Polymer Lithium Ion Battery - 40mAh

This is an extremely tiny and light weight battery based on the new Polymer Lithium Ion chemistry. This is the highest energy density currently in production. Each cells outputs a nominal 3.7V at 40mAh. This may sound like not so much power, but the cell is really tiny… like, about half an inch square!

Comes terminated with a standard 2-pin JST-PH connector - 2mm spacing between pins. These batteries require special charging. Do not attempt to charge these with anything but a specialized Lithium Polymer charger. Battery includes built-in protection against over voltage, over current, and minimum voltage. Please use caution when using this battery in wearable projects. When using conductive thread, a short in the thread can create sparks and heat. We recommend using coin cell batteries for beginners.

Note: This battery is not available to ship to Alaska or Hawaii, or through any express services (2-day, overnight), or internationally. This is temporary! Check out our blog post for more information. Additionally orders may take longer to process and therefore do not qualify for same-day shipping. Sorry for any inconvenience this may cause!

Note: This item is non-returnable. If this item arrives damaged or is not functioning properly, please do not hesitate to contact us to see if further actions may be taken.

  • Rated Capacity: 40mAh
  • Nominal Voltage 3.70V

Polymer Lithium Ion Battery - 40mAh Product Help and Resources

LilyPad Basics: Powering Your Project

September 24, 2018

Learn the options for powering your LilyPad projects, LiPo battery safety and care, and how to calculate and consider power constraints on your projects.

Adjustable LiPo Charger Hookup Guide

September 28, 2017

The SparkFun Adjustable LiPo Charger is a single-cell lithium polymer (LiPo) and lithium ion battery charger. Because it’s adjustable, this charger will be able to safely charge all of our singe-cell batteries.

Battery Technologies

February 6, 2013

The basics behind the batteries used in portable electronic devices: LiPo, NiMH, coin cells, and alkaline.

Core Skill: Electrical Prototyping

If it requires power, you need to know how much, what all the pins do, and how to hook it up. You may need to reference datasheets, schematics, and know the ins and outs of electronics.

2 Electrical Prototyping

Skill Level: Rookie - You may be required to know a bit more about the component, such as orientation, or how to hook it up, in addition to power requirements. You will need to understand polarized components.
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Customer Comments

  • What chip is on here that’s doing overcharge protection(?) It’s not shown in the data sheet (or I missed it). If that’s the case, can’t we simply charge these by using current limiting with a simple resistor?

  • I make my own design with the LTC4081 from Linear or the STNS01 from ST.

  • How can you charge one of these little 40mah lipos?

  • I guess there is a mistake in the Datasheet. The black wire is written as + and the red wire is written as -.

  • What can we use to charge these? I don’t see any charger boards in your catalog that do anything under 100mA…

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