Spend more of your day fishing and less of it worrying about power. The Millertech 36V 60Ah Marine Trolling Battery lets you replace three heavy lead-acid batteries with one lightweight lithium battery that keeps your 36-volt trolling motor running at steady speed from your first cast to your last.

This single Group 31 lithium battery takes the place of three 12V Group 27 lead-acid or AGM batteries, cutting more than 50% of the weight and clearing space in your battery compartment. Because it uses a flat lithium (LiFePO4) voltage curve, it holds strong power deep into the day instead of fading like lead-acid, so your Minn Kota, Motorguide, or Lowrance motor does not slow down as the charge drops. Anglers run it on bass boats, walleye and multi-species rigs, bay boats, and pontoons with 36-volt trolling motors up to 112 pounds of thrust.

Check your power level from your phone at any time. Built-in Bluetooth links to the MillerTech App and shows how much charge is left, how much power the motor is pulling, and how long charging will take, so there is no guessing about whether you can make one more pass. A sealed marine case handles salt, spray, and vibration, and a 10-year full repair or replace warranty backs it for the long haul.

Choose the variant that fits how you charge:

• Standard (3660-BT): The right choice for most anglers. It runs in cold weather and includes low-temperature charging protection. Best when you charge in above-freezing conditions or store your boat indoors.
• Heated (3660-BTH): Adds a built-in heater that turns on at 32°F so you can safely charge in below-freezing weather. Best for ice-out openers, cold-front tournaments, and boats stored unheated.

Both variants share the same 60Ah capacity, motor compatibility, chargers, app, case, and 10-year warranty. The only difference is the heated variant's ability to charge below freezing.

Key Features

• All-day steady speed: The flat lithium voltage curve keeps power consistent as the battery drains, so your trolling motor holds the same speed late in the day instead of slowing down like it does on lead-acid.
  
  
• One light battery instead of three heavy ones: A single Group 31 lithium battery replaces three 12V lead-acid batteries, removing more than 50% of the weight and cleaning up your wiring so there is less to install and maintain.
  
  
• Know exactly how much power is left: Bluetooth and the MillerTech App show charge level, live power draw, remaining capacity, and time-to-full, so you can plan your day and stop guessing about when to head in.
  
  
• Protection built in: The smart battery management system automatically guards against overcharge, over-discharge, over-current, short circuit, and overheating, and balances the cells so the battery lasts longer with no effort from you.
  
  
• Charge in freezing weather (Heated variant): The heater turns on at 32°F and warms the cells so you can charge below freezing, which a standard lithium battery cannot do. Ideal for cold-season and early-spring fishing.
  
  
• Built for the water: A gasket-sealed, IP65-rated case with a top-mounted stainless steel breather vent stands up to spray, vibration, and condensation in freshwater and saltwater.
  
  
• Serviceable and warrantied for 10 years: The reclosable case allows repair access years down the road, and the 10-year full repair or replace warranty means the company stands behind it.
  
  
• Independently tested and certified: UL Certified to ANSI/CAN/UL 1973:2022 Ed.3 and ETL Listed (Intertek), so you can trust the safety of what you are installing on your boat.

Boat & Motor Compatibility

The 36V 60Ah is built for 36-volt trolling motors up to 112 pounds of thrust. Most anglers run a single battery; many add a second in parallel for longer days and a backup on the water. This applies to both the Standard and Heated variants.

Works with 36V trolling motors including:

• Minn Kota Ultrex, Ultrex Quest, Terrova, Riptide Terrova, Fortrex, Ulterra, and Ulterra Quest (36V)
• Motorguide Xi5, Xi3, Tour, and Tour Pro (36V)
• Lowrance Ghost and Lowrance Recon (36V)
• Newport and other 36V bow-mount and kayak trolling motors

Commonly used on boats such as:

• Bass boats Ranger, Skeeter, Nitro, Bass Cat, Stratos, Phoenix, Triton, Blazer
  
  
• Walleye and multi-species boats Crestliner, Lund, Alumacraft, and similar aluminum deep-V rigs
  
  
• Bay boats, center consoles, Carolina skiffs, and pontoons running a 36V bow-mount motor
  
  
• Guide boats and fishing kayaks powered by a 36V trolling motor, including cold-weather and early-season fisheries

Note: This is a 36-volt battery for your trolling motor. Your 12V electronics, such as fish finders and live sonar, should be powered by a separate 12V battery, not directly from this 36V battery.

Charging & Compatible Chargers

Use a 36V lithium (LiFePO4) charger only. Do not use a lead-acid or AGM charger, which will not fully charge the battery and can shorten its life. Both variants accept up to 60A of charge current, and MillerTech lists a recommended charge current of 15A. The 36V 15A on-board charger matches that recommendation, while the 25A option charges faster to get you back on the water sooner, both charge safely. On the Heated variant, the heater turns on at 32°F and runs on charger power, so in cold weather keep the charger connected to warm the cells before charging begins.

The MillerTech App shows time-to-full when a charger is connected. You can combine chargers, recharge on the water during the day with the on-the-run charger, then top off at the dock overnight.

Specifications

Specifications apply to both the Standard (3660-BT) and Heated (3660-BTH) variants. The Heated variant adds the built-in low-temperature heating noted below.

Note on charge temperature: The Standard variant (3660-BT) charges from 32°F to 125°F; its BMS low-temperature charging protection pauses charging below freezing to prevent cold-charge damage. The Heated variant (3660-BTH) charges from 25°F to 131°F, using its built-in heater to warm the cells to a safe charging temperature in the cold. Both variants discharge and run down to -4°F.

FAQ