French defender Dorian Dervite has a new deal which keeps him at The Valley until June 2014, while young player of the year Callum Harriott has agreed a three-year contract.
Dervite began his career with Lille and has also played for Tottenham and Villarreal before being handed a contract by Powell after impressing on trial last season.
The 24-year-old scored three goals in 31 appearances for the Addicks last campaign, some of them coming in midfield after he was drafted in as emergency cover in that position.
Harriott secured a regular place in the Charlton team towards the end of the season, scoring two goals in 14 games and he admitted he was thrilled.
"I'm absolutely delighted to sign a new contract," the 19-year-old told the club's official website.
"I'm overwhelmed. It was a fantastic season for me and it's great to agree a new deal. Charlton is a great club - I enjoy it here and I love the supporters.
"I'm already thinking about next season, and I want to stay in the team and keep playing as many games as possible."