As the Addicks chased an equaliser following Radhi Jaidi's opener, referee Andy D'Urso correctly adjudged that an effort from Miguel Llera, which crashed off the underside of the crossbar, had not crossed the line.
"I've got to say, at the time I thought it was over by a number of inches," admitted Powell.
"But I've seen it on video and I've apologised to the officials because they made the right decision and it's a fantastic decision considering they made it in real time."
Charlton did eventually equalise, and avoid an eighth defeat in nine, through Saints old boy Bradley Wright-Phillips.
"Fair play to the boys as they showed courage after going a goal behind and we got what we deserved," added Powell. "It's been a real tough time for everyone, including myself, after coming in with four wins at the start. We put in a real shift."
Source: PA
Source: PA