Portable Battery

1. Portable battery 1 . 1 is a perspective view of a portable battery showing the claimed design; 1 . 2 is a front view thereof; 1 . 3 is a back view thereof; 1 . 4 is a right view thereof; 1 . 5 is a left view thereof; 1 . 6 is a top view thereof; and 1 . 7 is a bottom view thereof. The dashed broken lines in the reproductions illustrate portions of the portable battery that form no part of the claimed design. The dot-dash broken lines in the reproductions define the boundary of the claimed design and form no part of the claimed design.