Hi,my n73 battery gets low too quickly,after only 20 minute of talktime.

Hi, the problem you are having is caused by the battery having bad cells all you need to do is get a new battery and your phone will be back to normal.

a little trick to remember:

every 6 weeks let the battery go totally flat let it go that flat that the phone wont even light up when you press the on button, then give it a full charge, doing this will prevent the build up of bad cells and this will then keep the battery in best condition,

let me know if you need further assistance ok