The ornamental design for a usbcarcharger, as shown and described.
FIG. 1 is a front view of the USB car charger, the rear being a mirror image thereof;
FIG. 2 is a right side view thereof, the left being the mirror image thereof;
FIG. 3 is a top view thereof;
FIG. 4 is a bottom view thereof;
FIG. 5 is a front, top, right side perspective thereof; and,
FIG. 6 is a rear, top, left side perspective thereof.
The broken lines showing of the rectangles on the right and left side are for the purpose of illustrating the location of the USB ports on the article and form no part of the claimed design.