While I am not an electrically savvy student, my team the past year has conducted an extensive study of how the condition of batteries can affect robot and systems performance. This was after we placed seemingly healthy battery in the robot, and suffered many systems problems during a match due to the poor condition of said battery. The study can be found here on our website. This also includes descriptions of the tests we did and the information we found.
http://the-charge.com/uploads/3/3/5/...atteries.p df
I hope this helps.