No that would be far far worse test than having 2 equivalent batteries, and discharging one of them. First, it is easier to measure differences than absolute va

No that would be far far worse test than having 2 equivalent batteries, and discharging one of them. First, it is easier to measure differences than absolute values (by eye, but even with precise equipment), second it automatically cancels out the affects of temperature, humidity, pressure etc. (Okay, you know that these things doesn't matter in this experiment, still.)