The eletric chargers you see on ebay for like £20 are electric ducted fans, designed for model aircraft.
Although they can make a plane fly, they are axiel fans which can move a fair amount of air, but with NO pressure at all. They would not be able to make kind of boost on a car engine.
Electric super charging IS possible (just connect an electric motor to a normal belt driven charger) but the motor and power requirements would be huge.
Waste of time and money.