issue with battery or battery management system, missing 20%

I have Opel Ampera 2013, 90.000km / Chevrolet Volt

ssue with battery or battery management system:

Wheen charging battery to full:

1. everyting is O.K. until around 80% SOC-U approx. 1.5 hour to complete charging
2. around 80% SOC-U electric current drop under 1kw (16A charging station)
3. SOC-U % stops at 80% for approx. 20 minutes
4. in 1 second, SOC-U jump from 80% to 100% (Fully charged) > 1.5 hour before expected (Fully charge), when normal condition need 0.5 hour more time than expected.

Youtube movie 20:04 moment when SOC-U jump from 80% to 100%

youtube.com/watch?v=_0qJPRzMAkg&feature=youtu.be

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When driving with 100% full battery:

1. first 2 km (downhill) I use 1kw, where normal use is 0kw (1 year, same everyday)
2. next few kilometers on flat road I use anoter 1kw (sum=2kw), where normal use is 0.6-0.9 (1 year, same everyday)
3. when Soc-U is bellow 70%, consumption (kw) become normal as expected

Normal 1 year average result for 18km long distance (drive every day):

Summer - 1.9 - 2.4 kw
Winter - 2.8 - 3.4 kw

Now - ideal condition, 100% battery) with issue: 4.0kw
Now - ideal condition, 60% battery) with issue: 2.0kw

Range 45km - 55km, before issue 65km - 75km
Computer consumption after gas engine starts is around 9.9kw - 10.5kw most of the time, when I spotted issue for the first time it was around 8.0 for 3 or 4 rides.

I was on service to check state of battery, computer did not show any errors.

Does anyone seen this problem?