1-800-827-3232
Group 24 Dual Purpose Marine Battery Guide: Pro-Guide 24M500
Short answer: A Group 24 dual purpose marine battery like the Pro-Guide 24M500 is a 12V flooded lead-acid battery that handles both jobs on a small boat: it delivers 500 cold cranking amps (CCA) and 625 marine cranking amps (MCA) to start your outboard, plus 95 minutes of reserve capacity (RC) at 25 amps to run a fish finder, bilge pump and lights. At 36.4 lb in a standard Group 24 case, it is the lightest and most affordable flooded dual purpose battery in the Pro-Guide lineup.
If your jon boat, aluminum fishing boat or small center console only has room for one battery, that battery has to start the motor and power everything else. This guide explains what a Group 24 dual purpose battery is, what the 24M500's ratings mean in real use, how long it can run your electronics, how flooded compares with AGM and lithium, and how to charge and maintain it so it lasts season after season.
Key Takeaways
- Two jobs, one battery: the 24M500 is labeled Dual Purpose, so it starts your engine and runs light accessory loads.
- Cranking power: 500 CCA, 625 MCA and 625 CA.
- Reserve capacity: 95 minutes at 25 amps, enough to keep basic electronics and a bilge pump going if the engine stops charging.
- Standard Group 24 case: 10 1/4 x 6 13/16 x 8 7/8 in and 36.4 lb (16.5 kg), so it fits common Group 24 boxes and trays.
- Warranty: 12 months free replacement and 30 months total pro-rata coverage.
What Is a Group 24 Dual Purpose Marine Battery?
"Group 24" is a case-size standard from the Battery Council International (BCI). It tells you the outside dimensions of the battery, not its chemistry or ratings. Group 24 is one of the most common marine battery sizes, which is why so many boats leave the factory with Group 24 trays, boxes and hold-downs.
"Dual purpose" describes the job. Marine batteries generally fall into three camps:
- Starting (cranking) batteries deliver a big burst of current for a few seconds to turn over an engine.
- Deep cycle batteries deliver steady, lower current for hours, for trolling motors and electronics.
- Dual purpose batteries split the difference: enough cranking amps to start a typical outboard, plus enough reserve capacity to run accessories between charges.
The Pro-Guide 24M500 is a flooded (wet cell) lead-acid dual purpose battery. Flooded batteries are the traditional, proven marine design. They are typically the lowest-cost way to get reliable starting power, and they reward a little routine maintenance with a long service life.
Pro-Guide 24M500 Specifications
| Model / SKU | Pro-Guide 24M500 (PGM24M500) |
| Type | Flooded lead-acid, dual purpose |
| Voltage | 12V |
| BCI group size | 24 |
| Cold cranking amps (CCA) | 500 |
| Marine cranking amps (MCA) | 625 |
| Cranking amps (CA) | 625 |
| Reserve capacity (RC) | 95 minutes at 25 amps |
| Charge current | 10A standard, 15A maximum |
| Terminals | 1 SAE post, 1 stud terminal |
| Dimensions | 10 1/4 x 6 13/16 x 8 7/8 in (260.3 x 174.6 x 228.6 mm) |
| Weight | 36.4 lb (16.5 kg) |
| Warranty | 12 months free replacement, 30 months total pro-rata |
Want the full sheet? Download the 24M500 data sheet (PDF). It also lists a height of 9 1/2 in to the top of the terminals, which is the number to check against your compartment lid.
The 24M500 prints its key ratings right on the label: 625 MCA, 500 CCA and 95 minutes of reserve capacity.
What Do 500 CCA, 625 MCA and 95 RC Mean?
Battery labels are full of acronyms. Here is what each rating on the 24M500 tells you:
Cold cranking amps (CCA): 500
CCA is the current a battery can deliver for 30 seconds at 0°F while holding a usable voltage. It is the toughest test because cold thickens engine oil and slows the battery's chemistry. If you launch early in spring or late in fall, CCA is the number that matters most.
Marine cranking amps (MCA): 625
MCA measures the same thing at 32°F, which better reflects typical boating conditions. That is why MCA is always higher than CCA. Most outboard manufacturers list a minimum MCA or CCA in the owner's manual. Match or exceed it.
Reserve capacity (RC): 95 minutes
RC is how many minutes a fully charged battery can supply 25 amps before dropping to 10.5 volts. It is the best single number for comparing how long a starting or dual purpose battery can run accessories. Do the math and 95 minutes at 25A works out to roughly 40 amp-hours delivered at that rate.
Put together, the 24M500's ratings make it a good match for small and mid-size outboards, with enough reserve to keep the essentials running when the engine is off.
How Long Will the 24M500 Run Your Electronics?
Because the 24M500 also has to start your engine, you should never run it flat. A good rule for any lead-acid battery is to use only about half of its capacity before recharging. Using the RC math above (roughly 40 amp-hours at a 25A draw), that leaves about 20 amp-hours for accessories. Here are rough estimates:
| Load | Typical draw | Rough runtime to about 50% |
| Single fish finder | About 1.5A | About 13 hours |
| Fish finder plus nav lights | About 3A | About 6 to 7 hours |
| Bilge pump running | About 5A | About 4 hours |
| Aerator / livewell pump plus electronics | About 8A | About 2.5 hours |
These are estimates, not guarantees. Lead-acid batteries usually deliver a bit more total capacity at low draws than the RC test suggests, and less in cold weather or as the battery ages. If you regularly run electronics for a full day with the motor off, or you run a trolling motor, add a dedicated deep cycle battery such as the Pro-Guide 24M140 Group 24 flooded deep cycle. Our guide Should You Run a Separate Battery for Your Boat Electronics? walks through the options.
Flooded vs. AGM vs. Lithium in a Group 24 Slot
Group 24 batteries come in three chemistries. Here is how they typically compare for a dual purpose job:
| Factor | Flooded (Pro-Guide 24M500) | Typical AGM | Typical lithium (LiFePO4) |
| Up-front cost | Lowest | Higher | Highest |
| Maintenance | Periodic water and terminal checks | Sealed, no watering | Sealed, no watering |
| Usable capacity | About 50% of rated | About 50% of rated | Most of rated capacity |
| Mounting | Upright only, vented location | Sealed, more mounting flexibility | Sealed, more mounting flexibility |
| Charging | Standard flooded profile | AGM profile | Lithium profile required |
| Weight | 36.4 lb | Usually similar or heavier | Usually much lighter |
For a boat that is used on weekends and lives on a trailer or a lift with a charger, flooded is typically the best value. If you cannot easily reach the battery to check water, AGM may be worth the premium. And if weight and deep cycling matter most, browse our dual purpose lithium batteries or read our Group 24 lithium battery guide.
What Is the 24M500 Best For?
The 24M500 is built for boaters who need dependable starts and modest accessory power without paying for capacity they will never use:
- Jon boats and small aluminum fishing boats: one battery that starts a smaller outboard and runs a fish finder, nav lights and a bilge pump.
- Single-battery boats with a Group 24 tray: it drops into the existing space with no modifications.
- Budget-friendly replacement: at 36.4 lb, it is the lightest flooded dual purpose model we offer, which makes it easier to swap and to carry to the charger.
- Starting battery in a multi-battery boat: pair it with a deep cycle trolling motor bank. See One Pack or Three? Choosing the Right Trolling Motor Battery Setup.
It is not the right choice if your outboard calls for more cranking amps than 500 CCA / 625 MCA, or if you need to run electronics all day with the engine off. For those boats, step up to the Pro-Guide 24M800 or a larger Group 31 31M225.
The built-in strap handle makes the 24M500 easy to lift in and out of the boat for charging or winter storage.
How to Charge a Flooded Dual Purpose Battery
Pro-Guide rates the 24M500 for a 10-amp standard charge and a 15-amp maximum. Staying at or below those numbers keeps heat and gassing under control and helps the battery reach its full life.
- Use a marine charger with a flooded (wet) lead-acid setting. Smart chargers taper current as the battery fills and switch to a float or maintenance mode.
- Match the charger to the rating. The Pro-Guide 12V 10A 1-Bank Battery Charger lines up with the 24M500's 10A standard charge rate. If the boat also has trolling motor batteries, a multi-bank charger such as the 12V 10A 2-Bank or 12V 10A 3-Bank charges every battery at once.
- Recharge soon after every trip. Lead-acid batteries left partially discharged build up sulfate on the plates, which slowly reduces capacity.
- Charge in a ventilated space. Flooded batteries typically release small amounts of hydrogen near the end of a charge, so keep sparks and flames away.
As a rough estimate, putting back 20 amp-hours with a 10A charger takes about two to three hours, allowing for normal charging losses and the slower final stage.
Installation and Maintenance Tips
Mount it upright and secure
Flooded batteries must stay upright. Strap the 24M500 into a box or tray so it cannot shift in rough water. The NOCO Group 24 Snap-Top Battery Box and NOCO Group 24 Battery Tray are sized for it.
Check the water level
On flooded batteries, the electrolyte level typically drops over time, especially in hot weather or with heavy charging. Every month or so during the season, check that the plates are covered. If they are not, top up with distilled water only, ideally after charging, and do not overfill. Always wear eye protection when you open the caps.
Keep the terminals clean
Corrosion on the posts adds resistance and can cause slow, weak starts. Clean the terminals, tighten the connections and protect them with battery corrosion preventative spray.
Store it charged
Before winter storage, fully charge the battery, disconnect it and keep it on a maintainer or recharge it every few weeks. A discharged lead-acid battery can freeze and crack in cold weather. Our marine battery maintenance guide covers the full off-season routine.
Carry a backup
A compact jump starter like our 12V 1000A Jump Starter is cheap insurance if you accidentally leave the electronics on overnight.
24M500 vs. 24M800: Which Should You Choose?
Both are 12V flooded Pro-Guide batteries in the same Group 24 case (10 1/4 x 6 13/16 x 8 7/8 in) with the same 10A / 15A charge rating and 1 SAE post, 1 stud terminal layout. The differences are power and weight:
| Spec | 24M500 | 24M800 |
| CCA / MCA | 500 / 625 | 800 / 1,000 |
| Reserve capacity | 95 minutes | 135 minutes (per product description and label) |
| Weight | 36.4 lb | 42 lb |
Choose the 24M500 if your outboard's cranking requirement is within 500 CCA / 625 MCA and you mainly need a reliable starter that also runs light accessories. Choose the 24M800 if you run a larger outboard, launch in cold weather or want more reserve capacity in the same footprint.
Frequently Asked Questions
What is a Group 24 dual purpose marine battery?
It is a 12V battery in the BCI Group 24 case size that can both start an engine and power accessories. The Pro-Guide 24M500 delivers 500 CCA, 625 MCA and 95 minutes of reserve capacity.
Can the 24M500 start my outboard?
Yes, as long as your engine's cranking requirement is within 500 CCA / 625 MCA. Check the minimum cranking rating in your outboard owner's manual.
Can I use the 24M500 for a trolling motor?
It can handle light, occasional trolling, but repeated deep discharges shorten the life of a dual purpose battery. For regular trolling, use a dedicated deep cycle battery bank.
How long will a Group 24 dual purpose battery run a fish finder?
As a rough estimate, the 24M500 can run a single fish finder drawing about 1.5A for around 13 hours before reaching about 50% charge, based on its 95-minute reserve capacity.
Does a flooded marine battery need maintenance?
Yes. Check the electrolyte level periodically and top up with distilled water if the plates are exposed, keep the terminals clean and tight, and recharge after every trip.
What charger should I use for the 24M500?
Use a marine charger with a flooded lead-acid setting at 10A standard and no more than 15A. The Pro-Guide 12V 10A 1-Bank Battery Charger is a good match.
How much does the 24M500 weigh?
The Pro-Guide 24M500 weighs 36.4 lb (16.5 kg), the lightest of our flooded dual purpose batteries.
What warranty comes with the 24M500?
It carries a 12-month free replacement warranty and 30 months of total pro-rata coverage.
Get the Pro-Guide 24M500
If your boat has a Group 24 tray and needs one dependable battery to start the motor and keep the electronics, lights and bilge running, the Pro-Guide 24M500 is a smart, budget-friendly choice. It gives you 500 CCA, 625 MCA and 95 minutes of reserve capacity in a 36.4 lb flooded case, backed by a 12-month free replacement warranty. The Pro-Guide 24M500 is sold through our dealer network, so call us at 1-800-827-3232 and we will point you to the closest dealer.
Not sure which battery your engine needs? Call our team at 1-800-827-3232 or browse all lead-acid batteries and battery chargers.
Built for the Water. Powered by Pro-Guide.
