Manager Keane told the club's official website: "I've been alongside 'Charlie' on a couple of coaching courses and he left an impression on me there.
"He's got a lot of experience, knows the league inside out and obviously has managed as well, at Notts County.
"He's a bubbly character and most importantly, he's a good man. I've always kept an eye out for good people with a view to adding to my staff here and Charlie is someone I can trust. I'm looking forward to working with him here."