My battery died too. I then bought one of those aliexpress replacement batteries. And it was indeed very easy to replace the old one, at least after unscrewing all those little screws that hold the metall bottom of the notebook (20? or so). The new one has some 50.000 mWh and a running time of 3 hours 45 min according to BatteryBar v.3.6.6 (I did not test out whether the new one really runs that long as my notebook is normally in use only indoors).
