Fast charging is now a core feature of high-quality power banks. PD (Power Delivery) and QC (Quick Charge) are the two most widely used fast charging protocols on the market. USB PD is universal. It works well with iPhones, Android phones, tablets and even small laptops. It supports bidirectional fast charging, meaning the power bank itself can be recharged quickly via PD adapters. QC is mainly designed for compatible Android devices and delivers fast speed with stable current. A multi-protocol power bank automatically identifies connected devices and adjusts voltage and current safely. It will not force high-speed charging for gadgets that do not support fast charge. When buying wholesale power banks for resale, multi-protocol models attract more buyers. Clear marking of supported protocols helps customers avoid slow charging troubles.