Let me give a short thanks to Al and another plug for the CBA (computerized battery tester).
http://www.westmountainradio.com/pro...oducts_id=cba3
We've used this at his suggestion now for 3 years, and even gone so far as to rate our batteries 1-10 based on their tested capacity. It takes a while, but is definitely worth it to weed out the batteries that are simply worn out.