The win meant that the Londoners completed the double over the Foxes and old boss Nigel Pearson this season, and Powell was delighted by his side's performance.
"I've done the double over Leicester and my mentor and I don't know how to feel really. I'm pleased for my club and pleased for my group of players. We needed a result and they were made to work hard for it," Powell told Sky Sports News.
"It's huge because we had lost three games and drawn one in our last four. We've been playing well but we've just been getting hurt by late goals and a poor goal conceded at Hull on Saturday. It's fallen for us this evening.
"I'm really pleased for my players because they believe in themselves. I trust them immensely, they work really hard. You just hope that they can continue to build on that and we're just looking for consistency. I hope this is the start of a really good run for us."
Charlton now sit 12th in the Championship table.