This is a very small, extremely lightweight battery based on Lithium Ion chemistry, with the highest energy density currently in production. Each cell outputs a nominal 3.7V at 400mAh! Comes terminated with a standard 2-pin JST-PH connector with 2mm spacing between pins. These batteries require special charging; do not attempt to charge these with anything but a specialized Lithium Polymer charger. The 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](https://www.sparkfun.com/search/results?term=coin+cell+battery). **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](https://www.sparkfun.com/news/2248) for more information. Additionally orders may take longer to process and therefore do not qualify for [same-day shipping](https://www.sparkfun.com/support#Same-DayShipping). 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. **Weight:** 9g **Features:** * Rated Capacity: 400mAh * Nominal Voltage 3.70V * Max Charge Current: 1C (400mA) * Normal Charge Current: 0.2C (80mA) * 1.06\" x 1.48\" x 0.2\" (26.5mm x 36.9mm x 5mm) **Documents:** * [MSDS](https://cdn.sparkfun.com/datasheets/Prototyping/MSDS%20603450.pdf) * [Datasheet](https://cdn.sparkfun.com/datasheets/Prototyping/spe-00-502535-400mah-en-1.0ver.pdf)