TiLECC TC8516Mini 4-wire 20000 MAh Digital Display LED Light Compact Portable Power Supply

The rated total capacity of the internal battery cells in a power bank (e.g., 20000mAh) is measured at 3.7V. ● Standard charging voltage for devices like smartphones is 5V. Voltage conversion and boosting occur during discharge, inevitably causing energy loss. ● Therefore, the actual effective output capacity of a power bank is approximately 60%-70% of its nominal total capacity. ● Example: A power bank with a nominal capacity of 20000mAh will provide approximately 12000-14000mAh of usable charging capacity for devices (actual values vary depending on the device and usage conditions).