I can check the IR of my battery without it being charged. I hold down a button and it takes 5-6 seconds to show my IR.
I am not an IR guru or anything. I just know the lower the number the better. However, I'm not sure what all affects the reading. Would longer/shorter cables give you a different reading? Would thicker charging cables give you a better reading? I need to play around it with it more to find this stuff out.