Leon Legge struck in the 89th minute when he headed home Myles Weston's corner to put another massive dent in the Addicks` promotion hopes.
Charlton now lie 13 points adrift of the top six and have gone seven matches without a win, leaving their disgruntled fans to make their feelings known at the final whistle.
Powell said: "These players will learn that when things aren't going for you, that is when you find out about yourself and how you can make yourself better and play under pressure.
"That is what is happening to us now. Of course the fans aren't happy and that is expected but I want them to still believe in us and stick with us because they are important to us, as much as I'm sure we are important to them.
"They are the lifeblood and they are the club. We are doing our best to get out of this situation and I think they realise that things aren't exactly going our way."
Source: PA
Source: PA