Someone told me yesterday that you can see battery degradation with 'acpi -V'

Battery 0: design capacity 1855 mAh, last full capacity 347 mAh = 18%
Battery 1: design capacity 2179 mAh, last full capacity 147 mAh = 6%

so yeah that explains the atrocious battery performance on my old thinkpad hah (Framework is still 100% of course)