@Rasmus I had the same issue a few days ago when my Halo arrived. What helped fix it was to do an almost full cycle on the battery (unplug from mains, put a movie on, roughly two hours in I got the battery low warning), charge it full again, and attempt the update after a reboot. Though the whole minimum battery for update thing is ridiculous when the device is connected to an external power source. Especially the 50% minimum - it's usually 20-30%, and for me, even this update (~800MB in size) was quite quick, from update start to reboot into usable state it took maybe 8-10 minutes.