The Battery Charging Hub for Phantom 4 Quadcopter from DJI is designed for use with the Phantom 4 Intelligent Flight Battery. When used with the Phantom 4 Battery Charger (available separately), it can charge up to three batteries in series. The batteries will be charged in sequence according to their power levels, starting with the battery that has the most charge. Storage Mode allows the Charging Hub to maintain a 50% charge, ensuring the voltage stays above the minimum safest level.