Question Laptop battery goes to 6%, then keeps working fine for hours

[sentenced06]

Hey guys, as the title says my laptop's (Thinkpad L460) battery is behaving in a weird way, it's discharging from 100% to 6% when unplugged, normally, it lasts for 3 hours at least, but then it's stuck on 6% and keeps working despite "your battery is running low" notification for 2-3 hours more. Depends on the load, while watching twitch/youtube it lasts less (3-4 hours in general), when idle or doing some light work it lasts for 5-7 hours. It charges back to 100% normally in ~2 hours, as it should be.

I tried recalibrating the battery via Vattage app, charging-overcharging it fully for few times, setting BIOS on default, resetting BIOS CMOS battery, installing W10/Ubuntu, nothing really helped, or it just helped a bit with "real" battery life display, but it's still the same behavior (battery goes down to 6% or 2% and then laptop keeps working for hours while being in "low battery" mode).

What can it be then? I wanted to swap the battery, but what if it's faulty charger, or MoBo on laptop itselfor anything else? I can't tell if this battery is genuine or fake, maybe you guys help me with that as well.

 

[sentenced06]

After posting this ive actually realised ive never tried another charger, only default Lenovo one, so I tried baseus 65w + adapter i had lying around, and started recalibrating thing again, it's been 5 hours and it still shows 20% battery (laptop is discharging itself, it's like step 1/3 of recalibration in Vattage), so it's a progress I guess?