This is a 2S 7.4V Lithium Battery Pack built using 1800mAh 18650 cells. All the cells are connected in series and thus provide a nominal output voltage of 7.4volts. The battery pack consists of an in-built BMS which ensures safe operation of the cells during charging and discharging.  Specification Charging Voltage- 8.4V Charging Current- 900mA Nominal Pack Voltage- 7.4V Discharge Current- Tested for 500mA, 1A.1.5A Max. Discharge Current – 1.8A Protection (Included BMS) Short Circuit Protection Upper charge cut-off threshold : 8.4V Lower cutoff threshold : 5.5V Applications: Small scale UPS Battery Battery for GPS Tracking – Vehicle Tracking – Asset Tracking Wifi Modem or Router Battery for backup PSP Industrial Machines Emergency Lights Robotics and RC cars Music Players and Audio Systems How to charge this 7.4V lithium battery pack? The battery pack can be charged and discharged using the same DC Jack connector. To charge the battery just connect it to a female DC barrel connector and provide 8.4V (4.2V per cell) to the positive pin and ground to the negative pin. Monitor the increase in the voltage with time and stop charging after the pack has reached more than 8.2V. Using RPS to charge the cell will provide better control and understanding.  When to charge the battery pack? Disconnect the cells from the load when the voltage has dropped to 6V (3V per cell) or below and charge them before you can use them again. Over discharging the cells might damage them permanently. Note: Lithium batteries can become unstable, if not handled properly, resulting in heat or fire. Safety precautions and prior knowledge is advised.  Warranty Terms: This battery pack comes with 1 year warranty from the date of purchase. Warranty is void if the pack/connector is physically damaged.