12V 40AH Sport Series Lithium Battery w/ Bluetooth (1240-BT)

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!

Recommended Charger. (See 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.

Capacity – 40Ah

This battery has a storage capacity of 40 amp-hours (Ah). That means it can deliver steady power for larger accessories and longer run-times than smaller capacity batteries.

Voltage – 12.8V

The battery operates at a nominal voltage of 12.8 volts. This allows it to directly replace traditional 12V lead-acid batteries while providing more stable and consistent output.

Weight – 14 lbs

This battery weighs 14 pounds. It is significantly lighter than a comparable lead-acid battery, making installation and transport easier.

Size – 7.6” × 5.2” × 7.25”

The battery measures 7.6 inches by 5.2 inches by 7.25 inches. Its compact footprint allows it to fit into many standard battery compartments without modification.

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.

Max Charge Voltage – 14.6V

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

Peak Discharge – 120A (3 Seconds)

The battery can deliver up to 120 amps for short bursts lasting up to 3 seconds. This allows it to handle high-demand startup loads such as motors or heavy electronics.

Cut-Off Voltage – 10V

The battery has a low-voltage cut-off at 10 volts. This protects the cells from over-discharge and helps preserve long-term performance.

Max Charge / Discharge Current – 40A

The battery supports up to 40 amps of continuous charge and discharge current. This defines the safe operating range for sustained power draw and charging input.

Operating Temperature – -4°F to 140°F

The battery is designed to operate in temperatures ranging from -4°F to 140°F. This wide temperature tolerance makes it suitable for 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, helping protect the cells from damage.

Cell Type – Prismatic

This battery is constructed using prismatic lithium cells. Prismatic cells allow for higher capacity in a compact footprint and efficient internal packaging.

Terminals
Built with heavy-duty M8 stainless steel terminals and a robust 4S-4P configuration for powerful performance without excessive heat.

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

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!

Be sure to download the product manual for more details.

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 40Ah 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