Why isn't my Lumia 920 battery bar updating under charge?

[Windows Central Question]

since some time battery bar doesn't update when phone is under charge.
in other words, bar do works during the normal use, showing decreasing level, but when i put the mobile under charge % doesn't increase.
That causes at some point the phone to shut down, as if battery would be gone, but then, if i start the phone, it shows the real battery level.
this means charge do happens, but it is not shown.
any idea about it?
already performed a complete software restore but it seems with no result

 

[RumoredNow]

Re: lumia 920 battery bar not updating under charge

Sounds like the chip in the battery might be going bad...

If you look at YouTube you can find some 920 teardown videos and on Amazon, etc, you can get tools and a replacement battery if you want to try DIY repair... Or visit a repair shop online or by phone and get an estimate... Or maybe think about upgrading from your trusted friend to a new phone...

Reasoning: Software restore didn't solve the issue, must be hardware and the smart battery is the most likely culprit.