These are very slim, extremely light weight batteries based on Lithium Ion chemistry. Each cell outputs a nominal 3.7V at 850mAh! 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 LiPo 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. https://elecena.pl/product/7537794/lithium-ion-battery-850mah 2017-01-13 https://elecena.pl/product/7537794/lithium-ion-battery-850mah 2017-11-24 https://elecena.pl/product/7537794/lithium-ion-battery-850mah 2017-11-28 https://elecena.pl/product/7537794/lithium-ion-battery-850mah 2018-05-05 https://elecena.pl/product/7537794/lithium-ion-battery-850mah 2018-11-21 https://elecena.pl/product/7537794/lithium-ion-battery-850mah 2018-11-27 https://elecena.pl/product/7537794/lithium-ion-battery-850mah 2022-02-21 https://elecena.pl/product/7537794/lithium-ion-battery-850mah 2025-03-24 https://elecena.pl/product/7537794/lithium-ion-battery-850mah 2025-04-12 https://elecena.pl/product/7537794/lithium-ion-battery-850mah 2025-06-04 https://elecena.pl/product/7537794/lithium-ion-battery-850mah 2025-06-07