I just got the battery indicator working on my x280. I applied the x220 DSDT patch from here https://github.com/RehabMan/Laptop-DSDT-Patch/blob/master/battery/battery_Lenovo-X220.txt copied DSDT.aml into patched and deleted SSDT-BAT and SSDT-BATC. More by luck than anything else.
Thanks for posting about using the T480 EFI, it was a big help.