battery life and bit rate

Hi everyone,

I usually read the forums but now have a question of my own.  When I first used my clip, I only got a battery life of about 10.5 hours.  That was playing mainly 128 kbps wma files.  During my second “run”, I played more 96 kbps songs and got just under 13 hours.  Is there any relation between bit rate and battery life, in that a higher quality song requires more juice to read and play it?

A secondary concern is that that last 1/4 of the battery life, as indicated on the oled, doesn’t last very long (1.5 hours or so).  Does anyone else see that as well?

I’m thinking of returning my 2 gb clip and waiting for the 4 gb version, which looks fantastic.


Battery life varies, depending on usage. The bit rate does seem to impact the battery life. As for the 4 GB unit, that’s pretty much the only difference, & it’s silver. Same features, same battery life(average of 15 hrs)… I suggest saving your money unless you really want the extra capacity. I wouldn’t say your 2 GB unit is defective, so don’t return it… enjoy it :slight_smile:

Yes, bitrate matters. The higher bitrate you encoded your songs, the more CPU it will eat when decoding. We all have to find the compromise between sound quality, storage size, power saving (bitrate matters to both).

Thanks for the responses.  I can see that higher bitrates definitely require more power consumption.  I have done some reading online and sites such as cnet claim that wma drains battery life more than mp3 does.

I also remember seeing that certain sansa products have specified battery lives under conditions of playing 128 kbps mp3 OR 64 kbps wma, as listed.  That would mean that for any given bitrate mp3 allows better battery life.

Right now I’m testing my 2 gb clip and currently have a total of over 15 hours of playback on one charge, and the 25% full indicator just recently appeared!  I expect 16-17 hours total (~40% volume, occasional but infrequent screen/control usage).  This is compared to 12-13 hours with wma tracks.  I thought this might be helpful info for anyone looking to extend battery life.

Message Edited by tdc84 on 01-14-2008 03:03 PM

This post gives a breakdown of the bitrates I have on my clip and with which I got 16+ hours of playback:


In addition to bitrate,  the choice of the decoder and DRM affects the battery life.  MP3 format gives about 20% better battery life than WMA at the same bitrate.  Also, Protected content takes more CPU cycles.

For example:

16 to 17 hours is possible with MP3, 128K bitrate

10 to 11 hours is possible for WMA 160K,  protected  (Rhapsody Content).

I just wanted to follow up with everyone that I obtained 18 hours and 49 minutes of battery life using only 128 kbps mp3 files.  8 of those hours were overnight (no screen/button use), but I think this is very encouraging. 

I was concerned but now can see that the battery life really depends on bit rate and mp3 vs. wma.  I expect that with much more frequent menu use the life would be maybe 17 hours or so.