Dell Latitude e6230 with i5-3320M, , original Dell AC charger 65Wh 19.5V 3.34A, original extended 6-cell battery 65Wh 11.1V.

Laptop charges until 25% and then it starts to idle (25% available, plugged in). When connected to AC, it occasionally starts to charge for 2-3 seconds and then stops. Problem persists in both clean Windows 10 installation and Arch Linux. When laptop has 25%, it is shown that 3-4 hours left, so I think the problem is wrong calibration of battery. However, I couldn't recalibrate it.

Battery health is 81%, "good" state, so it is far away from considering as "dead". Both battery and AC charger are recognizable by system and bios. Bios and all drivers are updated using Dell site and Bios set to it's defaults. SupportAssist reports that everything is fine.

Update: now it's stuck on 26%. Yesterday it was stuck on 43, then 44%.

I'll be glad to provide any required info. Thanks in advance.