Powell told the club website: "I'm very pleased that Alex has joined the club.
"He's a coach and a man whom I not only admire but I know the players and other staff will respect and like as well, and he's a great addition."
Damian Matthew will step up from development coach to become first-team coach while Keith Peacock, who took caretaker charge of Charlton before Powell was appointed, has been named technical director.
Powell added: "I'm delighted with the team we've got in place. We're going to be working together very closely and we can't wait to start to get this club moving in the right direction again."
Source: BBC Sport
Source: BBC Sport