By A at the end you refer to 16GB storage version?
i have 64gb version and use it balanced, high gain mode activated. it depends on the headphones and bitrate too, also volume, bluetooth and screen usage. i listen with hifiman re2000 iems and from time to time with denon d7200, these are big over ear closed-backs, non-balanced. with FLACs most of the time, i would say the battery is average, maybe 10-12 hours, but didn't pay attention, it's good enough, i charge it once a week or each 4-5 days, few hours each day of listening. I sometime use it as usb dac and also keep the screen on more than necessary. So there is no definitive answer but if your headphones don't require lots of power, you'll probably be satisfied.
Hello! Yes, I was referring to the 16GB storage version. Nonetheless, thank you for your reply and also the detailed information.
It was stated on Sony's website that the ZX300 would last up to 26 hours with FLAC. However, they didn't mention for balanced. Your answer is very useful. I'd like to know if someone else whom owns the ZX300A is the same as well.