I claim the ornamental design for a storage battery, as shown and described.
FIG. 1 is a perspective view of a storage battery, showing my new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a left side elevational view thereof;
FIG. 5 is a right side elevational view thereof;
FIG. 6 is a top plan view thereof; and
FIG. 7 is a bottom plan view thereof; and,
FIG. 8 is a perspective view showing the claimed design with the handle in an open position. The broken line showing of the music player and the connector is included for the purpose of illustrating environment and forms no part of the claimed design.