Personally, i find the battery bar thing virtually useless. How about instead you display the estimated minutes remaining of play time? If you start with 10 hours on a full charge for example, count down from 600 - at zero it dies. This would be much more useful.
I think the issue of this may be that battery power remaining under this approach depends on many factors, such as volume level, player settings (e.g. backlight duration), user fiddling with the player, bitrate and codec, etc.
In my case, I have no problem with my battery indicator on my laptop because it indicates how many percent left and it also estimates the length of time I can use my laptop until may battery is drain 
