Former Foxes forward Kermorgant scored twice against them last season and he repeated the trick here to add to Michael Morrison's early opener.
Despite Danny Drinkwater's strike Charlton held on to secure a 2-1 win.
Powell said: "I'm pleased for my group of players. They have been down and it is tough start but I told them there was no need to panic.
"We've had a lot of soul-searching between us all, a lot of hard work of the training pitch and changed our shape which has worked."
He added: "When Yann plays like he did here then not many strikers are better than him.
"I'm going to tell him there are 23 other teams called Leicester.
"He is good in the air, on the ground and he sees other things people don't.
"He has now played against them three times and scores three times. It is pleasing for him as he had rough time there.
"I was there with him as a coach so I knew he was a good player and that's why I brought him in. It was a good day for him and us."
- Sports & Recreation
- Danny Drinkwater