The 22-year old Italian striker, who joined on loan from Manchester United in late January, opened the scoring for the Brum in the 22nd minute when he produced a glancing header to a cross from Manchester City loanee Emyr Huws.
With just over ten minutes remaining, Macheda doubled Birmingham's advantage when he raced onto a neat pass from former Norwich City midfielder Tom Adeyemi to slide past Charlton keeper Yohann Thuram-Ulien who is on loan from Standard Liege.
Macheda now has three goals in two outings for Lee Clark's side after netting in the 3-3 draw with Derby County last weekend and his performance was not lost on his boss who was grateful to United for the loan.
"I only hope they don't do so well and they then (have to) go back early."
Birmingham's victory over Charlton allowed them to remain 18th on the Championship table and pushed them nine points above the relegation zone.
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