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.

Battery includes built-in protection against over voltage, over current, and minimum voltage.
Note: These batteries require special charging so please do not attempt to charge these with anything but a specialized Lithium Polymer charger. Please use caution when using this battery in wearable projects. When using conductive thread, a short in the thread can create sparks and heat.