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Group 24 Lithium Battery Guide: 12V 100Ah LiFePO4 Power in a Smaller Case
Short answer: A Group 24 lithium battery like the Pro-Guide 24M100 is a 12.8V, 100Ah LiFePO4 deep cycle battery that stores 1,280 watt-hours in a standard Group 24 case (10.25 x 6.83 x 9.19 in) and weighs just 23.8 lb. That means you get full 100Ah lithium performance in a footprint smaller than a Group 31, with more than 3,000 cycles at 100% depth of discharge and a 10-year warranty.
If you have ever opened a battery compartment and realized a Group 31 simply will not fit, this guide is for you. Below we cover what a Group 24 lithium battery is, how long a 12V 100Ah LiFePO4 battery runs your trolling motor and electronics, how it compares with AGM and lead-acid, how to charge it, and the setup tips our customers wish they had known on day one.
Key Takeaways
- Same power, smaller box: the 24M100 packs 100Ah and 1,280Wh into a Group 24 case, so it fits boats, kayaks, RVs and solar setups where a Group 31 won't.
- Light: 23.8 lb (10.8 kg), roughly half the weight of a typical Group 24 AGM.
- Long life: more than 3,000 cycles at 100% depth of discharge and more than 6,000 cycles at 80%.
- Built for the water: IP67 rated, Grade A cells anchored in epoxy, built-in battery management system (BMS).
- Backed for a decade: 5-year free replacement and 10-year pro-rata warranty.
What Is a Group 24 Lithium Battery?
"Group 24" is a size standard set by the Battery Council International (BCI). It describes the outside dimensions of the case, not the chemistry or capacity inside. Group 24 is one of the most common marine and RV battery sizes, which is why so many boats ship with Group 24 battery boxes, trays and hold-downs from the factory.
Traditionally, a Group 24 slot meant a flooded lead-acid or AGM battery with somewhere around 70 to 85 amp-hours of rated capacity, of which you could comfortably use only about half. A Group 24 lithium battery keeps the same footprint but swaps the lead plates for lithium iron phosphate (LiFePO4) cells. The result is more usable energy, a fraction of the weight and many times the cycle life, without cutting or rebuilding your battery compartment.
The Pro-Guide 24M100 is our 12V 100Ah LiFePO4 deep cycle battery in that Group 24 case. It delivers the same performance as the Pro-Guide 31M100, just in the smaller size that more compartments can accept.
Pro-Guide 24M100 Specifications
| Model / SKU | Pro-Guide 24M100 (PGL24M100) |
| Chemistry | Lithium iron phosphate (LiFePO4), Grade A cells |
| Nominal voltage | 12.8V |
| Capacity / energy | 100Ah / 1,280Wh |
| Cycle life | 3,000+ cycles at 100% DoD, 6,000+ at 80% DoD |
| Continuous discharge | 100A |
| Charge current | 20A standard, 50A maximum continuous |
| Charge cut-off voltage | 14.6V |
| Charging temperature | 14°F to 113°F (-10°C to 45°C) |
| Discharge temperature | -4°F to 140°F (-20°C to 60°C) |
| Protection | IP67, built-in BMS, epoxy-anchored cells, Pro-Boost recovery |
| Terminals | 1 SAE post, 1 stud terminal |
| Dimensions | 10.25 x 6.83 x 9.19 in (260.4 x 173 x 233.4 mm) |
| Weight | 23.8 lb (10.8 kg) |
| Warranty | 5-year free replacement, 10-year pro-rata |
Want the full numbers? Download the 24M100 data sheet (PDF).
The 24M100 drops into a standard Group 24 compartment. At 23.8 lb, most anglers can lift it in with one hand.
How Long Will a 12V 100Ah Lithium Battery Run?
For a quick estimate, divide the battery's 100Ah capacity by your load in amps. Because a LiFePO4 battery can use nearly all of its rated capacity and holds a steady voltage as it drains, the math is much closer to real life than it is with lead-acid.
| Load | Typical draw | Estimated runtime on the 24M100 |
| Single fish finder / chartplotter | About 2A | About 50 hours |
| Multiple graphs plus live sonar | About 10A | About 10 hours |
| 12V trolling motor, moderate speed | About 30A | About 3 hours |
Real runtime depends on the load, water and wind conditions, temperature and how far you discharge the battery. One customer reported running a trolling motor and two electronics units for four hours straight, then kept a second fish finder going for several more hours after the wind picked up. Another runs a Garmin 106SP and black box off a single 24M100 with capacity to spare.
Group 24 Lithium vs. AGM and Lead-Acid
If you are weighing a lithium upgrade against a new AGM, here is how the chemistries compare in the same Group 24 size.
| Factor | Pro-Guide 24M100 (LiFePO4) | Typical Group 24 AGM / lead-acid |
| Usable capacity | Nearly all of 100Ah | About 50% of rated capacity to protect battery life |
| Weight | 23.8 lb | Often 45 to 55 lb |
| Cycle life | 3,000+ at 100% DoD | Typically a few hundred cycles |
| Voltage under load | Stays flat until nearly empty | Sags steadily as it discharges |
| Maintenance | None; no watering, no equalizing | Periodic checks; flooded types need water |
| Warranty | 10 years (5 free replacement) | Usually 1 to 3 years |
The flat voltage curve matters more than most people expect. As a lead-acid battery drains, its voltage falls, and trolling motors slow down while electronics can reset or throw low-voltage alarms. A LiFePO4 battery holds its voltage under load, so your trolling motor and graphs perform the same at 3 p.m. as they did at launch. Add the weight savings and the thousands of extra cycles, and lithium usually costs less per cycle over the life of the battery even though it costs more up front.
What Is the 24M100 Best For?
The 24M100 is a deep cycle battery, built to deliver steady power for hours. It is not designed for engine starting. Here is where it shines:
- Dedicated electronics battery: isolating your graphs and live sonar on their own battery keeps voltage clean and steady for long tournament days. Read more in Should You Run a Separate Battery for Your Boat Electronics?
- Trolling motors: one 24M100 powers a 12V motor, two in series build a 24V 100Ah system, and three in series build a 36V 100Ah system. Pro-Guide rates the 24M100 for up to four batteries in series or parallel. See One Pack or Three? Choosing the Right Trolling Motor Battery Setup.
- Kayaks and small boats: where every pound and every inch counts, the Group 24 size and 23.8 lb weight make a big difference.
- RV house power and solar storage: 1,280Wh of usable energy for lights, fans, pumps and devices, with a cycle life suited to daily solar charging.
Compact enough for a fishing kayak, with the capacity to run a full Garmin electronics setup all day.
How to Charge a Group 24 LiFePO4 Battery
Charge time is roughly the capacity divided by the charger's output current:
- 20A standard charge: about 5 hours from empty.
- 30A charger: about 3.5 hours from empty, using a charger like the Pro-Guide 12V 30A Lithium Battery Charger.
- 50A maximum continuous: about 2 hours from empty.
A few rules keep your battery healthy for its full 3,000+ cycles:
- Use a lithium (LiFePO4) charging profile with a charge voltage between 14V and 15V and a 14.6V cut-off. Do not exceed 15V.
- Avoid chargers with an automatic "desulfation" mode. That mode is meant for lead-acid batteries and is not appropriate for lithium.
- Charge within 14°F to 113°F. The 24M100 can discharge down to -4°F, so it can power equipment on cold mornings, but wait for warmer conditions to charge.
- Don't drain it below 12V. According to the battery label, the 24M100 reads about 13.4V when fully charged and about 12.9V at 20% state of charge. Let it rest one to two hours after charging before checking voltage.
Running an onboard charger for a 12V trolling motor? The 12 Volt Trolling Motor Kit with On-Board Charging Connection Kit keeps wiring clean and charging simple.
Setup Tips Our Customers Wish They Knew
Wake the battery before your first trip
To save power during shipping and storage, the 24M100 has a sleep mode. If it reads 0 volts out of the box, it is asleep, not dead. Press and hold the TEST button for about 3 seconds until the three indicator lights turn on from bottom to top. To put it back to sleep for off-season storage, hold TEST for 3 seconds until the lights turn off from top to bottom. One reviewer lost a day of fishing before learning this, so make it part of your install checklist.
Read the built-in state-of-charge indicator
Once awake, a quick press of TEST shows the charge level: three lights means ready to use, two lights means you should charge soon, and one light means recharge immediately.
Secure it properly
The 24M100 is IP67 rated, which means it is dust-tight and protected against temporary immersion. Still mount it in a battery box or secured tray like any marine battery. The NOCO Group 24 Snap-Top Battery Box and NOCO Group 24 Battery Tray are sized for it.
Lean on Pro-Boost if you run it flat
If the battery is ever fully discharged, the onboard Pro-Boost jump-start system helps recover it so you are not stranded with a battery that refuses to take a charge.
24M100 vs. 31M100: Which Should You Choose?
Both are Pro-Guide 12V 100Ah LiFePO4 deep cycle batteries with the same performance. The difference is the case. Choose the 24M100 if your compartment, tray or battery box is sized for Group 24, or if you want to save space for a second battery or gear. Choose the 31M100 if you already have a Group 31 compartment. Before ordering, measure the height of your compartment and the clearance above the terminals: the 24M100 is 9.19 in tall.
Frequently Asked Questions
Is a Group 24 lithium battery the same size as a Group 24 AGM?
Yes. Group 24 is a case-size standard, so the 24M100 (10.25 x 6.83 x 9.19 in) fits Group 24 battery boxes and trays. Always confirm height and terminal clearance in your compartment.
How many amp-hours is a Group 24 lithium battery?
It varies by brand and model. The Pro-Guide 24M100 is 100Ah (1,280Wh), which is more usable capacity than most Group 24 AGM or lead-acid batteries offer.
Can I use a 12V 100Ah lithium battery for a trolling motor?
Yes. One 24M100 runs a 12V trolling motor for about 3 hours at a 30A draw. Wire two in series for 24V or three in series for 36V motors.
Can the 24M100 start my outboard engine?
No. The 24M100 is a deep cycle battery and is not designed for engine starting. Pair it with a dedicated starting or dual-purpose battery.
How long does a LiFePO4 deep cycle battery last?
The 24M100 is rated for more than 3,000 cycles at 100% depth of discharge and more than 6,000 cycles at 80%. For many anglers that is well over a decade of use, and it is backed by a 10-year warranty.
Do I need a special charger for a lithium marine battery?
Use a charger with a LiFePO4 profile and a 14.6V cut-off, and avoid automatic desulfation modes. A dedicated lithium charger is the simplest way to get it right.
Is the 24M100 waterproof?
It is IP67 rated: dust-tight and protected against temporary immersion in water. Mount it in a battery box or secured tray.
Upgrade to Group 24 Lithium Power
If your boat, kayak or RV has a Group 24 slot, the Pro-Guide 24M100 is the easiest way to get 100Ah of lithium power, cut roughly half the weight and stop replacing batteries every few seasons. It is built for anglers who need power that lasts from launch to weigh-in, and it is backed by a 10-year warranty and a team that will help you choose the right setup.
Not sure which battery or charger fits your rig? Call our team at 1-800-827-3232 or browse all deep cycle lithium batteries and lithium chargers.
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