I had a similar problem on a different model device after an upgrade. I finally fixed it by performing a Wipe Cache Partition, then powering off the phone, plugging into a wall charger (do not use wireless Qi charging for this step) and let it charge until completely charged back up PLUS at least two hours longer. Preferably charge it all night while powered off. This recalibrates the battery level monitor in the phone. Worked for me.
Not a reply but a question. I just ordered the Galaxy S5 and in researching I see that this Lollipop update is a pain. Do you HAVE to update that? Can it be avoided?
You don't have to, but you better be careful when that pop up comes up asking to install now or later. The repair patch will come one day soon we hope.
I just ordered the Galaxy S 5. Is it mandatory to update to Lollipop? I was researching and found this was an 'issue'....