Ok, so in my humble opinion, the Sansa Clip series are the best music players on the market. They support a wide range of formats out of the box, like Ogg, Flac, Wma, Audible, etc. They run Rockbox. They are light and have an affordable price tag.
They only have one major flaw: battery life.
The original Sansa Clip Zip battery had just 300mAh. (the original Sansa Clip had 330mAh) On top of that It would lose 2/3 of it's chare in just a matter of days of lying around without being used !
Enter: My brocken previous Phone's 1000mAh Battery.
Yes, it was that easy. All I had to do, was replace the Sansa Clip Zip batterie with the Nokia one.
It was even beautifully labeled: Plus to Plus. Minus to Minus. N to Unmarked.
Obviously the Nokia battery is just a tiny bit larger than the original Sansa one.
With a bit of sawing and filing I opened (read sawed away) the sides of the case and was thus able to squeeze the battery between the two halves and secure them with double-sided adhesive tape.
Last but not least, I finished it off with a bit of Sugru. The result may not win any design awards, but it works. Very well. Or should I say long.
As an additional bonus, with the battery extending the length of the player, the 5 way button is now in the effective center instead of the bottom, making the buttons more comfortable to press.
Update: Running time is now 30 hours and 32 minutes. Measured using Rockbox firmware. After fully charging the battery I let it play a continous mix of mostly highquality mp3 with a good helping of ogg, wma and flac media thrown in. Media was mostly played from 32GB microSD and some from internal flash.