12V 135AH Heated Starting Battery w/ BT

The Millertech 12V 135AH HEATED Dual Purpose Starting Battery

Dual Purpose Batteries LiFeP04 are quickly becoming a popular item that many enthusiasts demand. Our team of Engineers and Technicians are a very aggressive group and were not willing to take a backseat on this trend. This battery has enough cranking amps to start even the largest engines in the industry, plus they have enough reserve capacity to power multiple power hungry graphs for 8 plus hours. These Dual Purpose models will change the way anglers think about there power needs forever.

Heated:

This Heated battery delivers reliable cold-weather performance with built-in smart heating technology. When connected to a charger and the internal temperature drops to 32°F, the heater automatically activates, raising the temperature to 34°F before resuming charging. This ensures dependable starts and steady power in frigid conditions.

Recommended Charger
(see chart and info under the recommended charger tab)

The Sport Series Marine Batteries

The Sport Series Marine batteries are all sealed with a thick rubber gasket along the lid connection point. This means they are Marine approved IP65 rated. A completely sealed battery case will cause condensation, so we build them with a marine grade Stainless Steel breather vent. Our vent sits on the top of the case unlike some others where the vent sits down inside catching rain and dirt.

Custom molded, heavy duty, re-closable battery case. This means if you ever have an issue with your battery no matter is it in year 5 or year 15 we will always have easy access to repair any defective parts. This custom case also has convenient hold down strap grooves molded into the side corners helping to keep your straps seated securely in place.

Weight – 33lbs

The battery weighs 33 pounds. It is significantly lighter than a comparable lead-acid starting battery, reducing overall vehicle or equipment weight.

Size – 13” × 6.75” × 9”

BCI Group Size 31

(This is a standardized battery case size defined by the Battery Council International (BCI). It tells you the battery’s physical dimensions and terminal layout. The battery measures 13 inches by 6.75 inches by 9 inches. Its Group Size 31 dimensions allow it to fit standard battery trays designed for that footprint. Need a tray? Purchase them here.

Terminals
Built with heavy-duty M8 bolts/washers in 18-8 stainless steel. If multiple lugs are used, the washers may be removed, or longer bolts may be required to fully seat the bolt into the copper pillar.

Battery Management System (BMS)

The battery includes an integrated Battery Management System (BMS). The BMS protects against over-charging, over-discharging, excessive current, and unsafe temperatures to extend battery life.

Efficiency – 98%

The battery operates at 98% energy efficiency. This means nearly all stored energy is usable, resulting in longer run-times and faster charging.

Memory Effect

This battery has no memory effect. You can charge it at any state of charge without reducing overall capacity over time.

Built-In Bluetooth
Equipped with Bluetooth technology. The battery connects to an app that allows you to conveniently monitor multiple batteries at once—no more checking multiple apps. You can download the app here

Max Charge Voltage – 14.6V

The maximum charging voltage for this battery is 14.6 volts. Charging within this range ensures a full charge while protecting internal cells.

Max Charge / Discharge Current

The battery supports up to 135 amps of continuous charge and discharge current. This defines the safe operating range for sustained high-power loads and charging input.

Peak Discharge – 300A

The battery can deliver up to 300 amps for short bursts (up to 5 sec.). This allows it to support engine starting or sudden high-load demands.

Cut-Off Voltage – 10V

The battery has a built-in low-voltage 10V cut-off. This prevents over-discharge and protects the cells from damage to extend service life.

Operating Temperature:

The battery is designed to operate in temperatures ranging from 0°F to 130°F. This wide range allows reliable use in both cold and hot environments.

Low-Temperature Charging Protection 

The battery includes built-in low-temperature charging protection. This prevents charging in freezing conditions to protect the cells. Charging Temp. Range: 25°F-131°F

Cell Type – Prismatic

This battery is constructed using prismatic lithium cells. Prismatic cells allow higher capacity.

Robust Design for Longer Life
Robust yet lightweight, Millertech Sport Series Lithium Batteries can last up to 10X longer than AGM or lead-acid batteries. Never be stranded with a dead battery again!

Simple 10 Year Warranty
From the date of your battery purchase through year number 10 of ownership, your battery is covered. If it stops working during this time, we will repair or replace it with a battery of equal or greater value for FREE!

THE MILLERTECH® SPORT SERIES LITHIUM BATTERY
10 YEAR GUARANTEED WARRANTY IS SIMPLE!

TERMS:

From the date of your battery purchase through year number 10 of ownership, your battery is covered. If it stops working during this time, we will repair or replace it with a battery of equal or greater value for FREE!

SHIPPING:

We cover all shipping costs associated with shuttling your battery back and forth for repair or replacement. It is our warranty; it is our cost; not yours.

EXCLUSIONS:

There are NONE! You trusted Millertech®, and if it’s within the warranty period your Millertech® battery is completely covered for everything!

PROOF OF PURCHASE:

You don’t need one. If it’s Millertech®, it’s covered!

FOR WARRANTY SERVICE CALL: 855-MAX-LITH

EMAIL:  warranty@millertechenergy.com

Recommended Chargers

The Millertech 12V 135Ah Dual Purpose Heated lithium battery is engineered for a max charge voltage of 14.4V charging profile.

1) 12V 10A Charger (1210C)

What it is: A small 110V AC plug-in lithium charger that outputs 14.6V at 10A (2-stage).  Typical speed (100Ah battery): roughly 10–12 hours from low to full (real-world varies). Why choose it:

• Most Economical option

• Good if you charge overnight or you don’t drain the battery hard each day

• Handy when charging off a solar + inverter type setup (smaller AC charger). 

2) 12V 20A Charger (1220C)

What it is: A small 110V AC plug-in lithium charger that outputs 14.6V at 20A (2-stage; automatic fuse).  Typical speed (100Ah battery): roughly 5-6 hours 

Why choose it:

• You want the same simle plug-in AC charger, but almost twice as fast

• A better option for those who use the battery hard and want same-day recharge

3) 12V 20A On-Board Charger (1220M)

What it is: The 1220M is a single-bank, permanently mounted lithium charger designed mainly for boats and other setups where the charger stays installed on the equipment. It runs on 110 V AC input and outputs about 14.5 V at 20 amps, with a charging profile designed specifically for LiFePO₄ batteries. It also has an IP65 waterproof rating, making it suitable for wet or marine environments

.  Typical speed (100Ah battery): roughly 5-6 hours 

Why choose it:

• Permanent Installation:

  • Ideal for bass boats, trolling motor batteries, or electronics batteries

  • Just plug in shore power and it charges automatically.

• Waterproof/Marine Durability:

  The IP65 waterproof rating means it can handle splashes, humidity, and vibration typical in boats.

4) 12V-24V Dark Speed “On The Run” Dual Marine Charger

A dual-output marine charger that can charge a 12V bank and a 24V bank (listed outputs: 14.5V 15A and 28.8V 15A) and is IP65. It’s designed around the idea of charging “on the run,” using your system while operating, with logic to protect/priority-manage the starting battery.

Why choose it:

• You run a 12V + 24V system (great in Marine Setups: starting/house + 24V Trolling)

• You want charging while you are out (less dependence on shore power or generator)

• You want ‘smart’ behavior (prioritize starting battery, protections, BMS wake-up)

5) 12V-36V Dark Speed “On The Run” Dual Marine Charger

Same concept as #3 above, but for 12V + 36V (outputs: 14.5V 15A and 42.6V 15A) and is IP65.

Why choose it:

• You run a 36V system 36V Trolling motor lithium bank plus a 12V battery system

• You want “all-day” convenience of topping up while operating, and the built-in protections/priority behavior

6) Millertech 12V 15A 2-Bank Battery Charger (Model# 1215-2)

The Millertech 12V 15A 2-Bank Battery Charger (Model 1215-2) is an onboard lithium charger designed to charge two separate 12-volt batteries at the same time from one unit. It’s commonly used in marine setups where a boat has multiple batteries—such as a starting battery and an electronics battery. The charger is part of Millertech’s multi-bank lineup and is typically used when you want to charge multiple batteries overnight with a single plug-in connection.

This charger has two independent charging banks, each delivering about 15 amps, so each battery receives the proper charge without affecting the other. Because the banks are isolated, the charger automatically manages each battery individually to maintain proper charging and battery health.

Permanent Marine Installation. This is an onboard charger, meaning it is mounted permanently in the boat. After a day on the water you simply plug the boat into shore power and it charges everything automatically.

7) Millertech 12V 15A 3-Bank Battery Charger (Model# 1215-3)

Same concept as #6 above, but allows 3 batteries instead of 2, to be charged at once.

8) Millertech 12V, 16V, 24V, 3-Bank Battery Charger (Model#121624-3)

Same concept as #6 and #7 above, but allows 3 batteries – a  12v, 16v and 24v to be charged at once.

This charger has three independent charging banks, allowing you to charge multiple batteries simultaneously without needing separate chargers. Each bank can be configured for different battery voltages:

• 12V battery bank – commonly used for electronics or starting batteries

• 16V battery bank – often used for high-performance marine electronics systems

• 24V battery bank – commonly used for trolling motor batteries

Because each bank is isolated, the charger can deliver the correct charging profile to each battery independently, which helps maintain battery health and efficiency.

9) Millertech 12V, 16V 36V, 3-Bank Battery Charger (Model#121636-3)

Same concept as #6 and #7 above, but allows 3 batteries – a  12v, 16v and 36v to be charged at once.