A power adapter, an electronic equipment, a battery charging system and a battery charging method are provided. The power adapter include a communication interface and charges via the communication interface a battery of the electronic equipment; during charging a battery, the power adapter is configured to: first charge the battery in a regular charging mode; when an output current value of the power adapter falls within a regular current range for a predefined time period, send a quick charge inquiry instruction to the electronic equipment; after receiving a quick charge command sent by the electronic equipment, adjust an output voltage according to battery voltage information fed back by the electronic equipment; and if the output voltage meets a quick charge voltage requirement predefined, adjust an output current and the output voltage according to a quick charge mode so as to charge the battery.