Just completed my NW-HD5H battery test to compare performance to my previous NW-HD1. Sony claims that the NW-HD5H can achieve up to 40 hours continuous playback with the lowest bitrate of ATRAC compression. The NW-HD1 was claimed to play for up to 30 hours. When I tested my NW-HD1 I decided to perform the exercise with the remote connected. The unit achieved 27.5 hours continuous play on tracks encoded at ATRAC3plus 64K so I was pretty pleased with that. So bearing in mind the NW-HD1 achieved over 91% of the stated potential, I was looking for around a massive 36 and a half hours from the NW-HD5H under the same testing conditions. Well the unit played for a pretty impressive 35 hours 10 mins which I reckon is excellent. And the fact that you can replace the battery relatively inexpensively once it starts to degrade is the added bonus. My players now getting some well earned "juice" as we speak. EDIT - For those interested in what this means in thhe context of number of tracks played it was 531 at an average length of just under 4 mins a track. If you put an average album length at say 12 tracks then it would allow the continuous play of over 44 albums - pretty good. It should be noted though that this test was conducted with absolutely no operation of the controls during playback and so in the "real world operation" times will be MUCH shorter.