SlimX 400 battery problem

[Y2Kwhat?]

What could cause the batteries supplied with the SlimX 400 to swell up after you charge them? The iriver website says it could be because they were plugged in the wrong way but that wasnt the case. Does anyone know of any other reason?

[neato]

Regular overcharging could be an issue since the recharger is timer based I believe. Could be a manufacturing defect of course. Thankfully never experienced the problem on any of the various SlimX's I've had.

[ECA]

yep, those are the main causes..