Built-in rechargeable 6000mAh Lithium Polymer battery uses more energy (15W to 20W rather than modem phone's 10W) to charge the phone. in order to optimize power transfer in the early stages of charging. QC 3.0 is newest technology standard for quick charging that uses an intelligent system of negotiation between the phone and the charger, where the phone finds the most efficient charge point and pulls only as many volts and amps that are needed.