After Rob Hulse had given the Addicks a 12th minute lead, goals from Jonathan Woodgate, Scott McDonald, Emmanuel Ledesma and Richard Smallwood earned the visitors a happy trip to The Valley.
And the Boro boss said: "In the last 20 minutes we were impressive. Charlton had asked us a lot of questions the first hour or so.
"But we had six hours on the coach coming down, so I can forgive them the first 20 minutes.
"We got confidence by coming from behind against Bolton last week and I thought we finished the game really strongly but it was a bit harsh on Charlton.
"As we know from last season, when you don't win at home for a time it becomes more difficult - the team feel that."