Lithium battery charging and discharging control method and battery management system

The invention relates to a lithium battery charging and discharging control method and a battery management system. The method comprises the following steps that battery information is collected and a current capacity retention ratio is calculated; the state of the lithium battery is judged according to the capacity retention ratio, and then corresponding control parameters are selected and include the charging cut-off voltage x1*Vmax and the discharging cut-off voltage y1*Vmin in the initial state and the charging cut-off voltage x2*Vmax and the discharging cut-off voltage y2*Vmin in the middle stage, and x11. When the battery is controlled to be charged and discharged, charging and discharging operation is executed according to the current control parameters; the charging and discharging depth is reduced and the battery is protected to the greatest extent under the condition that the battery state is the best, and the charging and discharging depth is increased along with circulation when t