Ok...found a link for the battery voltages..
http://www.squidoo.com/kindle-battery
Seems like its full at 4.2V and battery cuts off between 2.7-3.0V. If its under 2.5V it has become unservicable. hmmm...not absoluetely sure, but could be mine was below 2.5V on some of the contacts before using the wall charger...