Speaking of 80% we saw an anomaly yesterday. We have the timers set to finish charging at 7am at 100% on weekdays and 80% on Sat and Sun. The car was driven on Saturday, then plugged in and presumably charged overnight to the 80% level by Sunday morning. The car was not driven at all on Sunday, so early Monday morning it charged the rest of the way up to 100% - but it didn't quite get there according to the SOC meter - charging had stopped but it was one bar short of full.
White 2012 SV delivered 10 Dec 2011 returned 25 Nov 2014 replaced with stopgap ICE Sentra
[35 months] [35K miles] [9 Bars]
2013 Volt replaced after 36 months/30k miles with ICE Rogue
2016 SV-adjacent May 2016 lost 4th bar March 2018