I've used it when fully charged but never run it down completely. I have the Sony CX230 Handycam, which shows full charge for recording at 6 hrs 50 mins, that's a lot of recording time. The size and weight actually makes the camera feel more substantial. It's comfortable to hold and adds some balance when zooming in, not heavy or bulky. I use this battery as my main battery and keep the original FV30 as backup, which I haven't needed so far.
The longest nonstop recording I've made so far is 30 mins, the battery still held almost 6 hours for recording. Playback obviously shows a different battery life, but it was still over 5 hours with the one charge.
Hope this helps.
Wow! Sony doesn't make it easy, I had to download the "HXRNX70U NXCAM Compact Camcorder" brochure to get the answer.
Yes, the Sony NP-FV100 battery will work in that camcorder according to their brochure.