KYORITSU 2413F - Manual (Page 21)

Replace the battery when B symbol appears on the LCD display.
(1) Set the function/range switch to the OFF position.
(2) Unscrew and remove the battery compartment cover from the rear
of the case.
(3) Install a new 9V battery of type 6F22 or equivalent observing
correct polarity.
(4) Screw the battery compartment cover.
― 19 ―
６．Battery Replacement
WARNING
Never replace the battery during measurement.