but what really matters is they are lithium (high current). not the cheesy alkaline types.
One thing to consider is. You may measure 1.5v/cell when idle, but if you don’t have enough current (e.g. alkaline) then your voltage will drop some when under load.
you should ask more specific questions like for what diodes and drivers.
i run 1 of my blu rays and one of my open can red at about 11 volts (3x10440) and a rckstr driver.
1 blu ray with 6 volts with a groove driver
and the other two blu rays at 4.5 volts on flex drive drivers.
I have a blu ray 4.5v with flexi driver (2xaaa)
blu ray 12v with rckstr driver (3x10440 3.7v)
blu ray 9v with DDL circuit (9v battery)
sony and lg open can. 7.2v with rckstr driver (2xcr123a 3.7v)
also a red laser module which needs 5v, I stripped a usb plug and it's computer powered now .