First of all, thank you for your suggestions. I tried cleaning it some more, but no luck there.
Then i had the idea to stress test the laptop, in order to get an high power draw. If the connector is the Problem, then on high usage i should see the charging speed plummeting or even discharge of the battery. But non of that happened. I maxed out CPU & GPU, the Power draw according to HWMonitor was around 50W, but the laptop kept charging at the same rate of ca. 10W (i was at ~65% Batterylife).
My last resort would be to Update the BIOS, im on A06 and i found an A09 version on this http://bbs.xiaomi.cn/t-37742666 Chinese site. How do i Update the bios ? DOS-USB-Stick (and whats the best way to make one) and then run the .exe included in the .zip ? or simply run it in Windows ?
If that doesn't work as well i guess its an Charging-Hardware/Battery issue, so only an expert can help and that proabatly wont be worth it, the laptop was 550$ new and is 2 years old.
arki05 got a reaction from moriel5 in Wierd Laptop charging behavior / barely not charging