The 4SR44 / PX28S silver oxide batteries are an ideal replacement for the PX28 mercury battery. It not only has a higher power capacity than an alkaline battery, but it also has a much more stable discharge voltage over the life of the cell.
Advantages of Silver Oxide Battery over Alkaline Battery
Higher Power Capacity (1.5X+ Power Density)
Stable Voltage Output
Superior Leakage Resistance
Lower Self-discharge Rate
Lower Internal Resistance (Perfect for film cameras that have incandescent lamps and magnetic shutters)