The same is true if you simply run it DC using half the power. The human eye isn't very sensitive to double/half the light power, particularly if there isn't something nearby to compare it to.One trick to help out - persistence of vision. Pulse the LEDs at a bit over their rated DC current, but cut the duty cycle to less than half. Power used goes down to about half, yet the eye perceives almost no change in brightness. You will have to investigate the best combination of operating voltage/current and duty cycle for the LEDs and battery you have.
Well, not quite. LED forward voltage varies significantly with color, shorter wavelengths tend to take higher voltage. Red might be near 1.3V, while blue is near 3.1V. (White is just blue with a phosphor on top.) And that voltage is temperature and current dependent, so things move around under use. One should think of LEDs as CURRENT controlled devices that happen to drop some voltage, not the other way around. That means paralleled LEDs need to be the same color, reasonably matched, and thermally coupled or they won't share nicely. A proper drive circuit regulates the current, irrespective of the voltage. Having the LEDs in series forces the same current through multiple LEDs. The RGB strips I have seen use 3 LEDs in series, so 12V is the nearest standard voltage that allows for simple, cheap use of resistors as current "regulators". 12V LED strips do waste some power in the dropping resistors, but those resistors set the proper LED operating current given a 12V supply. Reduce the voltage and blue LEDs drop out before the others. Raise the voltage too much and the blue LEDs see too much current while the red ones only get a small increase. For 12V LED strips stick with 12V drive, and use a pulse width drive scheme to cut back on the power a bit AND get the benefit of persistence of vision.Every LED I've ever seen operated on less than 3 volts, most less than 2 volts. The "12V" LEDs I have seen were just regular 2 volt ones with an integrated drop resistor.
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by Aaron Carman
by Jake Hertz