[Al Skierkiewicz]

The CBAII and now the CBAIII have the ability to chart and compare battery Amp/Hr ratings with the manufacturer's specifications. One thing that is invaluable is the ability to store curves for batteries from each test, even if years apart. This type of testing allows you to track battery trends, cell capacity and internal defects due to misuse, manufacturing, and end of life. While we do not test every battery prior to each competition, we do make some comparisons each year and certainly check all new batteries when they arrive. It is not possible to predict battery life for a specific robot in any match as there are far too many variables within a match. The battery testers do a fine job of checking suspect batteries and can specifically show when one or more cells have reduced capacity or are damaged in some way. The end of my electrical presentations show a family of curves comparing healthy and defective batteries. If your battery meets or exceeds the manufacturer specification then at least you know that the battery is capable of providing the same amount of power as the other guy's.
While gel cell batteries had certain indicators that they were aging (weight for instance), the AGM cells we now use do not. Often AGM cells will fail due to mis-handling such as dropping on a corner or lifting by the wiring. As the batteries age, non-conductive material will build up on the plates in the normal course of charge/discharge. This is the cause of gentle reduction in the capacity. However, our use is often times destructive in that high currents are demanded over short periods of time. I believe this causes distortion of the plate material due to the high temperatures encountered during the discharge. some teams have experienced actual cell shorts that cause high heat without load and distortion of the case.