New Brazilian signing Geovanni made his first appearance for the club alongside Rolando Bianchi up front, while Danny and Matthew Mills were given a go in the City defence.
Shaleum Logan was given another chance to impress in a youthful City midfield which featured fellow Academy graduates Michael Johnson and Stephen Ireland.
The home side took the lead with a 20th-minute penalty, awarded against Matthew Mills for a push in the area.
And the 21-year-old defender's night got even worse 15 minutes later when he was outpaced by a Charleroi forward on the way to laying on his side's second goal.
Matthew Mills was replaced by new signing Gelson Fernandes at half-time, while Bianchi and Geovanni made way for Bernardo Corradi and Georgios Samaras.
Samaras went closest to scoring for City in the second half, hitting the bar with a left-footed strike in the 53rd minute.
Another second-half substitute, Ishmael Miller, also went close for City, who will now turn their attention to Wednesday's friendly against Shrewsbury at the New Meadow.