Group 24 AGM Deep Cycle Battery Guide: Compact 12V Marine Power

Short answer: A Group 24 AGM deep cycle battery like the Pro-Guide 24AGM (PGM24AGM) is a sealed, maintenance-free 12V absorbed glass mat battery in the compact Group 24 case (about 10.25 x 6.7 x 8.2 in). It is rated for 150 minutes of reserve capacity at 25 amps, 83Ah at the 20-hour rate, 525 CCA and 635 MCA, which makes it the smallest and lightest of Pro-Guide's AGM marine batteries and a strong fit for electronics, small boats and space-limited compartments.

Not every boat has room for a big Group 31, and not every job needs one. If you are powering a bank of graphs, a small trolling motor or a tight compartment in a jon boat or bay boat, the Group 24 size is often the sweet spot. This guide explains what a Group 24 AGM deep cycle battery is, how long it runs common marine loads, how AGM compares with flooded lead-acid and lithium, how to charge it correctly and how to choose between the 24AGM and its bigger siblings.

Key Takeaways

• Compact Group 24 case: 10.25 x 6.7 x 8.2 in (260 x 169 x 208 mm), the smallest of Pro-Guide's three AGM marine sizes.
• Real deep cycle capacity: 150 minutes of reserve capacity at 25A and 83Ah at the 20-hour rate, according to the Pro-Guide 24AGM data sheet.
• Cranking power too: 525 cold cranking amps (CCA) and 635 marine cranking amps (MCA), printed right on the label.
• Sealed and maintenance-free: a valve-regulated lead-acid (VRLA) AGM design, so there is no water to add and no acid to check.
• Backed by a 2-year free replacement warranty (24 months).

What Is a Group 24 AGM Deep Cycle Battery?

The term combines three separate ideas, and it helps to pull them apart:

• Group 24 is a case-size standard from the Battery Council International (BCI). It tells you the approximate outside dimensions, so the battery fits Group 24 boxes, trays and hold-downs. It says nothing about the chemistry or capacity inside.
• AGM stands for absorbed glass mat. The electrolyte is held in fiberglass mats packed between the lead plates instead of sloshing around as free liquid. That is why AGM batteries are sealed, spill-resistant and do not need watering.
• Deep cycle means the battery is built to deliver steady current for hours and then be recharged, over and over, rather than delivering a single short burst like a pure starting battery.

The Pro-Guide 24AGM checks all three boxes. Its data sheet describes a deep cycle design that uses a patented nano-structural carbon additive in the negative plate, which Pro-Guide says lets the battery charge up to 25% faster than conventional deep cycle batteries, deliver 100% of rated capacity out of the box and better resist the damage that comes from over-discharge and partial-state-of-charge use. In plain English: it is designed for the way anglers actually use batteries, which is rarely a perfect full charge followed by a perfect full discharge.

Unlike many pure deep cycle batteries, the 24AGM also carries real cranking ratings: 525 CCA and 635 MCA. Pro-Guide's product description refers to the AGM line as dual purpose, so the 24AGM can handle smaller engine starting jobs as well as accessory loads.

Pro-Guide 24AGM Specifications

Model / SKU	Pro-Guide 24AGM (PGM24AGM)
Chemistry	AGM (absorbed glass mat), valve-regulated lead-acid (VRLA)
BCI group size	24
Voltage	12V (6 cells)
Capacity	83Ah at the 20-hour rate (80Ah at 10 hours, 72Ah at 5 hours, 63Ah at 3 hours)
Reserve capacity	150 minutes at 25A
Cold cranking amps	525 CCA
Marine cranking amps	635 MCA
Charge current	10A standard / 15A maximum
Cycle charge voltage	14.6V to 14.8V at 77°F
Float voltage	13.6V to 13.8V at 77°F
Operating temperature	Discharge -4°F to 140°F; charge 0°F to 122°F
Terminals	1 SAE post, 1 stud terminal
Dimensions	10 1/4 x 6 7/10 x 8 1/5 in (260 x 169 x 208 mm)
Weight	42 lb (19.1 kg)
Warranty	24-month free replacement

Want every chart and curve? Download the 24AGM data sheet (PDF).

The 24AGM label prints its key ratings: 635 MCA, 525 CCA and 150 minutes of reserve capacity. Terminal covers come on both posts.

How Long Will a Group 24 AGM Battery Run Your Electronics?

For lead-acid batteries, including AGM, plan on using only about 50% of rated capacity on a regular basis. Pulling a lead-acid battery deeper than that is possible, but doing it every trip shortens its life. So for rough planning, treat the 24AGM's 83Ah (20-hour rate) as about 41Ah of everyday usable energy.

Two numbers on the spec sheet help you estimate runtime:

• Amp-hours (Ah): best for light, steady loads like fish finders. Divide usable Ah by the load in amps.
• Reserve capacity (RC): the number of minutes a fully charged battery can deliver 25A before it is completely flat. The 24AGM is rated at 150 minutes. It is the more realistic number for heavier loads, because lead-acid batteries deliver fewer amp-hours as the current goes up.

Load	Typical draw	Rough runtime to ~50% on the 24AGM
Single fish finder or chartplotter	About 2A	About 20 hours
Two graphs plus a transducer	About 5A	About 8 hours
Multiple graphs plus live sonar	About 10A	About 4 hours
12V trolling motor, moderate speed	About 25A	About 75 minutes (half of the 150-minute RC)

These are estimates, not promises. Temperature, battery age, how hard you run the load and how fully you charged the night before all change the result. Notice how quickly a 12V trolling motor eats into a single Group 24: that is why most anglers either use the 24AGM for electronics and accessories, or run several of them together for a 24V or 36V trolling motor system.

That second approach works well in practice. One customer runs three 24AGM batteries in a Triton bass boat. He reports pulling about 180 pounds out of the boat compared with his old setup, gaining room in the compartment and running his trolling motor for three days in the current of the Coosa River without recharging. He also noticed a better hole shot and top end from the weight savings.

AGM vs. Flooded Lead-Acid vs. Lithium in a Group 24 Case

All three chemistries come in Group 24 cases. Here is how they typically compare, using the 24AGM's published numbers for the AGM column.

Factor	Flooded lead-acid	Pro-Guide 24AGM	Group 24 LiFePO4 lithium
Maintenance	Check and top off water	None; sealed VRLA	None
Spill risk	Free liquid acid can spill	Electrolyte held in glass mats; spill-resistant	No liquid acid
Usable capacity	About 50% of rating	About 50% of 83Ah, roughly 41Ah	Nearly all of the rated Ah
Engine cranking	Varies by model	525 CCA / 635 MCA	Deep cycle lithium models are usually not for starting
Weight	Heavy	42 lb	Typically about half of a lead-acid battery
Charger	Flooded profile	AGM profile	Lithium (LiFePO4) profile
Up-front cost	Lowest	Moderate	Highest

AGM sits in the middle. Compared with flooded batteries, it removes the watering chore and the spill risk, and it typically handles vibration and pounding better because the plates are tightly packed. Compared with lithium, it costs less up front, uses chargers many boats already have and can also start an engine. Lithium wins on weight, usable capacity and cycle life. If you are leaning toward lithium, read our Group 24 lithium battery guide or browse deep cycle lithium batteries.

What Is the 24AGM Best For?

The 24AGM earns its place where space, weight and simplicity matter more than maximum capacity:

• Dedicated electronics battery: isolating your graphs and sonar on their own battery keeps their voltage clean and stops trolling motor draw from causing resets. A Group 24 is usually plenty for this job. Learn why in Should You Run a Separate Battery for Your Boat Electronics? and wire it with a kit like The Bass Tank Power Harness.
• Multi-battery trolling motor banks: two 12V batteries in series make 24V, and three make 36V. Using identical batteries of the same age is important. See One Pack or Three? Choosing the Right Trolling Motor Battery Setup.
• Small boats and tight compartments: jon boats, small center consoles and older bass boats with Group 24 trays.
• Smaller outboard starting: with 525 CCA and 635 MCA, it can serve as a starting or dual purpose battery where your engine's cranking requirement fits. Check your owner's manual for the minimum.

The 24AGM's compact Group 24 footprint leaves more room in the compartment for wiring, chargers and gear.

How to Charge a Group 24 AGM Battery

AGM batteries are sensitive to charging voltage, so the right profile matters more than raw charger size. Follow the numbers from the 24AGM data sheet and specifications:

1. Use an AGM charging profile. For cycle use, the data sheet calls for 14.6V to 14.8V at 77°F. For float or maintenance charging, it calls for 13.6V to 13.8V. A lithium-only profile is not appropriate for AGM.
2. Stay within the charge current. Pro-Guide lists 10A as the standard charge current and 15A as the maximum for the 24AGM. A 10A-per-bank onboard charger matches the standard rate.
3. Adjust for temperature. The data sheet lists temperature compensation of about -4mV per °F per cell for cycle charging (-3mV for float). In plain terms, charge voltage should come down in hot weather and go up in cold weather. Many smart chargers do this automatically with a temperature sensor.
4. Charge between 0°F and 122°F. The battery can discharge from -4°F to 140°F.
5. Recharge promptly. Leaving any lead-acid battery partially discharged for days invites sulfation. Plug in after every trip.

How long does it take? As a rough estimate, divide the amp-hours you used by the charger's output, then add time for the slower final (absorption) stage. Replacing about 41Ah with a 10A charger takes roughly 4 to 5 hours of bulk charging, plus a few hours of topping off.

Good charger matches include the 12V 10A 1-Bank Battery Charger for a single electronics battery, the 12V 10A 2-Bank Battery Charger for a 24V bank and the 12V 10A 3-Bank Battery Charger for a 36V bank. Set any charger to its AGM mode if it has one. For a 12V trolling motor, the 12 Volt Trolling Motor Kit with On-Board Charging Connection Kit keeps wiring tidy.

Install and Maintenance Tips

Charge it before first use

The data sheet advises charging the battery before using it. A full charge before your first trip gives you a known starting point.

Secure it in a box or tray

Even a sealed AGM battery should be strapped down. The NOCO Group 24 Snap-Top Battery Box and NOCO Group 24 Battery Tray are sized for Group 24 batteries. Before ordering, measure your compartment: the 24AGM is about 10.25 in long, 6.7 in wide and 8.2 in tall.

Keep terminals clean and tight

Loose or corroded connections cause voltage drop that looks like a weak battery. A light coat of battery corrosion preventative spray helps in humid, salty environments.

Store it charged

Self-discharge is less than 3% per month at 77°F, according to the data sheet, and Pro-Guide recommends recharging after up to 6 months in storage. For winter layup, charge fully, disconnect loads and top it off before spring, or leave it on a maintainer with a float voltage around 13.6V to 13.8V.

For more habits that extend battery life, see our marine battery maintenance guide.

24AGM vs. 27AGM vs. 31AGM: Which Size Do You Need?

Pro-Guide builds the AGM line in three sizes. The right choice depends on your compartment and your biggest load.

Model	Reserve capacity	CCA / MCA	Size (L x W x H)	Weight
24AGM	150 min	525 / 635	10 1/4 x 6 7/10 x 8 1/5 in	42 lb
27AGM	175 min	600 / 750	12 x 6 3/5 x 8 1/5 in	50 lb
31AGM	205 min	800 / 1,000	13 x 6 4/5 x 8 1/2 in	72.75 lb

Choose the 24AGM if your tray is Group 24, if the battery mostly runs electronics, or if you are building a multi-battery bank where every pound adds up. Step up to the 27AGM if your 12V trolling motor is the main load and you have the length for it. Choose the 31AGM when you need the most capacity and cranking power in one battery, such as a larger outboard or a house bank.

Frequently Asked Questions

How many amp-hours is a Group 24 AGM deep cycle battery?

It varies by brand. The Pro-Guide 24AGM is rated at 83Ah at the 20-hour rate and 150 minutes of reserve capacity at 25A. Plan on using about half of that, roughly 41Ah, for long battery life.

Can a Group 24 AGM battery start a boat engine?

Yes, if your engine's requirement fits. The Pro-Guide 24AGM is rated at 525 CCA and 635 MCA. Check your outboard's owner's manual for its minimum cranking rating.

Is the Pro-Guide 24AGM maintenance-free?

Yes. It is a sealed, valve-regulated AGM battery, so there is no water to add. Keep it charged, keep the terminals clean and secure it in a box or tray.

What charger do I need for a 12V AGM battery?

Use a charger with an AGM profile. The 24AGM data sheet calls for 14.6V to 14.8V for cycle charging and 13.6V to 13.8V for float at 77°F, with a 10A standard and 15A maximum charge current.

How long will a Group 24 AGM battery run a fish finder?

At about 2A, the Pro-Guide 24AGM can run a single fish finder for roughly 20 hours before reaching 50% charge. Larger graph and sonar setups drawing about 10A get roughly 4 hours.

Is a Group 24 AGM the same size as a Group 24 lithium battery?

Both follow the Group 24 size standard and fit Group 24 boxes and trays, but exact height varies by model. The Pro-Guide 24AGM measures about 10.25 x 6.7 x 8.2 in, so confirm height and terminal clearance before switching.

How long is the warranty on the Pro-Guide 24AGM?

The Pro-Guide 24AGM includes a 24-month free replacement warranty.

Get Compact AGM Power for Your Boat

If your boat has a Group 24 slot, or you want a sealed, maintenance-free battery for electronics or a multi-battery trolling motor bank, the Pro-Guide 24AGM delivers 150 minutes of reserve capacity, 525 CCA and a 2-year free replacement warranty in the most compact case of our AGM line. It is field-tested by professional anglers and backed by a team that will help you size the right setup.

SHOP THE PRO-GUIDE 24AGM

Not sure which battery or charger fits your rig? Call our team at 1-800-827-3232 or browse all AGM batteries and battery chargers.

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