this is a stupid question because i think the question will prob be NO. Right now i am working on my car and want to listen to some music (no i dont have a portable cs player, just before some one suggests it) and was wanting to know if i would hook a battery charger up to the battery terminals and run the car of the house mains power so i dont kill my battary. just wanting to know if i will creat a big explosion?

Yes stupid question no need to remind me.

Cheers.

I suspect that to run stereos for shows, there is a transformer connected to the h/u, and run via the mains.

A large enough power supply will be fine. A 6amp power supply would run a basic head unit.
Car battery chargers are not made for power supplies. they have hum and ripple. ie: they're not filtered. so you'll be pumping in some AC noise.

However if your running a amp, you'd need 18+ amps if you like it loud.

Most people I know have the battery on charge when working on cars with the doors open, radio on etc.

na no amp, just a basic HU and speakers.