In anticipation of a two hour show coming up that I plan on shooting with my AX-100, I bought the following two items:
And then did a little test where I fully charged the new battery and shot video at the highest quality setting (UHD 4K XAVC S 3840 x 2160p / 30 fps / LPCM audio) until either the card filled up or the battery ran out of power.
The battery ran out of power before the card filled up. So I then filled up the card using the OEM Sony battery that came with the videocam.
first file: 2 hrs 47 mins 39 secs (116,156,563) shot using the Wasabi Power battery
second file: 14 mins 41 secs (10,185,380) (using the OEM Sony NP-FV70 battery)
So at the highest quality setting, I was able to fit 3 hrs 2 mins and 20 secs of video on the 128GB Sony card. Note: even though the camera stopped at the point where the battery ran out of power, the first file was unaffected and plays all the way through to the end (using VLC on my computer).
I got the Wasabi Power BTR-FV100-JWP battery (replacement for Sony NP-FV100 - which costs $124.00 at Amazon) for $15.69 & free shipping at Amazon. I got the 128GB Sony card for $64.99 & free shipping at Amazon.
This was a static video shot with no moving objects in the picture, no zooming, or any other activities that would decrease the life of the battery.