The ornamental design for a “power bank,” as shown and described.
FIG. 1 is a front, top and right side perspective view of a power bank showing my new design;
FIG. 2 is another perspective view of a power bank showing my new design;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a rear elevational view thereof;
FIG. 5 is a left side elevational view thereof;
FIG. 6 is a right side elevational view thereof;
FIG. 7 is a top plan view thereof; and,
FIG. 8 is a bottom plan view thereof.
The broken lines shown in the figures on the top and bottom surfaces of the power bank are used to illustrate stitching and are part of the claimed design.
The broken lines shown in the figures on the front surfaces represent portions of the article which form no part of the claimed design.