Electricity-supplementing and sorting method and device for reducing dynamic voltage difference among multiple strings of parallel battery packs

The invention discloses an electricity-supplementing and sorting method and device for reducing a dynamic voltage difference among multiple strings of parallel battery packs. According to the technical scheme, multiple single batteries are charged by using constant power P within specific time t1 separately, and then the batteries are ganged according to a capacity difference, an internal resistance difference, a voltage difference and a self-discharge difference among the single batteries. By adopting a constant-power electricity supplementing method, energy states of the single batteries are kept consistent after electricity supplementing is completed, the technical problem that the dynamic voltage difference is large after the batteries are ganged due to the fact that inconsistent charged states or energetic states of the single batteries are easily caused by a constant-current and constant-voltage charging or constant-current charging mode in the prior art is solved, the dynamic voltage difference among t