Thanks Stealthee. I had seen a youtube video from either Advance Auto or Auto Zone and they said you could bring your alternator in and they would bench test it for free, but nothing about testing your charging system while it was in the car. I may stop at one of those on my way to Firestone. If they tell me all I need is a battery I'll probably just buy the battery there. Of course, if there is anything else wrong, I'll have to get my car jump started to get out of there!