unfortunately I cannot find Specifications of the maximum possible voltage of the 5V IN port.
From the block diagram (https://docs.m5stack.com/#/en/core/m5stickc) it looks like that 5V IN is ACIN, is this right?
Refering to the AXP192 data sheet (https://github.com/m5stack/M5-Schematic/blob/master/Core/AXP192 Datasheet_v1.1_en_draft_2211.pdf) , up to 6.3V should be within the spec.
Is this right?