Li-polymer Battery 503759 1200mAh 3.7V with JST-PH2.0 connector - 26AWG cables 100mm with PCMLithium 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 1200mAh for a total of about 4.5 Wh.The batteries come pre-attached with a 2-pin JST-PH connector as shown and include the necessary protection circuitry. 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 to recharge them and at a rate of 600mA or less.Like most lipos, the batteries we sell do not have thermistors built in. This is why we suggest charging at 1/2C or even less - 500mA max in this case which is how much you can get from a USB port.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. Polarity matches all Adafruit LiPoly/LiIon chargers and boards, other brands may have reverse polarity and can destroy your battery. 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 Output: 3000mAh at 3.7V nominal Connector: 2-pin JST-PH Cable: length 100mm, AWG 26 Dimensions: 5x37x59mm