Almost all Surefire illumination tools are powered by 123A lithium batteries. In fact, we pioneered the use of these compact, lighweight, energy-dense devices in flashlights. We use them instead of standard alkaline batteries because of their many advantages, such as:
Higher Power Density
For a given size (battery volume), It would take two alkaline batteries to match the power output of a single SureFire 123A lithium battery.
For a given size (battery volume), Lithium batteries weigh about half as much as alkalines but produce more power.
SureFire 123A batteries generate 3 volts. Alkalines, just 1.5 volts.
Better Voltage Maintenance
A lithium battery maintains fairly constant voltage for up to 95% of its life, depending on discharge rate. At moderate to high discharge rates, the voltage of alkaline batteries drops rapidly, making them unsuitable for use in high-output flashlights.
Lithium batteries can retain up to 90% of their original power output capability after 10 years of storage, making them perfect for emergency preparedness use. Stored alkalines deplete themselves much more rapidly.
Wide Temperature Tolerance
Lithium batteries greatly outperform alkalines over a wide temperature range, providing a working output from -76° to 176° F (-60° to 80° C).