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

(6 Reviews)
$299.00

Free shipping

Applications For This Battery

12V40AH Sport Series Lithium Battery with Bluetooth and Built in low-temp charging protection! (1240-BT).

Download ManualDownload Sports Series WarrantyApple StoreGoogle Playstore

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Capacity
40AH
Voltage
12.8V
Weight
14 lbs
Size
7.6” x 5.2” x 7.25”
Warranty
10 years

BMS: Yes
Chemistry: LFP
Efficiency: 98%
Memory: None
Max Charge/Voltage: 14.6V
Peak Discharge: 120A – 3sec
Cut-off Voltage: 10V
Max Charge/Discharge Current: 40A
Operating Temp: 32°F – 130°F
Low Temp Charging Protection: Yes
Cell Type: Prismatic
Bluetooth: Yes

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

The Millertech 12V 40Ah lithium battery is engineered for a precise 14.6V charging profile.  For maximum performance, battery health, and a true 100% charge, the Millertech 12V 10A Lithium Battery Charger (1210C) is strongly recommended.

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

Customer Reviews

Ron gray
Rating: 5/5
Service oriented company beyond compare.
Bought 2 100 amp for bow Minn Kota, one 100 amp for 115 hp Mercury one year ago. Did a lot of research with different lithium battery manufactures and none of them compared to Miller Techs knowledge, expertise and willingness to assist me. Wonderful product and getting ready to order a 40 amp for my forwarding face sonar with their battery charger.
Sat Jan 24 2026 19:02:17 GMT+0000 (Coordinated Universal Time)
Joe Becker
Rating: 5/5
Quality product!
12V 40AH Sport Series Lithium Battery w/ Bluetooth (1240-BT)
Wed Nov 05 2025 13:33:26 GMT+0000 (Coordinated Universal Time)
Christopher Sanno
Rating: 5/5
Great Product
The 40 Amp Hour is Perfect for my Garman 106SV with Live scope bundle. I’m able to fish 14 hours a day without worries.
Tue Aug 19 2025 23:21:40 GMT+0000 (Coordinated Universal Time)
Cheryl Bevan
Rating: 5/5
12V 40AH Sport Series Lithium Battery w/ Bluetooth (1240-BT)
Wed Jun 18 2025 00:31:32 GMT+0000 (Coordinated Universal Time)
Tripp Poplin
Rating: 5/5
Best batteries available
Tue Apr 01 2025 14:47:46 GMT+0000 (Coordinated Universal Time)
Larry Treece
Rating: 5/5
Battery
Shipping was fast. Haven’t hooked up the battery yet but I’m sure it will work fine.
Thu Dec 05 2024 15:10:00 GMT+0000 (Coordinated Universal Time)

What the pros are saying about Millertech batteries