The Addicks had even opened the scoring with a 12th minute Rob Hulse strike before Jonathan Woodgate, Scott McDonald, Emmanuel Ledesma and Richard Smallwood replied for the visitors.
Powell said: "We started off the way we wanted to - it was a well taken goal by Rob.
"We got hurt by a couple of individual mistakes in the first half then we were chasing the game in the second.
"The scoreline doesn't really reflect what went on but they punished us in front of goal.
"You want to perform at home but also I think we can do better - there's more to come from the players but we haven't done that at home.
"We can't really dwell on it, we have to look forward to Tuesday and there's no better way of turning it around quickly."