Re: Two batterys
First check you alternator belt and make sure it doesn't slip. Turn off the motor, grab the alternator fan and try to turn it by hand. If you can turn it using minimal or moderate force then you need to tighten or replace it.
Make sure your battery is fully charged and tested. If you don't have a battery tester then visit your local sears or any place that sell batteries. A low or bad battery will not allow an accurate voltage check of the charging system.
Start your engine, the voltage should be at around 13.5 - 14v when you're at 3,000 rpm. If it's still at 12.something then you have a problem in the charging system.
As for the current used by your accessories, it's a complicated test that requires an amp meter. Best to go to an auto electrician for this. But in my opinion, you have a charging system problem.
I would not recommend putting another battery in you car. More components means more that can go wrong!