A charging system (100, 200) comprising a plurality of cascaded devices, wherein the plurality of cascaded devices comprises at least one first charging device (10a, 231) and at least one second charging device (10c, 234); wherein each of the at least one first charging device comprises: a housing; at least one first accommodation portion disposed at the housing and used for mounting a first energy storage device, wherein the first charging device is configured for charging the first energy storage device mounted to a first accommodation portion of the at least one first accommodation portion; and a second connecting port for connecting one of the at least one second charging device or another first charging device; wherein each of the at least one second charging device comprises: a housing; at least one second accommodation portion disposed at the housing and used for mounting a second energy storage device, wherein the second charging device is configured for charging the second energy storage device mounted to a second accommodation portion of the at least one second accommodation portion; and a first connecting port for connecting one of the at least one first charging device or another second charging device; characterized in that the first accommodation portion and the second accommodation portion have different shapes or dimensions; and the first connecting port and the second connecting port are used for inputting a current or outputting a current, and the first connecting port and the second connecting port are configured for being used interchangeably. a housing; at least one first accommodation portion disposed at the housing and used for mounting a first energy storage device, wherein the first charging device is configured for charging the first energy storage device mounted to a first accommodation portion of the at least one first accommodation portion; and a second connecting port for connecting one of the at least one second charging device or another first charging device; wherein each of the at least one second charging device comprises: a housing; at least one second accommodation portion disposed at the housing and used for mounting a second energy storage device, wherein the second charging device is configured for charging the second energy storage device mounted to a second accommodation portion of the at least one second accommodation portion; and a first connecting port for connecting one of the at least one first charging device or another second charging device; characterized in that the first accommodation portion and the second accommodation portion have different shapes or dimensions; and the first connecting port and the second connecting port are used for inputting a current or outputting a current, and the first connecting port and the second connecting port are configured for being used interchangeably. a housing; at least one second accommodation portion disposed at the housing and used for mounting a second energy storage device, wherein the second charging device is configured for charging the second energy storage device mounted to a second accommodation portion of the at least one second accommodation portion; and a first connecting port for connecting one of the at least one first charging device or another second charging device; characterized in that the first accommodation portion and the second accommodation portion have different shapes or dimensions; and the first connecting port and the second connecting port are used for inputting a current or outputting a current, and the first connecting port and the second connecting port are configured for being used interchangeably.