I guess it easy.
Open the case,replace the cells,calibration, a new battery pack is back~~...but looks like it's hard to open the case unless you break it.

When you disassemble the laptop to replace the fan, you can double check the P/N or FRU number on the old fan and while you're at that stage, check and note other parts/components FRU & P/N in case of future replacements. Mine has FRU 44C0557. i found one from here : http://www.waresphere.com/store...