Odyssey 31M-PC2150 (ODX-AGM31) AGM Marine Dual Purpose Battery Review and Recommendation

Odyssey 31M-PC2150 (ODX-AGM31) is a BCI group 31 battery, designed as a dual-purpose battery. As starting battery it can easily provide 1000+ CCAs and as a deep cycle battery, it comes with a 205 min RC rating.

Odyssey 31M-PC2150 is an AGM SLA battery, featuring increased resistance to vibrations, spill-proof design, two types of terminals, can operate in any position, etc.

It is one of the heaviest group 31 batteries on the market and far from being cheap, but it is also one of the best batteries in its class (if not the best) and worth every (euro)cent.

Updated: December 29, 2021.

Note: Not so long ago, Odyssey rebranded their batteries. Now, the Odyssey 31-PC2150 batteries are labeled as Odyssey ODX-AGM31 batteries, however, these are still the very same (excellent) batteries and they are still generally known as Odyssey 31-PC2150 batteries. We also use the "old" Odyssey 31-PC2150 label.

Odyssey 31M-PC2150 Features and Specifications

Technical specifications of the Odyssey 31M-PC2150 battery are given in the following table:

Its physical dimensions are 13 x 6.8 x 9.41 inches (330.2 x 172.7 x 239.0 mm) and it weighs 77.8 lbs (35.3 kg).

Odyssey 31M-PC2150 is Absorbed Glass Mat (AGM) battery - it features a non-spillable electrolyte and it can operate in any position.

Like a typical marine battery, Odyssey 31M-CP2150 features double terminals: SAE and 3/8” Stud (positive), 5/16” Stud (negative).

Odyssey 31M-PC2150 has a very low self-discharge rate - a fully charged battery can be stored for up to two years at 77ºF (25ºC) or until its voltage drops below 12V (whatever happens first). The self-discharge rate depends on the storage temperature and is given in the following table:

Storage Temperature	41°F (5°C)	59°F (15°C)	77°F (25°C)	95°F (35°C)	113°F (45°C)
Storage Time	48 months	36 months	24 months	12 months	6 months

So, after 24 months at 77°F (25°C), the fully charged battery voltage will drop down to around 12V and that battery must be charged again.

When the battery leaves the factory, it is shipped in the fully charged state and its voltage is 12.84V (or slightly higher) indicating 100% SOC (state of charge). Over time, the voltage drops slowly - if the battery OCV (Open Circuit Voltage) is over 12.65V, the battery can be installed and used as fully charged.

If the voltage is 12V or less (~35% SOC), the battery should be considered discharged and it must be charged prior to first use.

Note: Despite having a very low self-discharge rate, if You plan on storing the battery for a longer period of time, charge it fully and store it in a cool area, preferably with some intelligent battery maintainer connected to the battery.

OCV depends on the SOC and that dependency is given in the following table:

Knowing OCV is important in avoiding deep discharge conditions and prolonging the battery operating life.

Odyssey 31-PC2150 Dual Purpose Battery Versions

Odyssey 31-PC2150 is manufactured in several versions, with each version being optimized for specific use.

The main difference between these batteries are the type and orientation of battery terminals:

- Odyssey 31-PC2150 comes in two versions, having 3/8" Stud or SAE battery terminals. Often, these batteries are labeled as 'Odyssey 31-PC2150T Heavy Duty Commercial Battery' or 'Odyssey 31-PC2150S Heavy Duty Commercial Battery' and indeed, they are batteries for heavy-duty commercial use.

- Odyssey 31M-PC2150 features SAE and 3/8” Stud (positive) 5/16” Stud (negative) battery terminals. This battery is often labeled as 'Odyssey 31M-PC2150ST-M TROLLING Thunder Marine Dual Purpose Battery' since it can be used as both starting marine battery, but also as a deep cycle marine battery, including trolling fishing.

- Odyssey 31R-PC2150 is just like Odyssey 31-PC2150, it just has terminal polarities reversed left and right.

Note: all versions of 31-PC2150 batteries have the same electrical performances (capacity, RC, CCA, MCA, etc).

Extreme Deep Discharge Recovery

Odyssey 31M-PC2150 battery can be recovered from deep discharge state (down to almost 0% of remaining charge), however, such events should be avoided as much as possible.

If something like that happens to the new battery, one should charge the battery to at least 13.5V, preferably to 14.4V, allowing the battery to recover at least 97% of its nominal capacity.

If the battery is having a voltage of 0-1V, the best thing to do is to connect the battery to an advanced AGM battery charger that supports battery recovery - after analyzing the battery, such battery charger will try to recover and charge the battery according to the battery's condition.

For a 100Ah AGM battery, a battery charger with a maximum charging current of 10-20 Amps is recommended.

Again, if possible avoid such deep discharge events.

Odyssey 31M-PC2150 AGM as Starting Battery

Battery's plates are made using 99.99% pure lead, and they are densely packed providing good starting power.

The new, fully charged battery can provide 2150 Amps for 5 seconds - this is its PHCA (Pulse Hot Cranking Amps) rating, thus '2150' is part of the battery's label.

HCA (Hot Cranking Amps; 80°F, 27°C) rating is 1545 Amps, MCA (Marine Cranking Amps; 32°F, 0°C) rating is 1370 Amps and IMHO, the most important CCA (Cold Cranking Amps; 0°F, -18°C) rating is 1150 Amps.

Odyssey 31M-PC2150 battery provides 1000+ CCA and it is more than strong enough for most automotive and marine cranking applications and highly recommended model for dual purpose applications as part of single battery (or single battery pack) electrical systems commonly found in the cars, RVs, boats, yachts, etc. where both good starting power and deep cycle performances are required.

Extreme Cold Temperature Starting Performances

One of the important features of the Odyssey 31M-PC2150 battery (and other 21-PC2150 batteries) is its very good performance during extremely cold temperatures.

As said before, its CCA (Cold Cranking Amps; 0°F, -18°C) rating is 1150 Amps and as the temperature is increased, so are its cranking amps (maximum current for 30 seconds, without the voltage dropping below 7.2 V).

However, Odyssey 31M-PC2150 is designed to operate safely down to -40°F (-40°C) and that is rather cold, to say the least.

Under these temperatures (-40°F, -40°C!), Odyssey 31M-PC2150 is able to provide 550 cranking amps for 30 seconds, without its voltage dropping below 7.2 V - actually, according to the manufacturer, brand new, fully charged and cooled down to -40°F (-40°C) Odyssey 31M-PC2150 battery can provide 550 Amps for ~34 seconds.

Such cold temperature tolerances and performances mean that during the winter battery can be left on the boat, yacht, RV, or at any similar location without safety or reliability issues. If you do expect local temperatures to be lower than -40°F, it is recommended to remove the battery during such an extremely cold period and store it in the warm(er) area - important note for Alaska, Canada, or Siberia! :)

Odyssey 31M-PC2150 AGM as Deep Cycle Marine Battery

Although battery plates are relatively thin (to provide high currents), they are designed to withstand many charging-discharging cycles.

For example, the battery can withstand around 400 charge-discharge cycles down to 80% of maximum discharge (80% DoD - Depth of Discharge, 20% charge left).

However, avoiding really deep discharges can significantly prolong the battery's operating life, as shown in the following table:

Note: the battery is considered good as long as its native 20h capacity is more than 80% of the 20h capacity of the new battery. That means that when 31M-PC2150 battery 20h capacity drops down to 80 Ah or less, the battery is not considered to be good and should be properly recycled!

Although the nominal capacity of the battery is 100 Ah when the fully charged battery is being discharged down to 10.05 V (note: 10.05 V, not the 10.5 V) using constant current at 77°F (25°C), its capacity depends on the current and discharge time and are given in the following table:

Time	Watts (W)	Amps (A)	Capacity (Ah)	Energy (Wh)
2 min	7025	678.5	22.4	231.8
5 min	4740	438.5	36.4	393.4
10 min	3176	285.9	47.7	530.4
15 min	2428	215.5	53.9	607.0
20 min	1980	174.1	58.0	659.2
30 min	1460	127.0	63.5	730.0
45 min	1059	91.2	68.4	793.9
1 hr	835	71.5	71.5	835.2
2 hr	461	39.0	78.0	922.2
3 hr	322	27.1	81.4	966.8
4 hr	249	20.9	83.8	996.8
5 hr	204	17.1	85.6	1020.0
8 hr	134	11.2	89.7	1070.4
10 hr	110	9.2	91.9	1095.9
20 hr	60	5.0	100.3	1191.9

It is normal for all lead-acid batteries to lose capacity as they are being discharged using strong currents and Odyssey 31M-PC2150 is no exception. However, as the discharging current increases, its capacity drops, but it is still one of the best performers in its class.

If you have a 50-60 pounds electric trolling motor that draws some 50-60 Amps at maximum power, in the worst-case scenario, one can expect one hour of operation (plus some 10-15 minutes for safety). And since many fishermen don't use trolling motors at full power when fishing, one can expect 2-4 hours of operation on half a throttle of such electric trolling motor (time depends on the battery condition, weather conditions, actual trolling pace, etc).

When charging 31-PC2150 battery used for cycling applications, it is important to use battery chargers that can deliver at least 0.4C strong currents in the bulk charge mode and that can charge the battery up to 14.7 V.

Odyssey 31M-PC2150 vs. Other Group 31 Batteries

The following table lists the most popular BCI group 31 batteries, with their most important features:

Note: Amazon affiliate links in the table open in the new windows, feel free to check them out.

All of the batteries in the table are lead-acid AGM batteries except Battle Born 100Ah LiFePO4 deep cycle battery, which is an excellent deep cycle battery designed for various applications, except starting applications (it can deliver 100 Amps continuously, and 200 Amps for 30 seconds).

Also, it is a very lightweight battery, being almost 3x lighter than the Odyssey 31M-PC2150 battery. But, the Battle Born 100Ah LiFePO4 deep cycle battery is also a very expensive battery.

When 31-PC2150 batteries are compared with another group 31 AGM batteries, one can conclude:

- group 31 AGM batteries are heavy, and the 31-PC2150 is one of the heaviest in this class,

- high-quality deep cycle group 31 batteries have somewhat better 20h capacity and RC rating than the 31-PC2150 battery,

- common deep cycle group 31 AGM batteries have capacity and RC rating similar to the 31-PC2150 dual purpose battery.

- other dual-purpose group 31 AGM batteries are lighter and have a lower CCA/MCA rating than the 31-PC2150 battery.

Personally, in this group, only Exide XMC-31 comes close to the 31-PC2150 battery. However, also note that Exide XMC-31 is an almost 10 pounds lighter battery.

If you need a good 31 group AGM battery and don't have weight issues, go for the Odyssey 31M-PC2150 battery.

Odyssey 31M-PC2150 vs. Other 1000+ CCA Batteries

To be able to provide 1000+ CCAs is a very tough requirement for any type of marine or automotive battery.

Many batteries can provide 1000+ MCAs and especially 1000+ HCAs, but as the temperature drops, so do the cranking amps.

The following table lists marine/automotive batteries that are able to provide at least 800 CCAs:

Note: Amazon affiliate links in the table open in the new windows, feel free to check them for the latest offers. 

Large deep AGM deep cycle batteries with a capacity of 200+ Ah are generally able to provide 1000+ CCAs. They are large, heavy, and store plenty of energy and although designed for cycling applications, they are obviously strong enough even for 1000+ CCA applications.

On the other hand, dual-purpose batteries weighing 65 to 85 pounds are generally able to provide 1000 CCAs (or almost 1000 CCAs).

Odyssey PC2250 is clearly the winner in 1000+ CCAs dual-purpose battery class, at least regarding performances. However, it is also some 8 pounds heavier than the PC2150 battery and 18 pounds(!) heavier than Exide XMC-31.

Again, when looking for the 1000+ CCA battery, Odyssey 31M-PC2150 is perhaps the best-balanced battery.

For more about these batteries, check our Pick the Best 1000 CCA (Cold Cranking Amps) Marine Battery article.

How to Charge Odyssey 31-PC2150 Battery

When the Odyssey 31-PC2150 battery is part of an electric system that features an AGM battery charger, users should let that charger keep the battery fully charged - examples include alternators combined with charging controllers commonly found in automotive, marine, and light industrial applications.

However, when the battery is charged on its own, on the workbench, for example, it should be charged using a smart, microprocessor-controlled AGM battery charger with a temperature probe.

Before charging user should set the battery type (AGM), battery use (cycling, standby), and let the charger do the rest.

Since the Odyssey 31-PC2150 battery features 100Ah nominal capacity and that it accepts charge very well, battery chargers with a maximum current of 20 Amps can be used, although chargers in the 10-20 Amps range will be just fine.

The temperature probe is very important when the battery is being charged during cold or hot days - lead-acid batteries feature a negative temperature coefficient and when being charged in winter, charging voltage must be slightly increased, or the battery will not be fully recharged.

Also, when the lead-acid batteries are being charged during summer, the charging voltage must be slightly lower, or there is a risk of overcharging the battery.

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For Short: Odyssey 31M-PC2150 battery is not cheap and also not the lightest SLA AGM battery.

But, it is also one of the best-balanced designs, very reliable in broad temperature range, with excellent electrical characteristics. It is worth its price, IMHO of course.

For more reviews and recommendations, check Odyssey 31M-PC2150 Marine Dual Purpose Battery Amazon link (link opens in the new window).