extra battery strain

Im doing a large media system in my car that is gonna be used at my store for demo purposes and I need to run this with the car off for quite a while and I need to know, If Im gonna add a single battery with an Isolator, what kinda trouble am I gonna run into with my altenator being that it is only  a stock alt on my swift. I am not running a large stereo system with this, just a single 12 and a set of 6 4 tweet up front, but its still gonna be a small alt. Also, what kinda systems are people putting into there vehicles to plug them into the wall, are they just using a standard power supply or what?double-secret reverse-osmosis speaker-cone-induced high-level interference distortion, Its a killer

I've seen dealerships use a standard battery charger to display TV systems, although if you have a stereo system, I don't know if the charger will keep up.

I havent figured out the total draw yet but the video looks to be about a 12-15 amp draw and the stereo has a fuse rating of 40 on each amp and then the deck at 10 amps and the preamp at like 3. With all that going I dont see the battery charger doing it, I could mabye use a booster but I would rather have something that I can install in the spare tire well if possible.double-secret reverse-osmosis speaker-cone-induced high-level interference distortion, Its a killer

You could use one of those big power inverters used for display boards, just have an ac plug under the bumper to plug into a wall.2003 Chevy Avalanche,Eclipse CD7000,Morel Elate 5,Adire Extremis,Alpine PDX-4.150, 15" TC-3000, 2 Alpine PDX-1.1000, 470Amp HO Alt.