“Group 31” is a standardized battery size code that refers to the case’s external dimensions and terminal layout. It doesn’t specify chemistry or performance. On this page, you’ll see 12V Group 31 batteries in different chemistries (like AGM and lithium) and for different roles (starting or deep cycle).

• What it covers: Physical size/footprint and where the terminals are located.
• What it doesn’t: Capacity, cranking amps, or internal design—those vary by model.

To choose confidently, match the group size your tray or compartment is built for, then compare specs such as cranking amps, amp‑hours, reserve capacity, and intended use. Your owner’s manual and Walmart.com filters can help you confirm the right fit and performance.

Both are standard size codes. In general, Group 31 batteries are larger than Group 27, which can allow for more capacity or higher cranking performance, depending on the design and chemistry.

• Fitment: Group 31 takes more space. Always measure your tray and check hold‑downs and height clearance.
• Capacity potential: Group 31 often comes in higher amp‑hour deep‑cycle options, but exact ratings vary by model.
• Weight: Larger cases can be heavier (especially in lead‑acid), while lithium options are lighter for the same size.
• Terminals: Post type and orientation can differ—confirm layout before buying.

If your compartment is set up for Group 27, a Group 31 may not fit without changes. Verify dimensions and specs on Walmart.com before purchasing.

Group 31 batteries are popular where robust power and durability are needed. You’ll commonly see them in:

• Heavy‑duty trucks and commercial equipment for starting power.
• RVs and travel trailers as chassis or house batteries.
• Marine setups for engine starting or trolling motors (when sized appropriately).
• Off‑grid and solar energy storage banks.
• Specialty power needs like audio systems or backup power.

Use your vehicle or equipment manual to confirm group size, terminal layout, and performance needs (e.g., cranking amps for starting or amp‑hours for deep‑cycle use). On Walmart.com, filters let you narrow by group size, chemistry, and application, with pickup or delivery available in many areas.

Pick based on fit, power needs, and charging setup rather than a single “best” size.

• Fitment: Group 24 is smaller, Group 31 is larger. Confirm tray size, hold‑downs, and terminal orientation.
• Use case: For engine starting, match required cranking amps. For house/trolling loads, compare amp‑hours and reserve capacity within the correct group.
• Weight/handling: Larger cases may be heavier; plan for safe installation and service.
• Charging: Ensure your charger or alternator settings align with the battery’s chemistry and capacity.

When uncertain, stick with the group size specified by your manufacturer and then compare specs within that size. Walmart’s site tools help you filter by chemistry, application, and features.

Upgrading from lead‑acid to a lithium iron phosphate (LiFePO4) Group 31 can reduce weight and increase usable capacity, but a few checks help things go smoothly.

• Fit & mounts: Group 31 cases are standardized, but verify overall height and hold‑downs.
• Charging profile: Use a charger compatible with LiFePO4. Some systems may need setting changes or a DC‑DC charger in RV/boat setups.
• Temperature: Many lithium models include low‑temperature cut‑off; avoid charging below the stated range unless supported.
• BMS ratings: Built‑in protection helps, but confirm the battery’s continuous/peak current matches your inverter, motor, or loads.

Review product specs and your system requirements on Walmart.com to ensure compatibility.