The number “31” on a car battery refers to its group size, a standardized classification by the Battery Council International (BCI) that ensures compatibility with specific vehicles. Group 31 batteries are large, heavy-duty power sources designed for trucks, RVs, and marine applications, offering high cold-cranking amps (CCA) and reserve capacity for demanding electrical systems.
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What Is Battery Group Size 31?
Battery Group Size 31 denotes physical dimensions (typically 13×6.8×9.4 inches) and terminal configuration (top-mounted, SAE posts). This group size ensures the battery fits securely in trays designed for commercial vehicles, off-grid solar systems, or marine equipment. Its standardized design prevents installation errors and optimizes performance in high-vibration environments.
How Does Group 31 Differ From Other Battery Sizes?
Compared to smaller groups like 24 or 34, Group 31 batteries provide 20-30% more capacity (100-125 Ah) and 800-1,000 CCA. They use thicker lead plates and reinforced casings to withstand deep cycling in dual-battery setups or renewable energy storage, unlike starter-focused batteries that prioritize short bursts of power.
Top 5 best-selling Group 14 batteries under $100
| Product Name | Short Description | Amazon URL |
|---|---|---|
|
Weize YTX14 BS ATV Battery  |
Maintenance-free sealed AGM battery, compatible with various motorcycles and powersports vehicles. | View on Amazon |
|
UPLUS ATV Battery YTX14AH-BS  |
Sealed AGM battery designed for ATVs, UTVs, and motorcycles, offering reliable performance. | View on Amazon |
|
Weize YTX20L-BS High Performance  |
High-performance sealed AGM battery suitable for motorcycles and snowmobiles. | View on Amazon |
|
Mighty Max Battery ML-U1-CCAHR  |
Rechargeable SLA AGM battery with 320 CCA, ideal for various powersport applications. | View on Amazon |
|
Battanux 12N9-BS Motorcycle Battery  |
Sealed SLA/AGM battery for ATVs and motorcycles, maintenance-free with advanced technology. | View on Amazon |
| Group Size | Dimensions (inches) | CCA Range | Common Applications |
|---|---|---|---|
| 24 | 10.3×6.8×8.9 | 600-800 | Compact cars |
| 31 | 13×6.8×9.4 | 800-1,000 | Commercial trucks |
| 34 | 10.3×6.8×7.9 | 500-800 | Mid-size SUVs |
Which Vehicles Use Group 31 Batteries?
Group 31 batteries power diesel trucks (Ford F-350, Ram 2500), military vehicles, marine vessels, and RVs. They’re ideal for applications requiring sustained energy output, such as winches, refrigeration units, or inverters. Some off-road enthusiasts upgrade to Group 31 for auxiliary lighting or aftermarket electronics.
Commercial fleets often rely on Group 31 batteries for extended idle times during cargo refrigeration or hydraulic operations. Agricultural equipment like tractors and combines benefit from their vibration resistance in rough terrain. Modern RVs with solar charging systems frequently use paired Group 31 batteries to store 200+ Ah for off-grid camping. Marine applications include powering fish finders, trolling motors, and onboard navigation systems through multi-day fishing trips without shore power.
How to Recycle a Group 31 Battery Safely?
Return spent Group 31 batteries to retailers (AutoZone, Interstate Batteries) under core charge programs. Recycling recovers 99% of lead and plastic. Never landfill—lead exposure risks $10,000+ EPA fines. For lithium batteries, use certified e-waste handlers due to thermal runaway risks during disassembly.
Recycling centers use specialized crushers to separate lead plates from polypropylene casings. The recovered lead gets purified and reused in new batteries, while the plastic is pelletized for manufacturing battery trays. Many states mandate retailers accept up to three batteries per customer monthly. Always transport batteries upright in sealed containers to prevent acid leaks. Some recyclers offer pickup services for commercial quantities exceeding 10 units.
“Group 31’s dominance in commercial sectors stems from its 20% higher plate surface area versus Group 27. This allows sustained 25A draws without voltage sag—critical for hydraulic lifts or emergency lighting. However, users must match alternator output; undercharging causes sulfation in lead-acid types.”
— John Michaels, Senior Engineer at PowerTech Batteries
FAQs
- Can I Use a Group 31 Battery in My Car?
- Only if your vehicle’s tray accommodates 13-inch length batteries. Most passenger cars use smaller groups (35, 51R). Consult your owner’s manual—incorrect sizing may void warranties.
- How Long Do Group 31 Batteries Last?
- Flooded: 3-5 years. AGM: 4-7 years. Lithium: 8-12 years. Lifespan depends on discharge depth—avoid draining below 50% for lead-acid, 20% for lithium.
- Are All Group 31 Batteries Deep Cycle?
- No—some are dual-purpose (starting/cycling). Look for “deep cycle” labels and RC over 180 minutes for true deep-cycle performance.
The “31” on a battery signifies its BCI group size, optimized for heavy-duty applications requiring robust capacity and vibration resistance. When selecting one, prioritize CCA, reserve capacity, and chemistry aligned with your use case—whether it’s diesel cold starts or renewable energy storage. Always verify terminal types and dimensions before purchase.