The ornamental design for a badmintonnetbase, as shown and described.
FIG. 1 is a perspective view of a badminton net base showing our new design together with environmental elements;
FIG. 2 is a top perspective view showing the design in a closed state, and without the environmental elements;
FIG. 3 is a top perspective view showing the design in an open state, and without the environmental elements;
FIG. 4 is a top plan view of FIG. 3;
FIG. 5 is front view of FIG. 3;
FIG. 6 is a left end view of FIG. 3;
FIG. 7 is a rear view of FIG. 3;
FIG. 8 is a right end view of FIG. 3; and,
FIG. 9 is a bottom plan view of FIG. 3.
The broken lines are included for the purpose of illustrating the portions of the badminton net base and environmental elements that form no part of the claimed design.