Under most ideal conditions i get about 20 hour playback. I did a little test. I let the unit (NW-A 3000) play all tracks with a full charged battery (mp3 VBR average birate 160 (Lame, R3MIX)) volume 23 and not move the player, the display on : six time 20 sec and with the harddisk 80 % filled. (about 20 hour playback) In daily use it is a lot shorter (Dit not monitor it yet), but for Sure shorter than 10 hours. If you want getting battery life like Sony's specifications, you must use atrac 48 and not move the player around, no shuffel, no EQ, and no use of the display. About the availability of the sony battery for the NW-A 1000\3000: I found no place where they sell this battery. Bruut