Finally, I did a comparative test of battery consumption for two firmwares - official and custom from Lurker.
Initial data:
firmware - 2.9.121 and 2.9.121-L0
firmware settings - reset to default
files - images of CD-rips CUE+FLAC compression 8
playback order - tracks of images by random
load - standard (2 * 32 Ohm) at the output of 2.5 mm
volume - 35 divisions (comfortable for me)
Compared with the previous test, conducted almost 11 months ago, the player was discharged a little less - 16 hours on the official and 16 hours 30 minutes on custom firmware.
The difference between the duration of work on the official and custom firmware is possible due to the unequal starting charge of the battery, although I tried to charge both times identically.
The discharge indication now starts not after a couple of hours, like the previous test, but almost immediately, that is, iBasso may have fixed their firmware (I wrote to them), but maybe not.
The discharge indication now has excellent linearity.
The fears of some users about the increased power consumption of custom firmware from Lurker were completely in vain - great work, master Lurker, go ahead!