The ornamental design for a multi-head charging adapter, as shown and described.
FIG. 1 is a top perspective view of the multi-head charging adapter embodying my new invention;
FIG. 2 is a bottom perspective view of the multi-head charging adapter;
FIG. 3 is a top view of the multi-head charging adapter;
FIG. 4 is a bottom view of the multi-head charging adapter;
FIG. 5 is a front side view of the multi-head charging adapter;
FIG. 6 is a left side view of the multi-head charging adapter;
FIG. 7 is a right side view of the multi-head charging adapter; and,
FIG. 8 is a rear side view of the multi-head charging adapter.
The broken line showing of the lettering and numbering in FIGS. 1, 3, 5, 6, 7, and 8 is included for the purpose of illustrating environmental structure and forms no part of the claimed design.