Portable supplementary battery

FIG. 1 is a perspective view of a portable supplementary battery showing our new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a left side view thereof where the right side view is a mirror image;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom plan view thereof;

FIG. 7 is a front view shown in a state of use where the portable supplementary battery is connected to a mobile phone shown in broken lines; and,

FIG. 8 is a front view shown in a state of use where the portable supplementary battery is connected to a mobile phone shown in broken lines.

The broken lines depict portions of the portable supplementary battery that form no part of the claimed design.