Portable Power Bank

FIG. 1 is a front perspective view of a portable power bank showing my new design; FIG. 2 is a rear perspective thereof; 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 in the Figures are for the purpose of illustrating portions of the portable power bank that form no part of the claimed design.