Well Matt Sorry that I have only been an operations director at several aerospace firms, including General Dynamics and Litton, which included responsibility for test and calibration labs. Apparently, my aerospace experience doesn't match your education. Oh, did I mention that early in my quality engineering career I performed product audits on spacecraft that landed on the moon? With that background, how could I possibly know anything about something as simple as a lead-acid battery?
If you want to learn something, instead of just arguing, pay attention to the post by DougW above. Pay particular attention to the discharge curves which show clearly that battery voltage DROPS as it discharges.
Dick