Keane had six teenagers on the field at one point, including Troy Brown, Tommy Smith and Shane O'Connor, and saw David Norris score Town's goal after a Deon Burton brace for the Addicks.
Keane told the club's official website: "I thought all the young players did well and I was very pleased with them.
"We have a lot of injuries so we had to mix it up a bit and throw some youngsters in against a decent Charlton side who were playing in the Championship last season.
"It was a big test for some of them, a learning curve, but you only find out about them when you throw them in and I was pleased with their response.
"Shane probably sees himself as a midfielder but he filled in at left-back with Damien Delaney injured and he showed a great attitude and desire."