i got a 3.6 volt Li-Polymer. it holds pretty long. about 4 days on normal use and a little over 16 hours on none stop Walkman 25% volume with java time to time.

charging is not an issue at all. just about an hour from 4% to 100%. an over night charge is over doing it.

i've had the phone with the battery from july 2006.

i used battery-discharge.jar for to get complete discharge.