I have a number of extra batteries for my HVxx:es with different capacity and each in different state.
I find it often frustrating to find out unexpectedly that the battery in my camera is near to it its end of capacity when I have no spare time to change battery.
One way is to solve this problem is to rate the batteries and run each battery fully charged in the camera in recording mode with active display until it is fully uncharged and just note the minutes it can run on a fully charged battery.
Then you know when you pick up a battery in your backpack the expected number of running minutes that you could expect.
Does this make sense or do you have any better idea to keep track of the capacity of your batteries ?