Macbook 7.1 (mid-2010): upgrade from 10.8 to 10.12 I've tried several times to update my Macbook 7.1 (Macbook white mid-2010, 4GB ram)  from 10.8.5 to Sierra but the progress bar remains blocked after the first boot.

When booting into Verbose mode, here is what I obtain: 

After a while, I have other messages like:

SmartBattery: finished polling type 1
SmartBattery: finished polling type 4
SmartBattery: finished polling type 4
SmartBattery: finished polling type 2
SmartBattery: finished polling type 4
SmartBattery: finished polling type 4


Which seems to be the same issue than:
Mac Sierra won&#39;t boot - SmartBattery: finished polling type 4
Two solutions were kindly given by Allan, I chose the "easiest" one: 


In recovery mode, access to Terminal
In /Volumes/"Macintosh HD"/System/Library/Extensions directory, remove Huawei .kext files (using rm -rf command) or other non-essential kext files. It appears that, for some reason, many users had issues with Huawei kext files...
After reboot, the installation was completed seamlessly, Sierra is finally installed.