A double from Karl Ahearne-Grant on either side of the break was enough to hand the Tykes, who sit 5th in the table, an away defeat in south London.
Addicks boss Lee Bowyer was left signing his sides praises at full-time: "“That’s our best performance.
“They’re the best side we’ve played so far. I’ve just said to the lads – that’s what we’re about. That’s the team we are. That’s why I got so annoyed when we lost the last two silly games. But we’ve put that to bed, we’ve got a clean-sheet. We’ve defended properly, like men, and it proves all that hard work isn’t for nothing.
“Everyone from Jed up to the front-two, it was a great team performance. If you’re going to get promotion, that’s what we need. We have everything in this dressing room, it’s great to watch. The way they fight for each other and do the dirty side. But they can play as well. It’s in their hands. If they want it, they can get it. Me and Jacko will keep pushing them. We won’t let them come off it. Today was a very good day.”