You Do Need power plug adapter while traveling from Benin to Ghana.

Here is Why You Need An Adapter

The outlet and plug type used in Ghana are D and G and in Benin are C and E. This is how they look like.

Benin

In Benin, outlets of type C and E are in use.

Type C

Type E

Ghana

In Ghana, outlets of type D and G are in use.

Type D

Type G