FIG. 1 is a front elevational view of an emergency power supply showing our new design; FIG. 2 is a rear elevational view thereof; FIG. 3 is a left side view thereof; FIG. 4 is a right side view thereof; FIG. 5 is a top plan view thereof; FIG. 6 is a bottom plan view thereof; FIG. 7 is a perspective view thereof; and, FIG. 8 is another perspective view thereof.