Pry up main board gently by lifting the Fan end of the motherboard.

pull board gently toward the fan end to dislodge the connectors from the case and release the main board.

when released, turn over the board to view backside of mainboard.

RTC battery can now be replaced.

Functional RTC voltage is above 3,1V.

Brand new RTC voltage is 3,3V

recommend to tape down loose connectors away from main board while assembling the main board.