the power windows are already up and you hit the switch to move the windows up some more. My headlights dim a noticeable amount. Is this normal? Or is the battery getting weak?

I'm concered because I'm about to upgrade all the speakers and put an amp and sub in my 02 coupe. Will I need to upgrade the battery too?

 

Absolutely normal. With the window motor stalled, you're throwing a 20amp draw at the electrical system - particularly while at idle.

P

 

This is normal but it is definitely more noticeable when you have a weak battery!! P.S. you battery should not have to be upgraded just b/c you are putting a system in your car. The only responsibility that your battery has it to start the car. After that is is up to your alternator to do the rest.

 

one of my friends had a similar problem, and when he put his system in, the battery died, he ended up putting in another battery for the system.