An adapter (100; 200; 300), comprising: an input port (20; 80) coupleable to a single-voltage output interface of a single-voltage battery pack or to a multi-voltage output interface (10") of a multi-voltage battery pack; an output port electrically connected to the input port (20; 80) and coupleable to a single-voltage input interface of a first power tool or to a multi-voltage input interface (20"; 30") of a second power tool, wherein the single-voltage output interface of the single-voltage battery pack is coupleable to the single-voltage input interface of the first power tool, but not coupleable to the multi-voltage input interface (20"; 30") of the second power tool, and the multi-voltage output interface (10") of the multi-voltage battery pack is coupleable to the multi-voltage input interface (20"; 30") of the second power tool, but not coupleable to the single-voltage input interface of the first power tool; a switching mechanism (40; 60, 70; 90) switchable between a first state and a second state; and a housing for accommodating the input port (20; 80), the output port and the switching mechanism (40; 60, 70; 90); characterized in that the adapter is configured such that when the input port (20; 80) is coupled to the single-voltage output interface of the single-voltage battery pack and the switching mechanism (40; 60, 70; 90) is in the first state, the second power tool is coupleable to the output port and powerable by the single-voltage battery pack, and when the input port (20; 80) is coupled to the multi-voltage output interface (10") of the multi-voltage battery pack and the switching mechanism (40; 60, 70; 90) is in the second state, the first power tool is coupleable to the output port and powerable by the multi-voltage battery pack. an input port (20; 80) coupleable to a single-voltage output interface of a single-voltage battery pack or to a multi-voltage output interface (10") of a multi-voltage battery pack; an output port electrically connected to the input port (20; 80) and coupleable to a single-voltage input interface of a first power tool or to a multi-voltage input interface (20"; 30") of a second power tool, wherein the single-voltage output interface of the single-voltage battery pack is coupleable to the single-voltage input interface of the first power tool, but not coupleable to the multi-voltage input interface (20"; 30") of the second power tool, and the multi-voltage output interface (10") of the multi-voltage battery pack is coupleable to the multi-voltage input interface (20"; 30") of the second power tool, but not coupleable to the single-voltage input interface of the first power tool; a switching mechanism (40; 60, 70; 90) switchable between a first state and a second state; and a housing for accommodating the input port (20; 80), the output port and the switching mechanism (40; 60, 70; 90); characterized in that the adapter is configured such that when the input port (20; 80) is coupled to the single-voltage output interface of the single-voltage battery pack and the switching mechanism (40; 60, 70; 90) is in the first state, the second power tool is coupleable to the output port and powerable by the single-voltage battery pack, and when the input port (20; 80) is coupled to the multi-voltage output interface (10") of the multi-voltage battery pack and the switching mechanism (40; 60, 70; 90) is in the second state, the first power tool is coupleable to the output port and powerable by the multi-voltage battery pack.