What size is a group 31 battery?

A Group 31 battery typically measures 13 x 6.8 x 9.4 inches (LxWxH) and weighs 60-80 lbs. It is a heavy-duty battery designed for high-cranking power and deep-cycle applications, commonly used in marine, RV, commercial vehicles, and renewable energy systems. Its large capacity (75-125 Ah) supports sustained power delivery in demanding environments.

What Is a Group Size 24 Battery?

How Do Group 31 Battery Dimensions Compare to Other Battery Groups?

Group 31 batteries are larger than Group 24 (10.25 x 6.8 x 8.9 inches) and Group 27 (12.4 x 6.8 x 9.2 inches) but smaller than Group 8D (20.75 x 8.75 x 9.8 inches). Their balanced size-to-capacity ratio makes them ideal for applications requiring robust power without excessive bulk, such as off-grid solar setups or dual-engine boats.

The physical dimensions of a Group 31 battery directly influence its installation flexibility. For example, in marine applications, the 13-inch length allows secure mounting in standard battery compartments designed for dual-engine configurations. In contrast, smaller Group 24 batteries may require spacer kits to prevent shifting. Commercial truck operators often prefer Group 31 over larger 8D batteries due to easier handling and compatibility with existing battery trays. The 9.4-inch height is critical for clearance in RV underfloor storage compartments, where taller batteries could interfere with plumbing or electrical systems.

Battery Group	Length (inches)	Common Applications
Group 24	10.25	Passenger vehicles, small boats
Group 31	13	Commercial trucks, solar arrays
Group 8D	20.75	Industrial machinery, backup generators

What Maintenance Practices Extend a Group 31 Battery’s Lifespan?

For flooded batteries, monthly electrolyte checks and terminal cleaning prevent sulfation. AGM and lithium-ion types require voltage monitoring (12.6-12.8V resting) and avoiding discharges below 50%. Storage in climate-controlled environments reduces capacity loss, while periodic load testing identifies degradation before failure.

Maintenance routines vary significantly by battery chemistry. Flooded lead-acid models demand distilled water refills to maintain electrolyte levels above lead plates, particularly in high-temperature environments where evaporation accelerates. AGM batteries benefit from quarterly equalization charges at 15.5-15.8 volts to balance cell voltages, a process that should never be attempted on lithium-ion units. Lithium batteries require specialized battery management systems (BMS) to monitor individual cell temperatures and prevent thermal runaway. All types need terminal protection with anti-corrosion gel, especially in saltwater marine applications where oxidation can increase resistance by 40% within six months.

Maintenance Task	Flooded	AGM	Lithium
Water refills	Monthly	Not required	Not required
Voltage checks	Bi-weekly	Monthly	BMS automated
Load testing	Every 6 months	Annually	Every 2 years

“Group 31’s dominance in marine and renewable sectors stems from its adaptability. Lithium variants now offer 3,000+ cycles at 100% DoD, slashing long-term costs. However, proper busbar sizing and temperature-compensated charging remain critical—oversights here cause 70% of premature failures we see.” — Senior Engineer, Global Battery Solutions

FAQs

Can a Group 31 Battery Fit in a Group 27 Tray?

No—Group 31’s 13-inch length exceeds Group 27 trays. Retrofitting requires modifying tray dimensions and securing brackets to prevent vibration damage.

Are Group 31 Batteries Interchangeable Between Marine and Automotive Uses?

Marine Group 31 batteries (dual-purpose CCA/RC) can replace automotive ones, but automotive batteries lack the deep-cycle endurance needed for marine accessories.

What Is the Typical Lifespan of a Group 31 AGM Battery?

4-7 years with proper charging (13.8-14.7V) and avoiding discharges below 10.5V. Temperature extremes or chronic undercharging reduce lifespan by 30-50%.