Subwoofer install without power cables..?

This really isn't a good idea. You will need to tap into the factory head unit for the source anyway. The only part you would avoid by doing it that way is running a power cable from the battery in the engine bay to the amp. So for the hour or 2 to do that, you would rather charge a battery every night? Might as well just do it right.

yes you can use batteries in the cabin, trunk etc. just make sure you

use AGM batteries. they dont leak acid because they are sealed

and the acid is absorbed into glass mats. as for getting a signal u will

need a LOC in which you will have to tap into one of the speakers.

so u will have to modify the car somewhat. As for how many batteries

you will need to get 5 hours of play time... well im not a battery amp

hour guy, im sure someone else here could get you a better answer, but

im sure it will be alot. Ar least 5 group 31's AGMs to start. how long it will

play wll depend on how many amps ur amp will pull from the batteries

and how hard you push the subs.

you do know you can put in a proper system and take it out when your

lease is done right? its not like your car has those seals on it that

let manufacturers know its been tampered with right? I would just do it

the right way and just remove it when the lease is done. hope this helps

good luck