[Al Skierkiewicz]

Win,
The internal resistance of the battery will vary with temperature, state of charge, how long it has been off the charger, age and how many times it has gone through a charge/discharge cycle. While the Beak is a good check for battery condition, you likely will get better data with a different test method. Nothing beats a Beak in your pocket to know you are ready to play with a known good battery. If you are trying to check against manufacturer's spec, you must test under their conditions. The stated test data varies from manufacturer to manufacturer which is why the MK battery and Enersys are rated for different amp hour capacities when they are identical batteries.
I recommend the CBAIV from West Mountain Radio which happens to be located close to you. While the test takes a couple of hours for each battery, it allows you to overlay tests and print results. It will display real time amp hour capacity throughout the test and then store the results. You can vary the load up to 150 watts which allows you to set the discharge rate to match the specifications or to increase the discharge to simulate robot conditions. One of the best parts of this tester is the ability to see if individual cells have reduced capacity and if there is internal arcing due to damaged plate connections or inter cell wiring.