring 13" L × 6.8" W × 9.4" H (about 330 × 173 × 240 mm).
Pro Tip: While these dimensions are standard, always double-check the specifications of the exact model you’re considering, as minor variations may exist between manufacturers.
2. What is the difference between Group 31 and 8D batteries?
The main differences come down to size, weight, and capacity.
Group 31: A versatile heavy-duty battery, usually weighing 60–75 lbs with a capacity of 75–125Ah (lead-acid). It’s commonly used in semi-trucks, RVs, and marine applications.
Group 8D: Much larger and heavier—typically over 130 lbs with 225–260Ah capacity. These are ideal for extreme, high-demand uses like large off-grid solar systems and industrial equipment.
In short: Group 31 = mobile power, Group 8D = maximum stationary capacity. For a full breakdown, check out our Guide to Group 8D Batteries.
3. Is Group 31 better than Group 24?
Neither is strictly “better”—they’re designed for different needs.
Choose Group 31 if you need higher capacity and longer runtimes for heavy-duty applications, such as powering larger electronics or going longer between charges.
Choose Group 24 when space and weight matter most. It’s smaller, lighter, and works well for compact RVs, smaller boats, or essential backup systems.
For a detailed side-by-side comparison, see our Group 24 vs. Group 31 Guide.
Conclusion
The world of Group 31 batteries extends well beyond traditional lead-acid options. While Flooded Lead-Acid and AGM remain cost-effective choices, the shift is clearly toward Lithium (LiFePO4). Lithium batteries offer longer lifespans, far less weight, zero maintenance, and more usable energy in the same footprint—making them a smarter long-term investment.
Ultimately, the best Group 31 battery is the one that fits your unique balance of power needs, longevity, and budget. By weighing the advantages of each type, you can confidently choose a reliable energy source to keep your equipment running strong for years.
LiTime Team
The LiTime Team is dedicated to bringing you the latest updates, customer stories, and behind-the-scenes insights from the world of LiTime.
