A recent article from Engadget.com has many Zune owners concerned about thermal expansion of the battery causing the Zune screen to crack. Although no photos were provided by Engadget, the article suggests this happens when the Zune is left charging overnight. To shed a little light on the subject we’ve taken a photo of the Zune guts from the side. The battery is clearly thinner than the hard drive.
The battery would have to undergo massive expansion to wedge itself between the rear housing and LCD screen. In fact the battery does not even touch the screen, it rests on the PCB. Another point to consider is that heating of Li-Ion batteries occurs during rapid discharge only (such as a short circuit), not during the charging phase. Finally, the Zune layout is based on the Toshiba Gigabeat which has no record of thermal expansion problems. If screens are indeed cracking the source of the damage is not likely from charging the battery. Until further information is available (such as a photo or a source) we call BS on the rumor.