Lithium ion polymer (also known as 'lipo' or 'lipoly') batteries are thin, light and powerful. The output ranges from 4.2V when completely charged to 3.7V. This battery has a capacity of 500mAh for a total of about 1.9 Wh.
The batteries come pre-attached with a genuine 2-pin JST-PH connector as shown and include the necessary protection circuitry. So you can plug it right into your Feather, using the little port on the side. It will only plug in one way.
If the battery is plugged into the Feather and the USB cable is connected to a computer or power supply it will automatically recharge the battery. The yellow LED will light up to let you know. When the yellow light turns off, the battery is done charging
The battery will run most projects for 5-10 hours (depending on what is attached) and recharges in about 5 hours.
The included protection circuitry keeps the battery voltage from going too high (over-charging) or low (over-use) which means that the battery will cut-out when completely dead at 3.0V. It will also protect against output shorts. However, even with this protection it is very important that you only use a LiIon/LiPoly constant-voltage/constant-current charger (like the one built into the Feather) to recharge it!
Additional safety notes: Do not use a NiMH/NiCad/lead-acid charger! Also, do not abuse these batteries, do not short, bend, crush or puncture. Never charge or use unattended. Always inspect batteries and surrounding circuitry constantly for any damage, loose wiring, or possibility of short circuits. As with all Lithium ion polymer batteries and with any power source - they should be used by experts who are comfortable working with power supplies.
The Li Poly battery is not required for any projects - if you prefer not to use the battery simply dispose it at your local battery recycling/disposal center.