Have 2 dentical ipads-Comparing Batteries-Have ?

[popeye]

I bought 2used ipads and want to keep one. They are 16gb wifi. I charged both to 100% and running a video on the browser. After 10 minutes one is at 97% and the other is 100%. The one at 100% is built in March 2010 and 97% built April 2010. The April one has 8 days left on warranty. Looks like a 3-4% difference so far.
Is this a good way to determine the battery?
Are there any other tests I can run?
I do have the same apps running with the double click.
Advice and info appreciated, thanks!
PS-anything else I should compare to pick which one to keep???

 

[Tim SPRACKLEN]

It is very difficult to compare batteries in this way because, unlike say a car's fuel gauge, the iPad's battery gauge recalibrates itself every so often to account for the ageing of the battery and other factors. This is why Apple recommend running the battery completely down every month or so. By doing so, the battery electronics can 'see' how the battery is performing and can adjust the percentage figures that it posts on the iPad's Home screen.

The differences that you are observing here could easily be due to a difference in the calibration parameters used by the battery software in the iPad and might not indicate an actual difference in the performance of the battery itself.

Tim