
Ok the one singular hemorrhoid-ial pain in the butt about the Vortex Sparc red dot is the goofy CR2354 that no one has... literally it is a freaking special order battery which is usually out of stock from my experience. If that battery was some other voltage other than 3V the Sparc power source should be strongly reconsidered.
The Vortex does not blink or dim when the battery is low, but instead is does something extremely weird... it will not turn off. Instead of cycling off after holding the power button for 4 secs it turns off until you let go of the button and then turns on again. Definitely weird as a low power indicator which initially made me think something was wrong with the sight and I even removed it and packed it up to send back to Vortex. After realizing that the unobtainium-like CR2354 was unobtainable, I reached for an industry standard 3V CR2032 available anywhere. The CR2354 is basically the larger diameter, thicker, and longer running version of the CR2032 so just expect the CR2032 to not deliver the same run time.

SOURCES
Vortex Optics - http://www.vortexoptics.com