Charcoal was created only a few years before the war and lived with 2 siblings, Acidtrip and Deadeye. Until an incident happened that caused the sisters (Charcoal and Deadeye) to abandon their younger brother.

Charcoal used to and continues to mine for Energon and certain metals deep under Cybertron's crust. This in turn basically isolates herself from the surface and the conflict that's happening on it, and she wouldn't have it any other way.