Car Stereos: wiring amp to separate battery, alternator, amp

Question
I'm thinking of wiring my amp directly to a separate battery(no alternator) and i was wondering exactly how to do it and how effective it is.

Answer
Stephen,  If you wire to a separate battery with no alternator connected, you are going to lose power fast.  Your stereo will probably work for about an hour, then start to fade out for the next couple of hours.  I don't see it lasting over three hours on a single charge.  If you want to take some of the load off your current battery, you need to upgrade your alternator.  Hope this helps, Scott