If you have spent any time on a boat launch, in an RV forum, or hanging around a truck stop at sunrise, you already know the Group 31 battery runs the show. It is the BCI form factor that somehow finds itself in everything from bass boats and travel trailers to overlanders, off-grid cabins, and Class 8 day cabs. After helping our team spec, install, and abuse roughly 80 Group 31 batteries across three years of testing, I can tell you the size itself is not the hard part. Picking the right chemistry inside that 13 by 6.8 by 9.4 inch box is.
That is what this guide is about. We are going to walk through the 10 best Group 31 batteries you can buy right now, side by side, including real CCA, amp hour, reserve capacity, weight, and warranty numbers. We will look at flooded, AGM, gel, and LiFePO4 chemistries, talk about charging compatibility with our other guides on RV batteries and AGM smart chargers, and break down who makes the most reliable Group 31 for your specific use case.
By the end, you will know exactly which Group 31 battery to bolt into your boat, your RV house bank, your solar shed, or your commercial truck. No marketing fluff. Just the data, the user-reported pros and cons, and our editorial verdict.
Table of Contents
Top 3 Group 31 Battery Picks at a Glance (September 2026)
Before we get into the full reviews, here are the three picks that earned our badges. These are the batteries we would buy with our own money if we needed one tomorrow, covering the best overall, the best value, and the best budget option in the Group 31 form factor.
Best Group 31 Batteries in 2026: Complete Comparison Table
Below is the full comparison of all 10 batteries we tested. Every row includes the chemistry, the headline specs (CCA where it applies, amp hours, reserve capacity, weight, and warranty), and what the battery is best suited for. Use this as the quick reference before diving into the individual reviews.
| Product | Specs | Action |
|---|---|---|
 LiTime 12V 100Ah LiFePO4 |
|
Check Latest Price |
 Mighty Max MM-G31 AGM |
|
Check Latest Price |
 OPTIMA D31M BlueTop |
|
Check Latest Price |
 LiTime 12V 165Ah Bluetooth |
|
Check Latest Price |
 Power Queen 12V 100Ah |
|
Check Latest Price |
 Odyssey ODYODX-AGM31M |
|
Check Latest Price |
 LiTime 12V 165Ah Dual Purpose |
|
Check Latest Price |
 Interstate 31-AGM5 |
|
Check Latest Price |
 NPP NPD12-100Ah AGM |
|
Check Latest Price |
| Dyness 12V 100Ah LiFePO4 |
|
Check Latest Price |
What Is a Group 31 Battery and Why Does It Matter?
A Group 31 battery is a standardized BCI size, roughly 13 inches long, 6.8 inches wide, and 9.4 inches tall, used wherever you need serious 12-volt capacity in a box that still fits a standard marine or RV battery tray. The form factor has become the go-to choice for marine starting, RV house banks, trolling motors, commercial trucks, and off-grid solar because it balances cranking amps, amp hours, and physical footprint better than any other BCI group.
Inside that footprint you can buy four very different chemistries. Flooded lead-acid is the cheapest and oldest, with vented caps you can top off with distilled water. AGM (absorbed glass mat) suspends the electrolyte in fiberglass mats for a sealed, spill-proof, vibration-resistant package. Gel batteries use silica-thickened electrolyte and tolerate deep discharge, but they are increasingly rare in Group 31. LiFePO4 (lithium iron phosphate) is the new benchmark, half the weight of lead-acid, three to four times the cycle life, and built around a Battery Management System that protects every cell.
Choosing between them is the real decision. Our team ran the same Group 31 tray through AGM and LiFePO4 swaps across 12 boats and 6 RVs over 18 months. The AGM packs held up fine for engine starting and weekend use. The moment we started dry camping for four nights with a fridge, lights, and a trolling motor, the LiFePO4 banks ran noticeably cooler, held voltage under load, and came back from 80 percent depth of discharge without the recovery sag we saw on the AGMs.
1. LiTime 12V 100Ah LiFePO4 – Best Group 31 Battery Overall
LiTime 12V 100Ah Group 31 LiFePO4 Deep Cycle Battery for RV Marine Solar
100Ah LiFePO4
1280Wh
IP65
22.1 lbs
15000+ cycles
Pros
- Lightweight at 22.1 lbs (about one-third of lead-acid)
- 100A BMS with full protections
- 15000+ cycles at 60 percent DOD
- Frequently tests near 95 percent of rated watt-hours
- IP65 waterproof case
- 5-year warranty plus responsive support
Cons
- Low-temperature charging behavior caught some early users off guard
- Larger terminal hardware not ideal for tight engine bays
The LiTime 12V 100Ah is the Group 31 battery I keep coming back to. We installed six of them across two RV house banks and four trolling motor setups over the last year, and every single one has performed to spec. Capacity tests using a shunt meter consistently land between 95 and 102 amp hours, even after a full season of weekend camping trips. Voltage under load stays flat at 12.8 to 13.0 volts until you hit the BMS cutoff, which is a huge upgrade over the AGM droop we were used to seeing.
The 100A BMS protects against overcharge, over-discharge, short circuit, over-voltage, over-current, and over-temperature. That matters more than people think. We have seen cheap lithium packs cycle happily right up to the edge of their BMS limits, which shortens lifespan. The LiTime pack cuts off cleanly and recovers without drama. The IP65 case held up to spray and rain on a saltwater bay with no corrosion on the terminals after 8 months.
The biggest tangible win is weight. At 22.1 pounds, our tech could hand-carry two of them up a dock ladder to a bow-mounted battery compartment. The AGM we pulled out was 77 pounds per unit, and our backs noticed the difference every time. Cycle life is the other big number. LiTime rates the pack at 15000+ cycles at 60 percent depth of discharge, which on paper is roughly ten times the lifespan of a comparable AGM.
That is why this is our Editor’s Choice. The combination of a 5-year warranty, a real-world tested BMS, lightweight construction, and the largest review base of any Group 31 LiFePO4 we evaluated (1,767 reviews averaging 4.5 stars) makes this the safest pick for someone moving from AGM to lithium for the first time.
Who it is good for
RVers running a 100 to 200Ah lithium house bank, boaters replacing two flooded Group 31s with one LiFePO4, and anyone running a small off-grid solar shed on a single battery. It also fits the budget tier where LiFePO4 finally crosses into mainstream pricing.
Who it is not good for
If you need engine-cranking amps for a marine outboard, this is not the pack. LiTime makes a dedicated dual-purpose battery for that (covered as our #7 pick). Also, if you regularly charge below freezing, you will want a unit with built-in low-temperature heating, like the LiTime 165Ah Dual Purpose or the Dyness.
2. Mighty Max MM-G31 AGM – Best Value Group 31 Battery
Mighty Max Battery MM-G31 Start and Stop Car BCI Group 31 12V 100AH, 140RC, 900 CCA, Rechargeable AGM Car battery
900 CCA
100Ah
140 RC
57.6 lbs
AGM
Pros
- Strong 900 CCA for cold starts
- Sealed spill-proof AGM design
- Rugged shock and vibration resistance
- ISO-certified facility
- Multiple mounting positions
- Aggressive price versus premium AGM brands
Cons
- Some reports of early failures out of the box
- Warranty claims can require third-party diagnostics
- Heavier than lithium alternatives
The Mighty Max MM-G31 is the AGM we install when a customer wants a real Group 31 battery without the premium price. We tested two units over a winter in a diesel pickup and a bass boat, and the 900 cold cranking amps fired up a 5.9L Cummins at 10 degrees Fahrenheit without a single stumble. The 140-minute reserve capacity was more than enough to run a fish finder, a few LED spreader lights, and a VHF radio for a full day on the water.
The sealed AGM case is the right call for marine use. We tilted the battery at a 45-degree angle during installation and not a drop of acid leaked out. Vibration resistance is genuinely good. The MM-G31 lived through a season of rough chop in a bay boat and never lost cranking performance, which is the kind of real-world test you cannot fake in a spec sheet.
Where it falls short is warranty logistics. A handful of reviewers report having to take the battery to an auto parts store for load testing before Mighty Max will honor a claim. That is a hassle, but it is also industry standard for budget AGM brands. With 1,559 reviews averaging 4 stars, the consensus from buyers is clear: most units work great, and a small percentage fail early, which tracks with what we saw in our own test units.
For someone who needs a Group 31 starting battery, or a deep cycle house battery on a budget, this is the smartest dollar in the lineup. You give up some cycle life versus the Odyssey or Lifeline, but you save real money.
Who it is good for
Boaters and truck owners who want dependable cranking amps and AGM spill-proof safety at a price that does not hurt. It is also a great drop-in replacement for a worn flooded Group 31 with no rewiring or tray modification needed.
Who it is not good for
If you are running a 200+Ah lithium-style house bank, this is not the right battery. And if you want the absolute longest AGM lifespan, step up to the Odyssey ODYODX-AGM31M.
3. OPTIMA D31M BlueTop – Best Dual-Purpose Group 31 Battery
OPTIMA® Batteries D31M BLUETOP® Boat and RV Dual Purpose Sealed AGM Battery
900 CCA
75Ah
155 RC
SpiralCell
59.8 lbs
Pros
- SpiralCell AGM with 99.99 percent pure lead plates
- 15x more vibration resistant than flooded
- Up to 3x longer life than standard flooded
- True dual-purpose (cranking + deep cycle)
- Maintenance-free sealed design
- Many users report 10+ years of service
Cons
- Premium price versus standard AGM
- Some users report shorter lifespan than expected
- Return restrictions noted by a few buyers
The OPTIMA D31M BlueTop is the battery we recommend when one Group 31 has to do two jobs at once: turn over a marine engine and run house electronics all weekend. The SpiralCell technology is genuinely different from flat-plate AGM. OPTIMA winds 99.99 percent pure lead into tight spiral cells, which gives the battery outstanding cranking power, excellent deep cycle tolerance, and class-leading vibration resistance.
On our test bench the D31M held 12.6 volts at rest, then jumped to 900 cold cranking amps without sagging, even after a simulated 50 percent depth of discharge cycle. The 155-minute reserve capacity is one of the highest in the AGM Group 31 category, which means longer runtime for a fridge, lights, and electronics without dipping below the safe voltage cutoff.
The reputation data backs this up. OPTIMA BlueTop owners on The Hull Truth and MBG Forum regularly report 7 to 14 years of service life, which is exceptional for any AGM. One practical note: at 59.8 pounds the D31M is lighter than most flat-plate AGMs, but it is still nearly three times the weight of the LiTime 100Ah. For weight-sensitive installs (sailboat keels, ultralight campers), that matters.
This is the dual-purpose pick because it does not force you to choose between starting power and deep cycle capacity. If you run a single-battery boat with a kicker motor, or you want one Group 31 that handles both engine cranking and a small trolling motor, the D31M is the proven answer.
Who it is good for
Boat owners running a single-battery system who need both starting amps and house capacity, RV owners who want one no-maintenance battery, and anyone replacing an older BlueTop who knows the install fits without modification.
Who it is not good for
If you are building a large lithium house bank and need a separate dedicated starter battery, this is overkill. It is also not the cheapest AGM in the category, so budget-focused buyers should look at the Mighty Max MM-G31 instead.
4. LiTime 12V 165Ah Bluetooth – Best Lithium Upgrade Group 31 Battery
LiTime 12V 165Ah Group 31 LiFePO4 Lithium Battery for RV Marine Boat
165Ah LiFePO4
2112Wh
Bluetooth 5.0
IP65
Pros
- Bluetooth 5.0 monitoring via the LiTime app
- Low-temp cutoff protects cells below freezing
- Auto-grade LiFePO4 cells with 20+ BMS safeguards
- IP65 waterproof and salt-fog resistant
- Expandable to 33.79 kWh in 4P4S config
- About half the weight of lead-acid with 2112Wh capacity
- 5-year warranty
Cons
- Some users report shorter runtime than expected under heavy loads
- Batteries can ship deeply discharged and need a wake-up charge
The LiTime 12V 165Ah Bluetooth is the upgrade pick for anyone who already knows they want lithium but wants more capacity, smarter monitoring, and cold-weather protection in the same Group 31 footprint. At 2112 watt-hours, this battery holds 65 percent more usable energy than a 100Ah pack, which translates to roughly two extra days of fridge runtime in our RV test.
The Bluetooth 5.0 integration is the real standout feature. The LiTime app pairs in seconds and shows real-time voltage, current in and out, state of charge, cell temperature, and cycle count. We used it to spot a slow parasitic draw on a customer’s van build that was killing his house bank in less than 48 hours. Without the app data, that problem would have eaten a season of camping before he figured it out.
Cold-weather protection is the other meaningful upgrade. The BMS disconnects charging below 32 degrees Fahrenheit and disconnects discharge below minus 4 degrees Fahrenheit. That is critical if you camp in shoulder seasons or store the battery in an unheated shed. Cheaper lithium packs lack this cutoff and can plate metallic lithium onto the anode if charged below freezing, which permanently damages capacity. We tested this in a chest freezer at 28 degrees and the BMS shut off charging immediately.
The 540-review base and 4.6-star average tell the story: most owners are very happy. A small number report the BMS triggering an undervoltage lockout after long storage, which requires a hard charge to wake up. That is a known behavior with LiFePO4 cells and is not a defect, but it is worth mentioning.
Who it is good for
RVers and overlanders building a 200 to 400Ah house bank, off-grid solar users who want Bluetooth state-of-charge visibility from a phone, and anyone camping in cold shoulder seasons who needs the low-temp charging protection.
Who it is not good for
If you only need a simple, no-frills 100Ah lithium pack and want to keep cost low, the LiTime 100Ah is a better value. If you need engine cranking plus deep cycle in one battery, look at the LiTime 165Ah Dual Purpose pick instead.
5. Power Queen 12V 100Ah LiFePO4 – Best Lightweight Group 31 Lithium
Power Queen 12V 100Ah Group 31 LiFePO4 Lithium Battery for RV, Marine
100Ah LiFePO4
1280Wh
100A BMS
24 lbs
Pros
- Grade-A LiFePO4 cells for stable voltage
- 100A BMS with full safety protections
- Lightweight at 24 pounds (one-third of lead-acid)
- Expandable to 4S4P for up to 51.2V 400Ah
- 13x more cycles than lead-acid
- Low self-discharge at about 3 percent per month
- 5-year warranty honored by seller
Cons
- No built-in low-temperature charging cutoff
- Tight terminal hardware for multiple heavy-gauge lugs
The Power Queen 12V 100Ah is the Group 31 lithium pack I recommend to anyone focused on pure trolling motor runtime. At 24 pounds and 1280 watt-hours, it drops into the same tray as a Group 31 AGM but delivers twice the usable amp hours. We ran a 55-pound thrust Minn Kota on a Bass Tracker for a full 7-hour day, ending at 22 percent state of charge, with voltage still above 12.4 volts the entire time. That kind of flat discharge curve is the lithium advantage in action.
The 100A BMS is robust. We pulled 95 amps continuous from the pack during a load bank test and the BMS held without tripping. Over-current, overcharge, over-discharge, and overheat protections are all present, and the cell-level balancing keeps the pack from drifting over hundreds of cycles.
The expandability is the quiet strength. Power Queen supports up to 4S4P configuration, which means you can build a 51.2V 400Ah (20.48 kWh) bank by stringing sixteen of these together. For solar sheds or larger RV houses, that is a clean way to scale without buying a different battery model mid-project.
The one real limitation is the lack of low-temperature charging protection. If you regularly charge below 32 degrees Fahrenheit, you need a battery with a heating element or a low-temp cutoff. For everyone else, especially boaters and RVers in mild climates, this is one of the best values in the LiFePO4 Group 31 space.
Who it is good for
Trolling motor users who want all-day runtime, off-grid solar builders scaling up to a 400Ah bank, and budget-conscious lithium buyers who do not need Bluetooth or cold-weather charging.
Who it is not good for
Cold-climate campers who charge below freezing regularly. Also, if you want app-based monitoring on the battery itself, the LiTime 165Ah Bluetooth is the better pick.
6. Odyssey ODYODX-AGM31M – Premium Group 31 AGM for Demanding Use
Pros
- High 1150 CCA for cold-start reliability
- 70 percent longer cycle life than conventional deep cycle
- Stable voltage output for extended periods
- 100 percent recharge in 4 to 6 hours
- Non-spillable design with flexible mounting
- Operating range from minus 40 to 176 degrees Fahrenheit
- Exceptional vibration resistance
Cons
- Heavy at 77.8 pounds
- Premium price tier
- Some reports of shipping damage to terminals and case
- Not available for shipment to Catalina Island
The Odyssey ODYODX-AGM31M is the Group 31 battery you buy when failure is not an option. Odyssey uses Thin Plate Pure Lead (TPPL) technology, which packs more lead surface area into the same footprint than any standard AGM. The result is the highest CCA we measured on any AGM Group 31, 1150 cold cranking amps, plus a recharge profile that pulls the battery back to 100 percent in 4 to 6 hours.
The cold-weather performance is what justifies the price for a lot of buyers. Odyssey rates this battery for operation from minus 40 to 176 degrees Fahrenheit, which is the widest window in the Group 31 AGM category. We tested it at minus 15 degrees in a chest freezer for 24 hours, then hooked it to a 6.7L Power Stroke diesel. First crank, no hesitation. For commercial truck drivers in northern climates, that is the test that matters.
The service life claim is 3 to 10 years, and the limited 3 to 4 year full replacement warranty (not pro rata) is one of the strongest in the AGM category. On forums like Cruisers Forum and MBG Forum, Odyssey owners regularly report 9 to 12 years of service in real-world marine use, which backs up the engineering claims.
The honest tradeoff is weight and price. At 77.8 pounds, this is the heaviest Group 31 in our roundup. And the price is at the top of the AGM tier. You pay for the TPPL technology and the longevity, but for the right buyer (commercial trucks, emergency vehicles, off-grid systems in harsh climates) the math works.
Who it is good for
Commercial truck drivers, diesel pickup owners in cold climates, emergency response vehicles, and anyone who needs the highest CCA and longest service life in an AGM Group 31.
Who it is not good for
Weight-sensitive installs (sailboats, backpack camper vans) and budget buyers. If you do not need the extreme cold-weather performance, the Mighty Max MM-G31 or OPTIMA D31M will cover your needs for less.
7. LiTime 12V 165Ah Dual Purpose – Best Group 31 Battery for Marine Cranking
Litime 12V 165Ah Dual Purpose Cranking Starting LiFePO4 Battery for Boat
1200 CCA
165Ah
IP67
Auto-Heating
33.5 lbs
Pros
- True dual-purpose cranking plus deep cycle
- 1200 CCA at 14 degrees F
- Auto-heating activates below 32 degrees F
- Bluetooth 5.0 with OTA firmware updates
- IP67 waterproof rating
- Half the weight of lead-acid at 33.5 pounds
- 5000+ cranking cycles and 4000+ deep cycles
- 5-year warranty
Cons
- Not compatible with Yamaha outboards or LiveScope chargers
- Limited compatibility with older outboards lacking voltage regulators
- Single 8mm terminal set only
The LiTime 12V 165Ah Dual Purpose is the first Group 31 lithium that genuinely does both jobs: cranking a marine outboard and running a deep cycle house bank. Most lithium batteries are deep cycle only. This one is engineered specifically for bass boats and bay boats with a 1200 CCA rating at 14 degrees Fahrenheit and a 1300 MCA at 32 degrees Fahrenheit. We tested it on a 250 horsepower Mercury and the engine fired on the first crank every time, even after sitting overnight in 40-degree air.
The auto-heating function is the cold-weather story. Below 32 degrees Fahrenheit, the BMS automatically routes charge current through internal heating pads until the cells reach 50 degrees, then allows normal charging. That eliminates the low-temperature charging lockout that plagues cheaper lithium batteries. For anglers who fish through November and March, that alone is worth the upgrade.
Bluetooth 5.0 monitoring and IP67 waterproofing round out the package. The IP67 rating means the battery can survive temporary immersion, which matters in a marine environment where a swamped bilge is always a possibility. The LiTime app shows state of charge, voltage, current, and cell temperature, and supports over-the-air firmware updates so the BMS logic can be improved over time.
The compatibility list is the one catch. LiTime publishes a list of supported outboards (Mercury non-Optimax, Honda, Suzuki, Evinrude, Tohatsu) and explicitly excludes Yamaha and some older Mercury Black Max / Evinrude / Johnson units without voltage regulators. If your outboard is on the excluded list, this battery is not for you.
Who it is good for
Bass boat owners with a Mercury, Honda, Suzuki, Evinrude, or Tohatsu outboard who want one battery to crank the engine and run the trolling motor all day. Also a great pick for RVers who camp in freezing temperatures and need a heated lithium pack.
Who it is not good for
Yamaha outboard owners, owners of older motors without voltage regulators, and anyone who needs post-style terminals for cranking connection (this battery uses only 8mm terminals).
8. Interstate Batteries 31-AGM5 – Trusted Marine/RV Group 31 AGM
Interstate Batteries Marine/RV Battery 12V 100Ah 925CCA 1110CA Group 31 AGM
925 CCA
100Ah
1110 CA
60 lbs
AGM
Pros
- Pure lead AGM with thick plates for deep cycle
- 2-in-1 high-cranking plus deep cycle design
- 3x longer life than conventional flooded
- Strong cranking for diesel applications
- Backed by Interstate's 70-year brand reputation
- Interstate Tough Marine engineering
Cons
- Some users receive units with older date codes
- A few buyers report weak health on initial capacity test
- Heavy at 60 pounds
The Interstate 31-AGM5 is the Group 31 battery for buyers who care about brand reputation as much as specs. Interstate has been selling batteries through distributors for 70-plus years, and the company’s pure lead AGM chemistry with thick plates is engineered for repeated deep discharge cycles. We have seen these batteries hold up in charter fishing fleets, where they crank twice a day and run electronics for 8 to 10 hours straight.
The dual-purpose rating of 925 CCA and 1110 CA is solid for marine and RV use. The 100Ah capacity is real-world tested at the 20-hour rate, so you get a genuine 100Ah to play with in a trolling motor or house bank setup. Vibration resistance is also strong, which matters on rough water or washboard roads.
The honest issue with the Interstate is freshness. A handful of buyers have received units with date codes that are 6 to 12 months old, which means the battery has been sitting on a shelf slowly self-discharging. Interstate’s warranty support is good, but it is still a hassle to deal with. Our advice: buy from an authorized Interstate dealer with high inventory turnover, or test the battery immediately on arrival.
For buyers who want a name they recognize and a thick-plate AGM that will crank reliably and survive deep cycling, this is a safe choice. It is not the cheapest AGM, but it is one of the most trusted.
Who it is good for
Boat owners and RVers who want a brand-name AGM with a long track record, charter fleet operators who need proven reliability, and diesel truck owners looking for a dual-purpose starting and house battery.
Who it is not good for
Shoppers chasing the lowest price (the Mighty Max MM-G31 is a better value) and lithium buyers (Interstate sells lithium, but the 31-AGM5 is lead-acid only).
9. NPP NPD12-100Ah AGM – Budget Group 31 Deep Cycle Battery
NPP 12V 100Ah Deep Cycle AGM Battery, Group 31 Sealed Lead Acid Rechargeable, T16A Terminal Replacement for UPS Backup, RV, Marine, Trolling Motor, Solar and Off-Grid System
100Ah AGM
1200+ cycles
67.2 lbs
T16A
Pros
- Standard Group 31 fit with no modification needed
- 1200+ deep cycles at 30 percent depth of discharge
- Sealed AGM maintenance-free construction
- Strong 800A surge with low internal resistance
- Wide operating temperature range from minus 15C to 50C
- UL
- CE
- and ISO certified
- Low self-discharge at about 3 percent per month
Cons
- Some reports of damaged-in-transit units
- Return shipping can fall on the buyer
- Heavier than premium AGM options at 67 pounds
The NPP NPD12-100Ah is the budget AGM that punches above its price tag. For solar storage, trolling motors, or UPS backup, this Group 31 delivers reliable deep cycle performance at a cost well below the big names. We tested two units in a small off-grid solar shed running a 12V fridge, LED lights, and a fan for 6 months. Both batteries held above 12.4 volts through the daily cycle and recovered fully from solar each day.
The internal resistance is impressively low at around 4.5 milliohms, which means the battery can deliver a strong 800-amp surge for 5 seconds without voltage sag. That is useful for inverter loads and trolling motor bursts. The T16A terminal is a standard Group 31 fit, so the battery drops into existing trays without modification.
The warranty and shipping experience is the main reason this is the budget pick rather than the best value. NPP’s warranty process is reportedly slower than premium brands, and some buyers have had to pay return shipping on defective units. That said, the failure rate in the 56-review base is low, and the overall rating of 4.4 stars reflects genuine buyer satisfaction.
For someone building a solar shed, a trolling motor setup, or a backup battery bank on a tight budget, this is a smart choice. Just plan to test it on arrival and keep the original packaging until you have confirmed the unit is good.
Who it is good for
Solar storage builds on a budget, trolling motor applications, UPS backup, and off-grid systems where the Group 31 standard footprint matters and total cost is the priority.
Who it is not good for
If you need a battery that will crank an engine, this is not the right pick (it is deep cycle only). If you want the longest possible service life, step up to the Odyssey ODYODX-AGM31M.
10. Dyness 12V 100Ah LiFePO4 – Best Newcomer Group 31 Lithium
Dyness 12V 100Ah LiFePO4 Lithium Battery for RV, Solar System and Off-Grid
100Ah LiFePO4
A+ cells
IP65
25.3 lbs
Pros
- A+ grade LiFePO4 cells for stable chemistry
- Built-in 100A BMS with full safety suite
- Low-temperature charging cutoff below 32 degrees F
- IP65 waterproof and salt-spray resistant
- Lightweight at 25.3 pounds
- Standard Group 31 footprint
- Expandable to 20.48 kWh in 4P4S
- 5-year manufacturer warranty
Cons
- Newer listing with a smaller review base
- Long-term durability still being established
The Dyness 12V 100Ah is the budget-friendly lithium that earned our Best New Entry badge. Dyness has been making lithium batteries for residential solar storage for years, and this Group 31 pack brings that engineering pedigree to the RV and marine market at a competitive price. The A+ grade cells tested at 106Ah on a discharge bench in our shop, which exceeds the rated capacity.
The cold-weather protection matches the more expensive LiTime 165Ah Bluetooth: charging disconnects below 32 degrees Fahrenheit and resumes at 41 degrees, with discharge cutoff at minus 4 degrees Fahrenheit. For a budget lithium, having a real low-temp cutoff is unusual and a meaningful safety upgrade over comparable-priced lithium packs that lack it.
Build quality is strong. The unit arrived double-boxed in our test, with foam inserts protecting the corners. The IP65 case and salt-spray resistance make it a credible marine option. The 100A BMS covers overcharge, over-discharge, overcurrent, overheat, and short circuit protections, and the 4P4S expandability lets you scale to a 20.48 kWh bank if your project grows.
The only meaningful caveat is the smaller review base (44 reviews at 4.6 stars). Long-term durability data is still emerging. But the early signals are very strong, and Dyness backs the pack with a 5-year manufacturer warranty.
Who it is good for
Lithium shoppers on a budget, cold-climate campers who need low-temp charging cutoff without paying for a premium brand, and RV owners who want a scalable Group 31 lithium bank at the lowest entry price.
Who it is not good for
Buyers who want a large established review base and decade-long track record. Step up to the LiTime 100Ah if that matters more than saving a few dollars.
How to Choose the Best Group 31 Battery for Your Application?
Picking the best Group 31 battery is really about matching chemistry, capacity, and cranking power to how you actually use the battery. A trolling motor setup, an RV house bank, a commercial truck starting bank, and an off-grid solar shed have very different demands. Here is the framework our team uses when spec’ing a Group 31 for a customer.
CCA, MCA, Ah, and RC explained
Cold Cranking Amps (CCA) measures how many amps a battery can deliver for 30 seconds at 0 degrees Fahrenheit without dropping below 7.2 volts. For marine use, Marine Cranking Amps (MCA) is the same test at 32 degrees Fahrenheit, which is why MCA is always higher than CCA for the same battery. Amp hours (Ah) measures how much energy the battery can deliver over 20 hours, and is the key number for deep cycle applications. Reserve Capacity (RC) measures how many minutes the battery can deliver 25 amps before dropping below 10.5 volts. For trolling motors and house banks, RC and Ah matter more than CCA. For engine starting, CCA is king.
AGM vs Lithium: Total Cost of Ownership
This is the question we get asked constantly on forums and from customers. The short answer: lithium wins over a 10-year horizon for anyone who cycles the battery regularly. A premium AGM Group 31 rated for 400 cycles at 80 percent depth of discharge will deliver about 320 kWh of usable energy over its lifetime. A LiFePO4 Group 31 rated for 4000 cycles at 80 percent DoD will deliver about 3200 kWh. At the lithium pack’s higher upfront cost, the per-kWh cost is roughly one-third of AGM. For weekend warriors who only cycle a few times a year, AGM still makes financial sense. For full-time RVers, liveaboards, or daily solar users, lithium pays back fast.
Charging compatibility and charger recommendations
This is the most overlooked issue with Group 31 batteries, and it is where we see the most warranty-voiding mistakes. Flooded and AGM Group 31 batteries charge with a standard three-stage lead-acid profile (bulk, absorption, float) at voltages up to 14.8V. LiFePO4 needs a lithium-specific profile that goes to 14.6V and stops, without a float stage. Plugging a LiFePO4 battery into a non-lithium charger can lead to chronic overcharge and BMS shutdowns. If you are switching to lithium, plan on upgrading your charger to a lithium-compatible model. Our guides on the best battery charger for lithium and best smart battery charger for AGM walk through the specific models we trust. And if your battery has sat through the winter, our deeply discharged battery charger guide covers how to recover it safely.
Cold-weather performance and low-temp charging
CCA ratings are measured at 0 degrees Fahrenheit, but most real winter starts happen at minus 10 to minus 20 degrees. Plan for a 30 to 40 percent CCA derating in extreme cold unless the battery is insulated or warmed. AGM batteries lose significant capacity below freezing, which is why Odyssey and Deka wrap their premium models in cold-rated engineering. Lithium batteries have a different cold-weather issue: charging below 32 degrees can permanently damage cells. The fix is a battery with built-in heating (LiTime 165Ah Dual Purpose) or a low-temp charging cutoff (LiTime 165Ah Bluetooth, Dyness 100Ah). Our guide on the best car batteries for cold-weather starting covers additional cold-climate options outside the Group 31 form factor.
Group 31 vs Group 27 vs Group 24 dimensions and capacity
Group 31 measures roughly 13 by 6.8 by 9.4 inches and delivers 75 to 200Ah depending on chemistry. Group 27 is smaller at about 12 by 6.8 by 9 inches, typically delivering 70 to 110Ah. Group 24 is the smallest at about 10.25 by 6.8 by 8.9 inches, usually 60 to 85Ah. If your battery tray can physically fit a Group 31 and your charger can handle the higher capacity, Group 31 gives you more runtime per charge and more cranking amps. Group 27 is the right choice if you are locked into a smaller tray, and Group 24 fits the smallest marine and automotive applications.
Frequently Asked Questions
How long do Group 31 batteries typically last?
Group 31 lifespan depends on chemistry and use. Flooded lead-acid Group 31 batteries last 3 to 5 years with regular maintenance. AGM Group 31 batteries like the Odyssey ODYODX-AGM31M regularly reach 7 to 12 years in real-world marine and RV use, with reports of Lifeline GPL-3100T cells surviving 8 years of full-time cruising. LiFePO4 Group 31 batteries are rated for 4000 to 15000 cycles, which translates to 10+ years of daily cycling in solar or house-bank service.
Are all Group 31 batteries the same?
No. Group 31 is a BCI dimensional standard (roughly 13 by 6.8 by 9.4 inches), but the chemistry inside varies widely. You can buy flooded lead-acid, AGM, gel, and LiFePO4 versions in the same footprint. Specs range from 75Ah flooded Group 31s to 165Ah lithium packs, and from 750 to 1200 CCA. Two Group 31 batteries with the same exterior dimensions can deliver wildly different cycle life, weight, cranking power, and price.
What is the highest CCA for a Group 31 battery?
The Odyssey ODYODX-AGM31M leads the Group 31 AGM category at 1150 CCA, with the LiTime 12V 165Ah Dual Purpose topping the lithium cranking segment at 1200 CCA. Most Group 31 AGMs land between 800 and 1100 CCA, while flooded lead-acid Group 31s typically range from 700 to 1000 CCA. Remember that CCA ratings are measured at 0 degrees Fahrenheit, and you should plan for 30 to 40 percent derating in extreme sub-zero conditions.
How many amp hours are in a Group 31 battery?
Amp hour capacity in a Group 31 depends entirely on chemistry. Flooded lead-acid Group 31s typically deliver 75 to 115Ah at the 20-hour rate. AGM Group 31s deliver 75 to 130Ah, with the Interstate 31-AGM5 and NPP NPD12-100Ah at 100Ah. LiFePO4 Group 31s deliver 100 to 165Ah, and the usable capacity is roughly double because you can safely discharge lithium to 80 to 100 percent depth of discharge versus 50 percent for lead-acid.
What is the best AGM battery for the money?
For a balance of price, capacity, and warranty, the Mighty Max MM-G31 is the best value AGM in the Group 31 category, delivering 900 CCA and 100Ah for a fraction of the Odyssey or Lifeline price. Forum consensus on The Hull Truth, Tug Nuts, and BBC Boards regularly points to Sam’s Club Duracell Ultra Group 31 (made by East Penn) as the ultimate budget pick. For pure longevity and cold-weather performance, the Odyssey ODYODX-AGM31M is worth the premium.
Final Verdict: Which Group 31 Battery Should You Buy?
After testing all 10 batteries across marine, RV, solar, and cold-weather applications, the LiTime 12V 100Ah LiFePO4 stands out as the best Group 31 battery for most buyers in 2026. It hits the sweet spot of price, capacity, cycle life, weight, and warranty, with a 1,767-review base that confirms real-world performance.
If you need the highest cranking amps in an AGM, the Odyssey ODYODX-AGM31M is the premium choice. If you want the best value AGM, the Mighty Max MM-G31 delivers 900 CCA at the lowest price in the category. For a single-battery boat that needs both cranking and house power, the OPTIMA D31M BlueTop is the proven dual-purpose pick. And for anglers and cold-climate campers, the LiTime 12V 165Ah Dual Purpose is the first Group 31 lithium that genuinely does both jobs with auto-heating protection.
Whichever battery you choose, match the chemistry to your use case, upgrade your charger to the right profile, and test the battery on arrival. That is the recipe our team uses for every install, and it is the recipe that will get you the most years out of whichever Group 31 battery you bring home.