I claim the ornamental design for a battery case, as shown and described.
FIG. 1 is a front perspective view of a battery case 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;
FIG. 7 is a bottom plan view thereof;
FIG. 8 is a rear perspective view thereof; and,
FIG. 9 is a rear, right side perspective view showing the battery case in a state of use, with the two supports in an extended position.
The broken lines in the drawings are for the purpose of illustrating environmental subject matter and portions of the battery case that form no part of the claimed design.