Buying Guide
5 Best Group 31 Deep Cycle Batteries in 2026: A Practical Camping Guide
Best Group 31 deep cycle batteries for camping and RV banks, comparing dual-purpose AGM, flooded and lithium options by capacity and starting power.
Group 31 is a larger BCI case than Group 24 or 27, commonly around 13 inches long and 6.8 inches wide, and it fits many boat, truck and camper battery trays. Because the format is shared by starting, dual-purpose and true deep cycle batteries, the label on the case matters as much as the size.
Five Group 31 batteries are compared here: three dual-purpose AGM units, one pair of flooded deep cycle batteries and one lithium drop-in. They were judged on listed capacity, cranking claims, terminals, chemistry and how each is meant to be used.
Danny’s Camping field notes
The Campsite Fit Check
A quick way to connect the shortlist to the space, workload and ownership details that matter after the box arrives.
- Start with the job
- LiTime 12V 100Ah Group 31 LiFePO4 Deep Cycle Battery for RV Marine Solar leads this shortlist for Lightweight house battery. Use that fit as a reference point, then compare the alternatives against your own space and workload.
- Specs that separate the picks
- The first details to compare are 12V 100Ah LiFePO4, 12V 110Ah, 825 CCA. Confirm the exact model and included components before ordering.
- Trade-off to plan for
- Not meant for engine starting
The Practical Shortlist
A practical look at 5 options, organized around the job each one suits best.
Best Overall
LiTime 12V 100Ah Group 31 LiFePO4 Deep Cycle Battery for RV Marine Solar
Lightweight house battery
Our take Check price for LiTime 12V 100Ah Group 31 LiFePO4 Deep Cycle Battery for RV Marine Solar (opens in a new tab)
Best Dual-Purpose AGM
Mighty Max Battery MM-G31M
Truck camper starting and house use
Our take Check price for Mighty Max Battery MM-G31M (opens in a new tab)
Best Budget Dual-Purpose
Weize BCI Group 31M Dual Purpose AGM Battery
Budget dual-purpose use
Our take Check price for Weize BCI Group 31M Dual Purpose AGM Battery (opens in a new tab)
Best Replacement for Optima D31M
Deep Cycle Marine Battery
Direct D31M replacement
Our take Check price for Deep Cycle Marine Battery (opens in a new tab)
Best Flooded Deep Cycle Pair
US Battery US31DC XC2 12V Flooded Lead Acid Deep Cycle Battery
Fixed deep cycle banks
Our take Check price for US Battery US31DC XC2 12V Flooded Lead Acid Deep Cycle Battery (opens in a new tab)
Why You Can Trust Danny’s Camping
At Danny’s Camping, we compare products based on campsite fit, verified specifications, usability, setup requirements, weight, durability, and real-world trade-offs. We do not rank products purely on marketing claims or commission rates.
We have not personally tested every product listed. Where hands-on testing is not available, recommendations are based on verified manufacturer specifications, product documentation, use-case fit, and comparative research.
Why Each Pick Made the Cut
Best Overall· 1 of 5
LiTime 12V 100Ah Group 31 LiFePO4 Deep Cycle Battery for RV Marine Solar
Danny’s Take
The pick for anyone who wants Group 31 fit with lithium weight.
Best for
- Lightweight house battery
Why it made the shortlist
The LiTime is a 12V 100Ah Group 31 LiFePO4 battery with a 100A BMS that guards against overcharge, over-discharge, short circuit and over-temperature. It weighs 22.05 lb, about a third of a comparable lead acid battery, and the listing claims 15000 or more cycles.
Against the AGM dual-purpose batteries, it gives full 100Ah use and a fraction of the weight, with no cranking claim in the listing. Compared with the flooded US Battery pair, it needs no watering and no venting routine.
It suits campers and van owners swapping a heavy Group 31 lead acid for a lighter house battery. The 5 year warranty and tech support add a layer of assurance.
Key dimensions & specs
- 12V 100Ah LiFePO4
- 100A BMS, 22.05 lb
- 5 year warranty
Pros
- About a third the weight of lead acid
- 100A BMS with several protections
- 5 year warranty listed
- Fits Group 31 trays
Cons
- Not meant for engine starting
- Needs a lithium charge profile
The Catch
A lithium battery needs a charger or controller with a LiFePO4 profile.
Best Dual-Purpose AGM· 2 of 5
Mighty Max Battery MM-G31M
Danny’s Take
A sealed AGM that can do both jobs in a vehicle with one tray.
Best for
- Truck camper starting and house use
Why it made the shortlist
The Mighty Max MM-G31M is a 12V 110Ah Group 31M AGM that lists 825 CCA, 1000 MCA and 240 minutes of reserve capacity. It is spill-proof, maintenance free and rated for up to 700 cycles at 50% depth of discharge.
Against the Weize it states a cycle rating, which gives a better view of its deep cycle life. Compared with the LiTime, it can crank an engine and run house loads at a much higher weight.
It suits truck campers and boat owners who want one battery to start an engine and run lights. The sealed design avoids acid leaks in a vehicle.
Key dimensions & specs
- 12V 110Ah, 825 CCA
- 1000 MCA, 240 RC
- 700 cycles at 50%
Pros
- Starts engines and runs house loads
- Cycle life stated at 50% depth
- Spill-proof and maintenance free
- 110Ah of listed capacity
Cons
- Dual-purpose is not true deep cycle
- Heavier than lithium packs
The Catch
A dual-purpose battery tolerates deep cycling less well than a true deep cycle model.
Best Budget Dual-Purpose· 3 of 5
Weize BCI Group 31M Dual Purpose AGM Battery
Danny’s Take
The cheapest way into a sealed Group 31M that starts and cycles.
Best for
- Budget dual-purpose use
Why it made the shortlist
The Weize is a 12V 110Ah Group 31M AGM with 825 CCA and 240 minutes of reserve capacity for starting and deep cycling. Its listing highlights leak-proof construction, specialised safety valves and quick-charge capability at 14.4V.
Its price is the lowest in this comparison, and it matches the Mighty Max on cranking figures. Against the Banshee it lists a higher capacity of 110Ah and names a charge voltage.
It suits budget trucks and campers that need a Group 31M that can start an engine and power a few accessories. A sealed leak-proof case suits use in a vehicle.
Key dimensions & specs
- 12V 110Ah, 825 CCA
- 240 min reserve capacity
- 14.4V charge voltage named
Pros
- Names a 14.4V charging voltage
- Leak-proof sealed case
- Dual-purpose cranking figures listed
Cons
- No cycle life figure stated
- Heavy compared with lithium
The Catch
The listing does not state cycle life, so treat it as an occasional-deep-cycle battery.
Best Replacement for Optima D31M· 4 of 5
Deep Cycle Marine Battery
Danny’s Take
A swap-in battery for owners matching an existing D31M footprint.
Best for
- Direct D31M replacement
Why it made the shortlist
The Banshee is a Group 31 marine deep cycle with top posts, 105Ah, 800 CCA and dual post terminals. Its listing says it replaces the Optima D31M 8052-161 SC31DM.
Against the Weize and Mighty Max it lists slightly less capacity at 105Ah and 800 CCA.
It suits owners replacing an existing D31M-style battery who want a direct match. The dual posts simplify mixed accessories.
Key dimensions & specs
- 12V 105Ah Group 31
- 800 CCA, top post
- Dual post terminals
Pros
- Lists a direct Optima D31M replacement
- Dual post terminals for accessories
- Marine deep cycle design
- 800 CCA listed
Cons
- Short feature list
- No cycle or reserve figure stated
The Catch
The listing is brief, so confirm terminal layout against your cable runs.
Best Flooded Deep Cycle Pair· 5 of 5
US Battery US31DC XC2 12V Flooded Lead Acid Deep Cycle Battery
Danny’s Take
The capacity leader for a bank that stays in place.
Best for
- Fixed deep cycle banks
Why it made the shortlist
The US31DC XC2 pair is rated 130Ah at the 20 hour rate with runtime ratings of 59 minutes at 75 amps and 225 minutes at 25 amps. It uses flooded lead acid cells with Diamond Plate Technology, dual SAE and bolt terminals and a heat-sealed polypropylene case.
Against the AGM dual-purpose batteries, it lists far more deep cycle capacity at 130Ah per battery and publishes runtime ratings. Next to the LiTime, it costs much more as a pair and weighs more.
It suits a fixed camper or cabin bank where long deep cycle life matters more than weight. Two batteries wired in parallel give 260Ah.
Key dimensions & specs
- 12V 130Ah flooded pair
- Runtime ratings at three loads
- Dual SAE and bolt terminals
Pros
- Highest listed capacity at 130Ah
- Commercial heat-sealed case
- Sold as a pair
Cons
- Flooded cells need watering and venting
The Catch
Flooded batteries vent hydrogen and need ventilation away from any tent.
How We Built This Shortlist
Each pick was assessed across 4 criteria weighted for real-world use.
- Group 31 and 31M labels
- Each listing was checked for the named Group 31 or 31M size and the terminal layout.
- Deep cycle versus dual-purpose
- Cranking figures, reserve capacity and cycle ratings were read to see which jobs each battery supports.
- Capacity and chemistry
- Listed amp hours and the flooded, AGM or lithium chemistry were compared for weight and maintenance.
- Terminals and fit
- Post type and any direct replacement notes were checked against common trucks, boats and campers.
What Matters Before You Choose a Group 31 Deep Cycle Battery
Key buying criteria so you get the right fit the first time.
Starting versus deep cycle
A starting battery is built to deliver a burst of current, while a deep cycle battery is built to be drained and recharged many times. Dual-purpose batteries try to do both, but they usually tolerate deep discharge less well than a true deep cycle. Read the listing for cycle figures and choose a deep cycle battery for a house bank.
CCA and reserve capacity
Cold cranking amps tell you how well a battery starts an engine in the cold, while reserve capacity in minutes shows how long it runs a 25A load. Camper house loads depend more on reserve capacity and amp hours. Compare both numbers when the listing gives them.
Terminal type
Top posts, SAE posts and bolt terminals each need compatible cable ends. A battery with dual posts can accept both. Check the terminal in the listing against your existing cables before ordering.
Weight and tray fit
Group 31 lead acid batteries can weigh over 60 lb, which matters when a tray is above a tool box or inside a camper. Lithium cuts that to roughly 22 lb. Check dimensions as well as the group number, since manufacturers vary slightly.
Charging, fuse and vent
AGM and lithium need different charging voltages, and flooded batteries need ventilation. Put a fuse or breaker close to the positive terminal and use cable sized for the load. Keep batteries secured and away from a sleeping area or tent.
Match a Group 31 Deep Cycle Battery to Your Camp Setup
By Use
| Your situation | Recommended pick | Why |
|---|---|---|
| Lightweight camper house bank | LiTime Group 31 100Ah | Lithium at 22.05 lb |
| Truck camper that must start | Mighty Max MM-G31M | 825 CCA with a stated cycle rating |
| Lowest price sealed | Weize Group 31M AGM | Dual-purpose AGM at the lowest price |
| Replacing a D31M | Banshee Group 31 | Lists Optima D31M replacement |
| Fixed bank with the most capacity | US Battery US31DC XC2 | 130Ah flooded pair |
Scroll sideways to see every column.
By Budget
| Budget | Recommended pick |
|---|---|
| $220 to $240 | Weize Group 31M AGM or Banshee Group 31 |
| $240 to $290 | Mighty Max MM-G31M or LiTime Group 31 100Ah |
| $860 to $870 | US Battery US31DC XC2 |
Dual-Purpose vs Deep Cycle
- Dual-purpose
- Mighty Max MM-G31M, Weize Group 31M AGM and Banshee Group 31 list cranking amps and can start an engine. They tolerate deep discharge less than a true deep cycle battery.
- Deep cycle
- LiTime Group 31 100Ah and US Battery US31DC XC2 are built for repeated discharge and do not list cranking claims. They suit house banks, not engine starting.
Most campers should default to the LiTime Group 31 100Ah for house power, unless one battery must also start an engine.
By Maintenance Preference
| Preference | Recommended pick |
|---|---|
| No upkeep and light weight | LiTime Group 31 100Ah |
| Sealed lead acid | Mighty Max MM-G31M |
| Cheapest sealed battery | Weize Group 31M AGM |
| Willing to water flooded cells | US Battery US31DC XC2 |
For Truck Campers Specifically
- Look for
- A battery that states both cranking amps and deep cycle capacity, with a terminal layout that matches your cables.
- In this comparison
- Mighty Max MM-G31M and Weize Group 31M AGM both list 825 CCA and 110Ah, so they can start an engine and run house loads.
When to Spend More
- Spend more if
- Spend more on the LiTime Group 31 100Ah for low weight and a 5 year warranty, or the US Battery US31DC XC2 for flooded capacity of 130Ah per battery.
- Save if
- Save with the Weize Group 31M AGM for the lowest price dual-purpose sealed battery, or the Banshee Group 31 for a direct D31M-style swap.
Before You Bring One Home
What is a Group 31 battery?
Group 31 is a BCI size for large batteries, around 13 inches long and 6.8 inches wide. It fits many boat trays, trucks and campers. Always check the listed dimensions, since 31M marine versions can differ.
Can I use a dual-purpose battery as a house battery?
Yes for light use, but it handles deep discharge less well than a true deep cycle battery. Keep discharge shallow and recharge promptly. For daily off-grid use, a deep cycle or lithium battery lasts longer.
Is lithium worth it in Group 31?
If weight and usable capacity matter, lithium is a strong upgrade, as the LiTime weighs about 22 lb. It does not crank engines and needs a lithium charge profile. AGM or flooded is cheaper if the battery stays put.
How do I charge a Group 31 AGM?
Use an AGM-compatible charger or a controller set to the AGM profile, around 14.4V for bulk charging as one listing names. Avoid overcharging. Charge promptly after use.
How do I keep a flooded Group 31 healthy?
Check water levels, keep the terminals clean and charge in a ventilated space. Never charge near sparks or inside a closed tent. Wear eye protection when handling.
Bottom Line
Best overall: LiTime 12V 100Ah Group 31 LiFePO4 Deep Cycle Battery for RV Marine Solar — best overall pick in this roundup. See the full verdicts above for every pick, with pros, cons and who each one suits.
Browse all group 31 deep cycle batteries on Amazon — Prime-eligible options with current pricing.
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About the author
Danny Walker
Founder & Lead Editor at Danny’s Camping
Danny covers camping gear, campsite setup, outdoor power, sleep systems, and practical camping advice, with a focus on helping campers make better gear decisions.