Battery candles, also known as LED or flameless candles, flicker due to the use of a built-in LED light source. This LED light is programmed to produce a flickering effect that mimics the natural movement of a real flame. The flickering is not due to any instability in the power source or the LED light itself, but rather it's a deliberate feature designed to create the illusion of a real candle. The LED light rapidly turns on and off at varying intervals, creating the flickering effect. This is all managed by an internal electronic circuit within the candle, which controls the LED light’s behavior. The flicker is designed to be random, much like the flicker of a real candle, which can be influenced by air currents and the candle's own fuel source.