lost in an abyss of focus frustration!!!!>(

hey guys i need some serious help.....i bought a used ford focus from 01 nice car but i've taken it to the shop like 5 times since i got it....i seem to have a problem going from the battery to the cd player..cuz everytime there is a cd player connected or radio it drains the battery, when i un plug the cd player the car is fine but as soon as i hook one up the battery drains over night.... can anyone help me... i'm lost in an abyss of frustrations!