Thanks for the suggestion @Russ. I’ve done that just to be sure.
After a full-upgrade and a couple reboots, I closed the computer (which should’ve caused it to sleep), and left it over night for ~8h. Battery went from 96% to 56%.
I took the back cover off to investigate what was burning so much energy. It’s the RAM chips. They’re warm to the touch.
RAM is Crucial 16GB 260-Pin DDR4 SO-DIMM DDR4 2133 (PC4 17000) Laptop Memory Model CT16G4SFD8213
I’d very much appreciate any thoughts on next steps to diagnose this problem!