[sid]

LEDs drop anywhere between 1.4 Vdc to 4.5 Vdc per LED, depending upon the color and construction. Most red LEDs drop about 1.5 Vdc, though I don't know if this is still true for the super bright ones. So multiple LEDs are often wired in series and share the same current, which saves considerable power. The sum of the voltage drops of all the LEDs in series must be less than the source power, which is about 12 Vdc for most all automobiles, with the difference between the drop across the LEDs and the source power being dropped by a resistor or a regulator circuit.