Egyptian forward Gedo scored in the 33rd-minute as Charlton failed to fire during the opening hour against Steve Bruce's men.
Charlton began to find their feet in the closing stages but it was too little too late for Powell's team.
He said: "We didn't start off the right way and we paid the price with a poor goal.
"But we gradually got into it and soldiered on. I asked for a response at half-time and I got that.
"The save from David Stockdale from Danny Haynes (was vital)...that could have got us something out of today."
He also praised a Hull side who have now won three games in four.
"We played a good team who play a certain style but we managed to quell that at times," added Powell.
"They're a confident side who are going well and we knew it would be a difficult task over 90 minutes. But for a relatively inexperienced team we certainly played our part."