Best Group 24 Batteries

Group 24 batteries are medium-size lead-acid and lithium batteries commonly used in deep cycle applications, including automotive, marine, light-industrial, off-the-grid, medical, security, and other similar applications.

Group 24 batteries are rarely built as starting/cranking batteries, but dual-purpose group 24 batteries can crank surprisingly large gas and diesel engines.

Published: March 17, 2023.

Group 24 Batteries Features and Specifications

Group 24 batteries feature physical dimensions of (L x W x H) 10 1/4 x 6 13/16 x 8 7/8 inches (10.25 x 6.8125 x 8.875 inches, 260 x 173 x 225 mm), with the positive battery terminal generally on the left side when viewing the battery from the front.

However, one must be aware that group 24 batteries include several sub-models, each differing slightly in size from the main 'group 24 battery':

BCI Group Size	L (mm)	W (mm)	H (mm)	L (inches)	W (inches)	H (inches)
24	260	173	225	10 1/4	6 13/16	8 7/8
24F	273	173	229	10 3/4	6 13/16	9
24H	260	173	238	10 1/4	6 13/16	9 3/8
24R	260	173	229	10 1/4	6 13/16	9
24T	260	173	248	10 1/4	6 13/16	9 3/4

Note: group 24 batteries feature a positive battery terminal "generally" on the left side - we say "generally" because some submodels feature a positive battery terminal on the right side, for example, group 24R. Before buying a new battery, not just a group 24 battery, always check the actual size of your old battery, terminal type and orientation, and the size of the battery compartment.

Group 24 batteries are mostly AGM lead-acid batteries, with wet/flooded group 24 batteries being phased out.

Group 24 AGM Batteries

AGM group 24 batteries are spill-proof, maintenance-free batteries that can withstand many deep discharge cycles, although it is recommended not to discharge them below 50% DoD in order to prolong their operating life.

Although most AGM group 24 batteries are designed as deep cycle batteries, thanks to the AGM technology, they can also provide a few hundred Amps and can be used to crank smaller internal combustion engines occasionally. However, they are not designed nor intended for such use.

On average, group 24 AGM batteries feature a nominal voltage of 12V, a capacity of 75Ah, and an RC value of 140-180 minutes, and they weigh 45-55 pounds (20.4-25 kg).

Group 24 Lithium Batteries

Lithium group 24 batteries are not as common as AGM group 24 batteries, but they offer several advantages over lead-acid batteries, including:

• they support a much larger number of deep discharge cycles, very often 7-10x more.
• generally, they are 2-3x lighter than lead-acid batteries,
• as the discharge current is increased, the actual capacity of the lithium batteries doesn't decrease, at least not as nearly as the capacity of the lead-acid batteries,
• lithium batteries feature a very low self-discharge rate.

But lithium batteries also have some disadvantages:

• initially, they cost much more than lead-acid batteries, although in the long run, thanks to the lighter weight and a much larger number of charging/discharging cycles, they save money,
• Battery Management System (BMS) protects the lithium battery from unwanted events, but it can also cause issues with high-drain discharge applications,
• lithium batteries generally have to be recharged either using the car's electric system (alternator in combination with the car's charge controller) or using dedicated lithium battery chargers (or AGM battery charger with dedicated lithium battery charging mode). Smart AGM battery chargers, especially ones with desulfation mode, can damage the battery or force BMS to disconnect the battery.

BCI Group 24 lithium batteries should be used for applications where the mass of the battery is of great importance and for applications where batteries cycle a lot.

The following comparison chart lists some of the most popular group 24 batteries with their most important features and specifications:

Deep cycle AGM batteries should not be used as cranking batteries, but the dual-purpose NorthStar NSB-AGM24 is able to provide 840 CCA Amps, which is an excellent result for a dual-purpose battery with a nominal capacity of 76 Ah.

Deep cycle lithium batteries are protected with the built-in BMSs and usually can provide 1C currents continuously and ~2C for a very short period of time - exact values differ from the battery model to the battery model and must be checked for each battery.

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Long Story Short: BCI Group 24 batteries are tough and durable batteries, well suited for applications that require reliable power sources that can also cycle very often.

As for cranking/starting batteries, BCI Group 24 batteries are not well suited - dual-purpose models can provide strong currents and can be used as cranking/starting batteries, but most of these batteries such use will shorten their operating life significantly.

Lithium group 24 batteries offer great weight savings and a huge number of charging and discharging cycles (2000+ cycles down to 100% DoD), but they cost more than lead-acid batteries. But, in the long run, they actually save money.