i don’t do proxmox; but i do a lot of virtualization through kvm/qemu on my own laptop and the battery can take a beating if you don’t mitigate it somehow. i’ve had this laptop less than 6 months and the battery condition is already at 67%.
i’m lucky in that i got this laptop from a linux company so i can can order replacement batteries; but most people don’t (willingly) have this luxury anymore.