Yann Kermorgant scored the only goal of a match dominated by controversial decisions from referee Trevor Kettle, who showed a straight red card to Charlton captain Danny Hollands for his late tackle on Kieran Lee and also sent off Oldham's Jean Yves M'voto for two bookings in the first 41 minutes.
Charlton winger Scott Wagstaff was dismissed for a second caution in the 76th minute, while seven other players went into the referee's notebook.
Powell's side, however, remain six points clear at the top of League One and he said: "You have to applaud every one of my players. Nobody could doubt their attitude, their character or the commitment they showed to each other, to me and to the club.
"It was some game with the number of cards, but it wasn't violent at all. I know referees have a hard job and need to get hold of the game early on, but when you give out early bookings you set a precedent for yourself.
"Danny Hollands did catch their player, but it wasn't studs-up or knee high and it wasn't a sending off. The Oldham player didn't deserve his second yellow and, for our second sending off, Scott Wagstaff slipped and their lad went over him."
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