Best BCI Group 31 Batteries

odyssey 31m pc2150 1mBCI group 31 batteries are very popular batteries, commonly used in automotive, marine, industrial, off-the-grid and other similar applications where the batteries are often pushed to their limits.

Group 31 batteries differ in internal construction and exact chemistry, with the lead-acid AGM and Gel group 31 batteries being most common, and with lithium group 31 batteries becoming more and more popular.

Sealed Lead Acid (SLA) AGM (Absorbent Glass Mat) batteries are commonly used as starting, dual purpose and deep cycle batteries, while SLA Gel batteries are used for off-the-grid deep cycle applications like solar and wind batteries, backup batteries and similar.

Lithium BCI group 31 batteries feature similar capacity like AGM and Gel group 31 batteries, but they are 2-3x lighter and often support 4-8x more charging/discharging cycles. And lithium batteries cost several times more than AGM/Gel batteries.

Group 31 Battery Dimensions

Stadnard group 31 battery dimensions (L x W x H) are 13 x 6.8125 x 9.4375 inches (330 x 173 x 240 mm) and on average they feature nominal (20h) capacity between 75-125 Ah, typical CCA of 600-1150 Amps and typical RC value of 155-240 minutes.

The main reason for such wide range of values are very popular Optima batteries that feature spiral wound cells and have 'empty space' between the cells.

While Optima batteries are not the most efficient in terms of used total volume, they are very vibration resistant, their dual purpose/deep cycle batteries tolerate large number of charging/discharging cycles, their starting batteries have excellent CCA/MCA features etc.

The following table lists the most popular group 31 batteries - batteries are ordered alphabetically:

Model Battery Type Cell Type Ah CCA MCA RC Weight (lbs/kg) Review
AIMS Power AGM12V100A Deep Cycle AGM 100 - - - 70.5 lbs; ~32 kg -
AIMS Power LFP12V100A Deep Cycle LiFePO4 100 - - - 30.2 lbs; 13.7 kg  -
Battle Born 100Ah 12V LiFePO4 Deep Cycle LiFePO4 100 - - - 29 lbs; 13.2 kg  Battle Born 100Ah 12V LiFePO4
Bioenno Power BLF-12100WS Deep Cycle LiFePO4 100 - - - 28.1 lbs; 12.8 kg -
Exide XMC-31 Deep Cycle AGM 100 925 1110 200 68 lbs; 31 kg Exide XMC-31
ExpertPower EP12100 Deep Cycle LiFePO4 100 - - - 29.7 kg; 13.5 kg -
ExpertPower EXP100 Deep Cycle AGM 100 - - - 63.94 lbs; 30 kg -
GreenLiFE Battery GL100 Dual Purpose LiFePO4 100 - - 240 28 lbs; 12.7 kg -
Lifeline GPL-31T Deep Cycle AGM 105 600 750 195 69 lbs;  31.5 kg -
Lifeline GPL-31XT Deep Cycle AGM 125 650 800 230 69 lbs; 31.5 kg -
Lifeline GPL-3100T Dual Purpose AGM 100 810 950 228 67 lbs; 30.4 kg -
Miady LFP100AH Deep Cycle LiFePO4 100 - - - 28.9 lbs; 13.1 kg -
NorthStar ELT-AGM31 Dual Purpose AGM 100 925 1050 190 65.7 lbs; 29.8 kg -
NorthStar NSB-AGM31 Dual Purpose AGM 103 1150 1370 220 75 lbs; 34.0 kg -
NorthStar NSB-AGM31M Dual Purpose AGM 103 1150 1370 220 75 lbs; 34.0 kg  -
Odyssey 31M-PC2150 Dual Purpose AGM 100 1150 1370 205 77.8 lbs; 35.3 kg  Odyssey 31M-PC2150 
Optima 8052-161 D31M Dual Purpose AGM 75 900 1125 155 59.8 lbs; 27.1 kg Optima 8052-161 D31M 
Renogy RNG-BATT-AGM12-100 Deep Cycle AGM 104 - - 180+ 66 lbs; 29.9 kg -
Renogy RNG-BATT-GEL12-100 Deep Cycle Gel 100 - - 180+ 60 lbs; 27.2 kg Renogy 12V 100Ah Deep Cycle Pure Gel and Hybrid Gel Batteries  
Renogy RBT100GEL12-G1 Deep Cycle Gel 100 - - ~175 63.9 lbs; 29 kg
Trojan T31-GEL Deep Cycle Gel 102 - - 200 70 lbs; 31.7 kg -
UPG UB121100 Deep Cycle AGM 110 - - - 65.7 lbs; 29.8 kg -
VMAXTANKS SLR125 Deep Cycle AGM 125 - - 260 75 lbs; 34 kg VMAXTANKS Batteries V30-800, V35-857, MR96, MR107, SLR125, MR137, SLR155 and MR197 Comparison
VMAXTANKS MR137-120 Deep Cycle AGM 120 - 900 230 75 lbs; 34 kg
XS Power XP3000 Deep Cycle AGM 120 - - 240 73 lbs;  33.1 kg -
Weize LFP12100 AGM Deep Cycle AGM 100 - - - 60 pounds; 27.2 kg -
Weize LFP12100 Gel Deep Cycle Gel 100 - - <180 67 pounds; 30.4 kg -
WindyNation BAT-NSAP12-100 Deep Cycle AGM 106 - - - 67 lbs; 30.4 kg WindyNation BAT-NSAP12-100

Note: Amazon affiliate links open in the new windows, feel free to check them for the most up-to-date offers and prices.

As one can see, true starting group 31 batteries are practically non-existent - these batteries are large enough that even dual purpose batteries are able to provide up to 1150 CCA and 1370 MCA, with 5s pulse currents being in 1500+ Amps range. Obviously, not all models are able to provide such currents.

On the other hand, deep cycle group 31 batteries feature Reserve Capacity up to 260 minutes and nominal capacity of up to 125 Ah.

While lead-acid group batteries weigh on average 60-75 pounds (27.2 - 34 kg), lithium group 31 batteries weigh on average 28-30 pounds (12.7 - 13.6 kg), while providing similar nominal capacity, but also much larger number of charging/discharging cycles.

Group 29 vs Group 31 Batteries

BCI Group 29 consists of two very similar battery groups, with their dimensions of (L x W x H):

- Group 29NF: 13 x 5.5 x 8.9375 inches (330 x 140 x 227 mm),

- Group 29H: 13.125 x 6.75 x 9.125 inches (334 x 171 x 232 mm).

With its dimensions of 13 x 6.8125 x 9.4375 inches (330 x 173 x 240 mm), group 31 batteries are larger than the group 29NF, and somewhat shorter than the group 29H batteries, but also wider and taller than the group 29H batteries.

Due to the very small maximum length difference between group 31 and group 29H batteries (some 0.125 inches, 4 mm), group 29H battery probably can fit group 31 battery compartments, but, just to be sure if you want to replace old group 31 battery with the new group 29H battery, be sure to measure your battery compartment and to check exact battery dimensions of the group 29H battery in question.

Group 30H vs Group 31 Batteries

The difference in size between group 30H and group 31 batteries is very small and these batteries are often used interchangeably. But, just in case note that the exact maximum dimensions are (L x W x H):

- Group 30H: 13.5 x 6.8125 x 9.25 inches (343 x 173 x 235 mm),

- Group 31: 13 x 6.8125 x 9.4375 inches (330 x 173 x 240 mm).

Group 31 batteries may be taller, they have the same width like group 30H batteries, but group 31 batteries are somewhat shorter (0.5 inches, ~13 mm).

Again, group 31 and 30h may be used interchangeably if they can fit into the required battery compartment.

Note: some manufacturers label their batteries as 'group 31 batteries' although the length of their batteries is more than 13 inches (330 mm) and their batteries actually belong to the 30H group. That is why we always try to verify exact battery dimensions.

Group 31 Batteries as Trolling Motor Batteries

vmaxtanks slr125Group 31 batteries are commonly used as energy source for electric trolling motors. Electric trolling motors rarely feature maximum current of more than 50 Amps - if more thrusts are required, electric trolling motors are designed to operate at 24 or even 36 volts.

Also, most of the time trolling motors are not operated at full thrust - if they are, then they are not dimensioned properly and they lack the power for emergencies.

Thus, when trying to find out which battery is good as trolling motor battery, check its Reserve Capacity - a value given in minutes that the battery is able to provide 25 Amps of current before the voltage drops below 10.5 volts at 77°F (25°C).

Lithium group 31 batteries are much lighter and rarely have RC value given. But, lithium trolling batteries don't feature as strong capacity loss as lead-acid batteries due to the large discharge currents, so 100Ah lithium battery usually feature RC value around ~230 minutes (very close to the theoretical value of 240 minutes).

As trolling batteries, lithium group 31 batteries are used where lower mass is important, for example, as kayak trolling battery and similar.

Most popular group 31 trolling motor batteries are VMAXTANKS SLR125 (260 minutes RC), Renogy RNG-BATT-GELL12-100 ('Pure Gel', large number of charging cycles), Weize LFP12100 AGM and Gel models (affordable price) etc.

Group 31 Batteries as Solar/Wind Batteries

renogy 12v 100ah pure gel 1Solar/Wind batteries are off-the-grid batteries featuring almost no maintenance, good tolerance to deep discharge conditions leading to large number of charge/discharge cycles.

Since these batteries are used mostly during the night and charged during the day, they don't require large maximum allowed charging/discharging currents, although some systems with wind turbines may benefit greatly if the batteries may be charged with strong currents.

Also, since off-the-grid systems usually feature large capacity battery banks, individual price of the battery is very important.

The best solar/wind group 31 batteries are Renogy RNG-BATT-GELL12-100 (balanced price, large number of charging/discharging cycles, low charging current), Weize LFP12100 Gel, WindyNation BAT-NSAP12-100, VMAXTANKS SLR125, Trojan T31-Gel, Lifeline GPL-31XT, etc.

Since solar/wind batteries are commonly used in fixed applications, their weight is not that important. However, if you need a good lightweight solar/wind battery, consider lithium batteries - they are 2-3x lighter, they offer 4-8x more charging/discharging cycles, they do cost several times more and one should carefully check the electric installation prior their installation, especially the 'charging' part.

Group 31 Batteries as Sump Pump Backup Batteries

Sump pump strength is usually labeled in HP and it varies from small 0.25 and 0.5 HP pumps to large 2-3 and even more HPs.

Note: HP value varies depending on its definition, but generally 1 HP equals to 746 watts.

Thus, 12V battery when powering different sump pumps must be able to provide:

- 0.25 HP: 186.5 watts, ~16 Amps @12 volts,

- 0.50 HP: 373 watts, ~32 Amps @12 volts,

- 0.75 HP: ~560 watts, ~47 Amps @12 volts,

- 1.00 HP: 746 watts, ~63 Amps @12 volts.

1 HP and stronger sump pumps sometimes feature 24 or even 36 volts backup systems, requiring more batteries.

Sump pump backup system may wait for months and years before they are needed and when that happens, they must operate reliably - periodically, these systems are tested and if required, they are serviced.

Typical group 31 AGM/Gel cell battery features on average nominal capacity of 100-105 Ah and when it is used to power, for example, 0.50 HP sump pump, it must be able to provide ~32 Amps for as long as possible. Since lead-acid batteries' capacity decreases as the discharging current is increased, operating time under 32 Amps load should be checked in the discharging tables/graphs of each battery.

On average, 100-105 Ah battery should be able to power 32 Amps load for at least 2 hours constantly (again, that is two (2) hours, not three (3) hours).

Since sump pumps are not operating constantly, but more on On/Off principle, these 2 hours 'constantly' may in real life last much longer...

Group 31 Batteries as Automotive and RV Battery

odyssey 31m pc2150 1As automotive batteries, group 31 batteries are used as dual purpose batteries in the single battery electric systems or as both starting and deep cycle batteries in dual battery electric systems, commonly found in Recreational Vehicles (RV).

In cars and trucks, single group 31 battery is used for starting the main engine, but also for powering various loads while the main engine is off like alarm systems, lights, GPS, ventilators etc. Also, battery in such systems may be used for powering various pumps, winches and other larger loads.

Perhaps the best group 31 batteries for this purpose are NorthStar NSB-AGM31 and Odyssey 31M-PC2150. Both batteries are available in several sub-models and feature 1150 CCA and 1370 MCA amps - and that is a lot of power.

While NorthStar NSB-AGM31 feature slightly higher capacity and RC, Odyssey 31M-PC2150 is somewhat better performer at low temperatures and tend to be somewhat more robust - but, this 'somewhat' is almost negligible.

If you are looking for premium dual purpose group 31 battery, go for either Odyssey 31M-PC2150 or NorthStar NSB-AGM31, it is your choice :)

optima d31m bluetopAnother group 31 batteries that may be used as very good dual purpose batteries in cars and trucks are Exide XMC-31 which is not always available on the market and spirally wound Optima 8052-161 D31M.

Optima 8052-161 D31M features the smallest capacity of all group 31 batteries (only 75 Ah), but it also features 155 min RC (180 min theoretical RC), 900 CCA and 1125 MCA, which is excellent result for 75 Ah dual-purpose battery.

Also, Optima 8052-161 D31M is the lightest lead-acid group 31 battery.

All these reasons make Optima 8052-161 D31M one of the most popular general purpose group 31 automotive batteries.

Dual battery electric systems commonly use one starting battery for cranking the main engine and one battery or battery pack for deep cycle applications.

As starting only battery, Optima 8052-161 D31M is recommended model since it is the lightest group 31 battery, but it is also one of the strongest.

As deep cycle battery or battery pack, one should go for the battery that is able to provide energy for required load - if the load is on average ~25 Amps, check the RC values, and if the loads are 4-7 Amps, check the nominal capacity of the batteries.

Also, don't forget to check the price of the batteries and the number of supported charging/discharging cycles.

Lithium batteries may be used as RV house batteries, leading to large weight savings, but they require larger initial investment and perhaps some changes to onboard charging system.

The Best Group 31 Battery?

 It is rather hard to say which group 31 battery is the best.

It all depends on the application type and requirements. It makes no sense to spend money on NorthStar or Odyssey batteries for some standby system that is used, for example, every few months and provides 10-15 Amps for few hours.

Also, it makes no sense and can be dangerous to buy the cheapest group 31 battery and expect it to withstand use (and abuse) during Alaskan winter as industrial/truck battery, etc.

So, when picking up 'the best group 31 battery' be sure to choose according to your own needs and preferences:

Model Battery Type Cell Type Ah CCA MCA RC Weight (lbs/kg) Review
AIMS Power AGM12V100A Deep Cycle AGM 100 - - - 70.5 lbs; ~32 kg -
AIMS Power LFP12V100A Deep Cycle LiFePO4 100 - - - 30.2 lbs; 13.7 kg  -
Battle Born 100Ah 12V LiFePO4 Deep Cycle LiFePO4 100 - - - 29 lbs; 13.2 kg  Battle Born 100Ah 12V LiFePO4
Bioenno Power BLF-12100WS Deep Cycle LiFePO4 100 - - - 28.1 lbs; 12.8 kg -
Exide XMC-31 Deep Cycle AGM 100 925 1110 200 68 lbs; 31 kg Exide XMC-31
ExpertPower EP12100 Deep Cycle LiFePO4 100 - - - 29.7 kg; 13.5 kg -
ExpertPower EXP100 Deep Cycle AGM 100 - - - 63.94 lbs; 30 kg -
GreenLiFE Battery GL100 Dual Purpose LiFePO4 100 - - 240 28 lbs; 12.7 kg -
Lifeline GPL-31T Deep Cycle AGM 105 600 750 195 69 lbs;  31.5 kg -
Lifeline GPL-31XT Deep Cycle AGM 125 650 800 230 69 lbs; 31.5 kg -
Lifeline GPL-3100T Dual Purpose AGM 100 810 950 228 67 lbs; 30.4 kg -
Miady LFP100AH Deep Cycle LiFePO4 100 - - - 28.9 lbs; 13.1 kg -
NorthStar ELT-AGM31 Dual Purpose AGM 100 925 1050 190 65.7 lbs; 29.8 kg -
NorthStar NSB-AGM31 Dual Purpose AGM 103 1150 1370 220 75 lbs; 34.0 kg -
NorthStar NSB-AGM31M Dual Purpose AGM 103 1150 1370 220 75 lbs; 34.0 kg  -
Odyssey 31M-PC2150 Dual Purpose AGM 100 1150 1370 205 77.8 lbs; 35.3 kg  Odyssey 31M-PC2150 
Optima 8052-161 D31M Dual Purpose AGM 75 900 1125 155 59.8 lbs; 27.1 kg Optima 8052-161 D31M 
Renogy RNG-BATT-AGM12-100 Deep Cycle AGM 104 - - 180+ 66 lbs; 29.9 kg -
Renogy RNG-BATT-GEL12-100 Deep Cycle Gel 100 - - 180+ 60 lbs; 27.2 kg Renogy 12V 100Ah Deep Cycle Pure Gel and Hybrid Gel Batteries  
Renogy RBT100GEL12-G1 Deep Cycle Gel 100 - - ~175 63.9 lbs; 29 kg
Trojan T31-GEL Deep Cycle Gel 102 - - 200 70 lbs; 31.7 kg -
UPG UB121100 Deep Cycle AGM 110 - - - 65.7 lbs; 29.8 kg -
VMAXTANKS SLR125 Deep Cycle AGM 125 - - 260 75 lbs; 34 kg VMAXTANKS Batteries V30-800, V35-857, MR96, MR107, SLR125, MR137, SLR155 and MR197 Comparison
VMAXTANKS MR137-120 Deep Cycle AGM 120 - 900 230 75 lbs; 34 kg
XS Power XP3000 Deep Cycle AGM 120 - - 240 73 lbs;  33.1 kg -
Weize LFP12100 AGM Deep Cycle AGM 100 - - - 60 pounds; 27.2 kg -
Weize LFP12100 Gel Deep Cycle Gel 100 - - <180 67 pounds; 30.4 kg -
WindyNation BAT-NSAP12-100 Deep Cycle AGM 106 - - - 67 lbs; 30.4 kg WindyNation BAT-NSAP12-100

Note: Amazon affiliate links open in the new windows, feel free to check them for the most up-to-date offers and prices.

Group 31 batteries store plenty of energy and are able to provide crazy strong currents, especially if mistreated.

So, if you are unsure what to do, always ask local certified professional/battery specialist for advice - better safe than sorry.