Group 27 Batteries - Dimensions, Features, and Recommendations

Group 27 batteries are rather large and powerful batteries, featuring 20h capacity in 66-110 Ah range, providing 600-1000 CCA, 140-220 minutes RC, etc. Their weight depends on the internal construction, ranging between 54 and 70 pounds (24.5 - 32 kg).

Group 27 batteries' physical dimensions depend on the exact battery group because there are three different, although very similar battery groups: Group 27, Group 27F, and Group 27H, although they are often labeled as Group 27 Batteries.

Group 27 batteries are very common in automotive, marine, off-the-grid, RVs, and similar applications, making them one of the most popular battery groups.

Updated: January 6, 2024.

Group 27 Battery Dimensions

As said before, there are three sub-groups of group 27 batteries, and their actual dimensions are given in the following table:

BCI Group Size	L x W x H (mm)	L x W x H (inches)	Amazon Search
27	306 x 173 x 225	12 1/16 x 6 13/16 x 8 7/8	Group 27 Battery
27F	318 x 173 x 227	12 1/2 x 6 13/16 x 8 15/16	Group 27F Battery
27H	298 x 173 x 235	11 3/4 x 6 13/16 x 9 1/4	Group 27H Battery

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

The real-life difference among these batteries is very small, but sometimes even a few millimeters can decide if the battery can (or cannot) fit the battery compartment/tray.

When labeling their batteries, most manufacturers provide both actual dimensions (inches, millimeters) and BCI Group Size, so before buying a new battery, check the actual dimensions of your battery compartment - better safe than sorry :)

Group 27 Battery Features and Specifications

Generally, group 27 batteries feature physical dimensions of 12.0625 x 6.8125 x 8.875 inches (306 x 173 x 225 mm), and as such, they are slightly smaller than group 31 batteries.

Most group 27 batteries are Sealed Lead Acid (SLA) Absorbent Glass Mat (AGM) deep cycle batteries, although there are several very popular dual-purpose AGM group 27 batteries.

Lithium group 27 batteries are not as common as lithium group 31 batteries. Thus, if you are looking for a 12V 100Ah or similar Lithium Iron Phosphate (LiFePO₄) battery, check our Group 31 Batteries article.

Group 27 batteries, on average, feature a 20h capacity in 66-110 Ah range, 600-1000 CCA, 140-220 minutes RC, etc.

Their weight depends on the internal construction (flat plates, spiral wound plates) and ranges between 54 and 70 pounds (24.5 - 32 kg).

Most Popular Group 27 Batteries

The following table lists the most popular group 27 batteries, with their most important features:

Note: Amazon links in the table open in the new windows ('Model' column), so feel free to check them for the most up-to-date prices and offers.

There are other group 27 batteries on the market, but these are the most popular ones.

As one can see, almost all the batteries in the table are AGM (Absorbent Glass Mat), SLA (Sealed Lead Acid), and spill-proof batteries, being able to operate in virtually any position.

Lithium group 27 batteries (mostly LiFePO₄) are not so common due to their price, but they feature a good 20h capacity, a much larger number of charging/discharging cycles, and are much lighter than AGM SLA batteries.

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Optima Group 27 Batteries

Optima Group 27 batteries feature spiral-wound cells and are lighter than other AGM SLA batteries.

They also feature the smallest 20h capacity of 66 Ah (66 Ah vs. 92-110 Ah).

However, both D27M BlueTop and D27F YellowTop are very popular batteries due to their balanced design, vibration resilience, and durability.

Also, they feature 1000 MCA Amps value, which is ~18.5 Amps per pound (~40.8 Amps per kg), while NorthStar NSB-AGM27 features 1080 MCA Amps (~15.9 Amps per pound, ~34.8 Amps per kg).

Optima D27M BlueTop is intended for marine applications, while Optima D27 YellowTop is intended for automotive applications.

For more information about these batteries, check our Optima Batteries D27M BlueTop and D27F YellowTop Starting and Deep Cycle Batteries article, and for the most up-to-date offers and prices, follow Optima D27M BlueTop and Optima D27F YellowTop Amazon links (links open in the new windows).

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VMAXTANKS Group 27 Batteries

VMAXTANKS manufactures three batteries in this size:

• MR127-100 is a general AGM SLA group 27 battery with good deep discharge features. Also, it can be used as a starting battery, at least for smaller engines (MCA value of 800 Amps).
• SLR100 is a solar AGM SLA group 27 battery optimized for low-current applications - it should NOT be used as a starting battery. Although both MR127-100 and SLR100 feature the same 20h capacity (100 Ah), SLR100 features a better RC value (220 vs 200 minutes).
• XTR27-100 is a high-performance AGM SLA group 27 battery. It features 110 Ah 20h capacity, 220 minutes RC, and 880 MCA amps.

For more information about these batteries feel free to check our VMAXTANKS MR127-100 AGM Deep Cycle Battery article, and for the most up-to-date offers and prices, check VMAXTANKS MR127-100, VMAXTANKS SLR100, and VMAXTANKS XTR27-110 Amazon links (links open in the new windows).

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Universal Power Group UPG UB121000 AGM Deep Cycle Group 27 Battery

UPG UB121000 AGM is one of the most popular deep cycle group 27 batteries thanks to its performances and affordable price.

The battery cycles well, recovers well from deep discharges, accept charge well, and is commonly used as trolling motor battery, solar battery, off-the-grid battery, marine battery, RV battery, etc.

Note: this is not THE BEST deep cycle group 27 battery, but for its price, it has a lot of to offer - it is one of the best buy group 27 batteries.

The manufacturer also provides constant current and constant power discharge tables, allowing the users to actually see what their battery can do and what cannot:

Constant Current Discharge Table

Cell End Voltage (V)	Battery End Voltage (V)	5 min	10 min	15 min	30 min	1 hr	2 hr	3 hr	4 hr	5 hr	8 hr	10 hr	20 hr
1.6 V	9.60 V	351.5	256.5	180.5	109.3	57.0	33.3	24.4	19.0	15.7	11.0	10.0	5.4
1.7 V	10.20 V	309.7	233.7	161.5	103.6	53.6	31.7	23.8	18.5	15.4	10.8	9.7	5.3
1.75 V	10.50 V	298.3	222.3	152.0	100.7	52.3	31.0	23.2	18.2	15.2	10.7	9.5	5.2
1.8 V	10.80 V	286.9	210.9	142.5	97.9	50.4	30.2	22.6	18.0	14.8	10.5	~9.3	5.1
1.85 V	11.10 V	275.5	199.5	133.0	95.0	48.5	29.5	21.9	17.4	14.4	10.2	9.0	4.9

Note: The value for 10 hr current down to 10.80 V is given as an approximation because the official data given by UPG is - wrong.

Constant Power Discharge Table

Cell End Voltage (V)	Battery End Voltage (V)	5 min	10 min	15 min	30 min	1 hr	2 hr	3 hr	4 hr	5 hr	8 hr	10 hr	20 hr
1.6 V	9.60 V	3732.6	2818.7	1917.1	1160.0	660.3	384.8	283.1	220.4	181.5	128.3	115.9	62.4
1.7 V	10.20 V	3438.1	2594.5	1792.7	1149.5	620.4	367.7	275.5	214.7	~178	125.4	113.1	60.8
1.75 V	10.50 V	3383.0	2521.3	1723.3	1141.9	600.4	359.1	268.9	210.9	175.8	124.5	111.2	60.0
1.8 V	10.80 V	3339.3	2454.8	1658.7	1139.1	584.3	351.5	263.2	207.1	172.9	121.6	110.2	59.8
1.85 V	11.10 V	3278.5	2374.1	1582.7	1130.5	576.7	350.6	260.3	206.2	172.0	120.7	107.4	58.0

Note: Again, the value for 5 hr power down to 10.20 V is given as an approximation because the official data given by UPG is - wrong.

These values are given for a new, fully charged battery at room temperature.

For the most up-to-date offers and prices, feel free to check the UPG UB121000 Group 27 AGM Battery Amazon link (the link opens in the new window).

Of course, there are other rather popular group 27 batteries on the market as well, for example, Mighty Max ML100-12, NPP NP12-90Ah, etc.

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How to Charge Group 27 Batteries

To prolong their operating time, group 27 batteries should be charged with battery chargers optimized for their exact capacity, chemistry, and use.

For example, lithium group 27 batteries with an average capacity of ~100Ah should be charged with dedicated 25-30 Amps lithium battery chargers or advanced lead-acid battery chargers that feature dedicated lithium battery charging mode.

Lead-acid group 27 batteries should be recharged with 10-15 Amps advanced battery chargers that support charging modes like desulfation, cell equalization, maintenance mode, and similar. Also, temperature compensation is a must-have feature.

Note: some brands claim that their group 27 AGM batteries support charging currents up to 30 Amps. Personally, to prolong the battery lifetime, keep the charging current up to 0.2C - up to 20 Amps for a 100Ah lead-acid battery.

One of the most popular advanced battery chargers is a NOCO GENIUS10 Smart Battey Charger.

This is rather a versatile tool, not just a 12V battery charger - it may be used to charge 6V and 12V lead-acid batteries, 12V lithium batteries, may be used to (try to) repair 12V batteries, may be used as 12V power supply, supports battery maintenance mode, etc.

Despite not being the cheapest 10A 6V/12V battery charger on the market, it is one of the most popular ones.

For more information, feel free to follow NOCO Genius10 Smart Battery Charger Amazon link (the link opens in the new window).

However, no matter how good the NOCO Genius10 Smart Battery Charger is, it can be used to charge "only" one battery at a time. If you need to charge more than one battery, consider buying a multibank battery charger, for example, the NOCO Genius GENPRO 10x4 Smart Battery Charger.

NOCO Genius GENPRO 10x4 Smart Battery Charger is very similar to the NOCO Genius10 Smart Battery Charger, except that it can charge four (4) batteries at the same time with 10 Amps each (for a total of 40 Amps).

This is also anything but a cheap battery charger, but again, it is one of the most popular units in its class.

For more info, feel free to check the NOCO Genius GENPRO 10x4 Smart Battery Charger Amazon link (the link opens in the new window).

Are 10 Amps Enough?

If You want to increase the number of charging/discharging cycles of your lead-acid battery, you will not regularly discharge it below 80% DoD, preferably not below 50% DoD.

In such cases, 10 Amps battery chargers can charge:

• 80% DoD: 80Ah @10Amps → 9-10 hours to 100% SoC
• 50% DoD: 50Ah @10Amps → 5.5-6 hours 10 100% SoC

Again, if You are in a hurry, consider 20-25 Amps battery chargers if supported by the battery model that you have.

Group 27 Batteries as Trolling Motor Batteries

Group 27 batteries are regularly used as trolling motor batteries, providing currents up to 50-60 Amps.

If we check the constant current discharge table for the UPG UB121000 battery, we can see that such a battery can provide the following:

• 50.4A for 1h down to 1.8V/cell (10.8V battery): typically used in emergencies when the trolling motor is pushed to 100% throttle. Note: if your trolling motor is regularly used at 100% throttle, it is seriously underpowered.
• 30.2A for 2h down to 1.8V/cell (10.8V battery): typically used when quickly changing fishing location or similar.
• 22.6A for 3h down to 1.8V/cell (10.8V battery): just cruising around.

Of course, actual current consumption depends on the motor, boat, weather conditions, sea/water conditions, etc., but this list gives You a rough idea of what one 12V 100Ah lead-acid battery can do.

Note: in these examples, the battery was discharged down to 10.8V, not 10.5V. 10.8V is rather low discharge voltage, but it is not yet 100% DoD.

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Long Story Short: Group 27 batteries are capable of providing really strong currents that can cause damage, injuries, or worse. So, whatever you do, be sure to know what you are doing, or let certified professionals do it.

Note: Amazon links in the table open in the new windows ('Model' column), so feel free to check them for the most up-to-date prices and offers.

When looking for a proper battery group 27 replacement, check the actual size of the old battery and the battery compartment, check its capacity, CCA/MCA currents, RC values, and everything that may be important. The new battery should be at least equal (or better) in performance to the old battery and charged properly with the chargers at your disposal.