The first two models of F-1 (the F-1 and F-1n, both before the 1980's) will accept a modern 1.5V 625 type cell and if desired you can have the camera meter calibrated to use these as opposed to the calibration the camera originally had for a 1.35V cell.
You can also use a modern Duracell 386 silver oxide 1.5V cell in an MR-9 battery adapter to drop the voltage to the 1.35V to power the meter. This requires no meter recalibration.
The third F-1 model (F-1N aka F-1 "NEW") from the 1980's uses the presently commonly available 6V PX28L model of battery.
Keep in mind that for best "convenience" of operation, the "NEW" F-1 should use the FDn ("NEW style) lenses, with the dual-aperture-rows on them. The "NEW" F-1, however, WILL work just fine with the older style breechlock-ring lenses, you just lose the ability to see the lenses aperture ring in the camera's viewfinder in one of the camera modes. Overall though that is no big deal.
