The ornamental design for a batterypackadapter, as shown and described.
FIG. 1 is a front perspective view of a battery pack adapter in accordance with our new design;
FIG. 2 is a rear perspective view of the battery pack adapter in accordance with our new design;
FIG. 3 is a perspective view of the battery pack adapter as viewed from a bottom side in accordance with our new design;
FIG. 4 is a front elevational view of the battery pack adapter in accordance with our new design;
FIG. 5 is a rear elevational view of the battery pack adapter in accordance with our new design;
FIG. 6 is a top plan view of the battery pack adapter in accordance with our new design;
FIG. 7 is a bottom plan view of the battery pack adapter in accordance with our new design;
FIG. 8 is a left side elevational view of the battery pack adapter in accordance with our new design;
FIG. 9 is a right side elevational view of the battery pack adapter in accordance with our new design; and,
FIG. 10 is a front perspective view of the battery pack adapter in accordance with our new design illustrating a state in which batteries are attached to the battery pack adapter.
The broken line showing of environment in FIGS. 1-10 is for illustrative purposes only and forms no part of the claimed design.