A charging system comprising a plurality of cascaded devices, wherein the plurality of cascaded devices comprises at least one first charging device and at least one second charging device ; 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. <EOS>