If you fish all day or run electronics on the water, the MillerTech 12V 100Ah Sport Series ends the routine of nursing a dying battery. This maintenance-free LiFePO4 deep cycle battery delivers its full 100 amp hours of usable power and holds a steady voltage from the first cast to the last, so your trolling motor pulls the same at 4 p.m. as it did at sunrise. At about 26.55 lb, it weighs roughly half of a lead-acid Group 24, which both your back and your boat's performance will notice.

It is built for anglers and boaters first: 12V trolling motors, fish finders, livewells, and boating electronics. It also works well beyond the water, in RV house-power banks, solar energy storage, tiny homes, kayaks, and shop backup power. Built-in Bluetooth lets you check state of charge, voltage, and battery health from your phone, while a smart BMS with low-temperature charge protection guards the cells automatically.

Because it is a true deep cycle battery, it is made to be drained and recharged day after day, not to crank an engine. If you need engine starting plus house power, choose the MillerTech Dual Purpose model instead. For a straightforward, long-lasting upgrade from lead-acid or AGM, the Group 24 Sport Series is a proven, drop-in-friendly choice backed by a 10-year repair-or-replace warranty.

Why Upgrade to Lithium

Switching from a lead-acid or AGM battery to LiFePO4 changes how your day on the water actually feels. Here is what the upgrade gives you:

• Roughly half the weight. About 26.55 lb versus 50 to 65 lb for a typical lead-acid Group 24. Easier to carry, and less weight to push around the lake.
  
  
• Use the whole battery. Lithium safely delivers close to its full 100Ah. A lead-acid battery is usually limited to about half its rating before you risk damaging it, so a 100Ah lithium gives you far more real, usable power.
  
  
• No power fade. LiFePO4 holds a flat, steady voltage through the discharge, so your trolling motor keeps its speed late in the day instead of slowing down as the battery drops.
  
  
• Lasts far longer. Rated for 3,000+ charge cycles, compared with roughly 300 to 500 for many lead-acid batteries. Fewer replacements over the life of your boat.
  
  
• Maintenance-free. No watering, no acid checks, no cleaning corrosion off the posts. Charge it and go.
  
  
• Faster, simpler charging. Recharge in hours with a lithium charger, and no memory effect if you top it off partway.
  
  
• Peace of mind. A built-in BMS protects against over-charge, over-discharge, and short circuits, and a 10-year repair-or-replace warranty stands behind it.

Features & Benefits

• LiFePO4 chemistry. A safe, stable lithium chemistry that runs cooler and lasts longer than lead-acid. Benefit: dependable power with a long service life.
  
  
• Full 100Ah (1,280Wh) usable capacity. Delivers close to the full rating. Benefit: more real runtime for trolling and electronics from a single battery.
  
  
• Built-in Bluetooth monitoring. The MillerTech app shows state of charge, voltage, and health. Benefit: know exactly how much power you have left at a glance, no guessing.
  
  
• Smart BMS protection. Manages voltage, current, and temperature, with protection against over-charge, over-discharge, and short circuit. Benefit: the battery protects itself so you do not have to babysit it.
  
  
• Low-temperature charge protection. The BMS blocks charging in freezing conditions. Benefit: prevents cold-charging damage and extends battery life.
  
  
• Sealed IP65 marine case. A rugged, gasket-sealed case with a stainless steel breather vent mounted on top. Benefit: handles splashes, humidity, and vibration on the boat.
  
  
• Heavy-duty M8 stainless steel terminals. Solid stainless posts designed to resist heat build-up. Benefit: secure, low-resistance connections for high-draw trolling motors.
  
  
• 4S-4P expandability. Connect up to four in series and four in parallel. Benefit: scale up to 24V, 36V, or 48V systems, or add capacity for longer days.
  
  
• Maintenance-free design. No watering or acid service. Benefit: less upkeep and no corrosion to clean.
  
  
• 10-year repair-or-replace warranty. Long-term coverage with shipping paid both ways. Benefit: a low-risk, long-term investment.

Applications

The Group 24 Sport Series is designed for continuous 12V deep cycle loads. It suits:

• Bass boats, aluminum boats, and fishing kayaks
  
  
• 12V trolling motors (and 24V, 36V, or 48V systems when wired in series)
  
  
• Fish finders, flashers, sonar, and livewell pumps
  
  
• RV house-power banks and 12V accessories
  
  
• Solar energy storage and off-grid cabins
  
  
• Tiny homes and shop or garage backup power
  
  
• General 12V LiFePO4 replacement for lead-acid or AGM deep cycle batteries

It is not designed for engine starting. For cranking an outboard plus running house loads, choose the MillerTech Dual Purpose model.

Runtime & Compatibility

Estimating runtime is simple: divide the usable capacity (about 100Ah) by the amps your device pulls. The table below shows rough estimates from a full charge. Real-world runtime varies with your speed setting, temperature, wind, current, and battery age.

Because trolling motors draw far fewer amps at lower speeds, real fishing use, where you speed up and slow down, commonly stretches a single battery across a full day. Running at a steady high speed shortens it.

Compatibility at a glance:

• Fits a standard BCI Group 24 tray (10.23 x 6.61 x 8.35 inches).
• 12V systems, with series wiring for 24V, 36V, or 48V trolling motors and parallel wiring for more capacity (up to 4S-4P).
• Charging: use a lithium (LiFePO4) charger with a 14.6V profile. A standard lead-acid or AGM charger is not recommended because desulfation and equalization modes can apply voltages the battery is not built to accept.
• Alternator charging is supported when the alternator's maximum output does not exceed 14.6V. Verify your output before connecting.
• Solar and inverter systems: compatible with standard 12V LiFePO4 charge settings.
• Not for engine cranking. This is a deep cycle battery; use the Dual Purpose model for starting.

Recommended MillerTech chargers

• 12V 10A (1210C): most economical; full charge in about 10 to 12 hours. Good for overnight or lighter daily use.
• 12V 20A (1220C): nearly twice as fast at about 5 to 6 hours. A strong pick for shop, RV, and solar use.
• 12V 20A On-Board (1220M): permanently mounted and IP65 waterproof. Plug into shore power after each trip. The top pick for on-board marine setups.
• Multi-bank and Dark Speed on-the-run chargers: for boats with several batteries, charge a whole bank from one plug, or top off a 12V bank plus a 24V or 36V trolling bank while you run.

Specifications

FAQ