Group 31 batteries are heavy-duty, high-capacity power sources designed for applications requiring robust performance and extended runtime. With dimensions around 13×6.8×9.4 inches, they offer 75–125 Ah capacity, 800–1000 CCA, and 160–220 minute reserve capacity (RC). Ideal for commercial trucks, marine systems, and solar storage, they utilize AGM or lithium-ion technology for vibration resistance and deep-cycle durability. Pro Tip: Pair with a compatible smart charger to prevent under/overcharging.
What Is the Best Lithium Battery for RV Use?
What defines a Group 31 battery?
A Group 31 battery is characterized by its large case size (13″ L x 6.8″ W x 9.4″ H) and high reserve capacity (160–220 minutes). Designed for deep-cycle use, it withstands repeated discharges down to 50% depth of discharge (DoD), outperforming smaller groups in commercial and marine environments. Lithium variants reduce weight by 40% versus lead-acid.
Group 31 batteries prioritize capacity over compactness, making them the go-to choice for energy-hungry systems. Their terminal design typically uses M8 studs for secure connections in high-vibration settings like heavy trucks. AGM versions excel in marine applications due to spill-proof construction, while lithium models offer 3,000–5,000 cycles at 100% DoD. For example, a 100Ah lithium Group 31 battery can power a 1,000W inverter for 1+ hour. Pro Tip: Always check terminal orientation—some Group 31 batteries use reverse polarity. But what if you need more power? Series connections can boost voltage, but parallel setups require identical batteries to prevent imbalance.
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 |
| Parameter | Group 31 | Group 27 |
|---|---|---|
| Capacity (Ah) | 75–125 | 65–100 |
| CCA | 800–1000 | 600–800 |
| Weight (lbs) | 60–80 (AGM) | 50–60 (AGM) |
Why choose Group 31 over smaller battery groups?
Group 31 batteries provide 40% more runtime than Group 27 in similar applications, thanks to higher Ah ratings. Their thicker plates endure deeper discharges, making them superior for trolling motors or off-grid solar setups where daily cycling occurs.
When considering power needs, Group 31’s advantage lies in sustained output. A 125Ah model supports 150A continuous draw vs. Group 24’s 100A limit. They’re also built tougher—AGM variants handle 2x the vibration of flooded batteries. For RVers, this means reliable power for air conditioners and appliances during boondocking. Practically speaking, upgrading from Group 24 to 31 in a marine system can extend trolling motor runtime from 6 to 9 hours. Warning: Verify your battery tray size—Group 31 requires 30% more space than Group 24.
Are Group 31 batteries suitable for marine use?
Yes—marine-grade Group 31 batteries feature AGM sealing to prevent acid spills and corrosion-resistant terminals. Their deep-cycle design handles the constant charge/discharge cycles of fish finders and bilge pumps, outperforming starting batteries in dual-purpose roles.
In saltwater environments, Group 31’s robust construction shines. A 31M (marine) battery typically has 210 minutes RC—enough to anchor a boat overnight while powering navigation lights and radios. Lithium models add advantages: they charge 2x faster than AGM and aren’t damaged by partial charging. For example, Dakota Lithium’s 125Ah Group 31 weighs just 31 lbs versus 75 lbs for AGM, critical for hull balance. Pro Tip: Use marine-specific battery boxes even with AGM to protect against splash damage. Did you know? Some Group 31 marine batteries include built-in handles for easier installation in tight engine compartments.
| Feature | AGM Group 31 | Lithium Group 31 |
|---|---|---|
| Cycle Life | 500–800 | 3,000–5,000 |
| Weight | 60–80 lbs | 25–35 lbs |
| Charge Time | 8–10 hours | 3–5 hours |
How long do Group 31 batteries last?
Lifespan varies by chemistry: AGM lasts 4–6 years with proper maintenance, while lithium models reach 8–12 years. Cycles range from 500–800 (AGM) to 3,000–5,000 (LiFePO4) at 80% DoD. Temperature and charging habits critically impact longevity.
Beyond chemistry, installation practices matter. A Group 31 battery in a ventilated compartment at 77°F lasts 20% longer than one exposed to 95°F heat. Regular equalization charges help AGM units avoid sulfation, but lithium batteries don’t require this. For solar setups, adding a battery heater ($50–$100) prevents lithium capacity loss below freezing. Real-world example: A well-maintained AGM Group 31 in a food truck delivers 5+ years of daily 50% discharges. Pro Tip: Monitor voltage monthly—12.6V means 75% charge in AGM; 13.3V indicates full charge in lithium.
What charging systems work best for Group 31?
Smart multi-stage chargers with temperature compensation are ideal. AGM needs 14.4–14.8V absorption; lithium requires 14.6V. Chargers should deliver 10–30% of battery capacity (e.g., 25A for 100Ah). Solar systems need MPPT controllers to handle high current safely.
Charging a Group 31 battery isn’t one-size-fits-all. AGM models demand precise voltage control—overcharging above 15V causes gassing, while undercharging below 12.4V leads to sulfation. Lithium’s BMS handles overvoltage, but chargers must match the chemistry. For marine dual-bank systems, consider a 40A charger like NOCO Genius 40 to replenish two 100Ah batteries overnight. Did you know? Using a car alternator to charge lithium Group 31 batteries requires a DC-DC charger to prevent overloading the alternator.
Are Group 31 batteries cost-effective?
Initially pricier than smaller groups, Group 31 offers lower cost per cycle—$0.10/cycle for lithium vs. $0.30 for AGM. Their extended lifespan and reduced replacement frequency justify upfront costs in commercial/off-grid use.
When calculating ROI, consider energy throughput. A $900 lithium Group 31 delivering 5,000 cycles at 100Ah provides 500,000 Ah total—$0.0018/Ah. Comparatively, a $300 AGM unit offering 800 cycles yields 80,000 Ah at $0.00375/Ah. For a fishing charter boat running daily, this difference saves $1,200+ over 5 years. Pro Tip: Negotiate bulk pricing when buying multiple units for fleet vehicles. But what about occasional users? For weekend RVers, a cheaper AGM may suffice unless weight savings are critical.
Battery Expert Insight
FAQs
No—measure your battery tray first. Group 31 requires ~13″L x 6.8″W. Many trucks/RVs have compatible trays, but sedans usually don’t.
Do lithium Group 31 need special maintenance?
Minimal—no watering or equalization. However, store at 50% charge if inactive for 3+ months to prevent BMS drain.