y do you need one?
does it run hot?
fans on hight all the time ?
check you cpu usage is it 100% <happen to me had a virus hog all cpu killed battery and ran super hot>
also take the covers off on the back eg memory hdd cpu cooler WHEN PC IS OFF! and hover put all the dust form inside case check fan holes and hover.
you may find you just need to do some house keeping!