Thought some might like this formula for limiting current when using LED's in your EV. I'm working on replacing my headlights and all other bulbs in the car to LED's. This formua was provided by a friend from OpTek:

The equation to determine the current limiting resistor is:

(OperatingVoltage - ForwardVoltage) / Current = ResistorValue

Example:
(13.5 - 9.1) / 0.5 = 8.8
13.5 volts was used as the Supply Voltage,
9.1 Volts was used as the Forward Voltage, of the LED module I'm using,
0.5 was used as the LED operating current,
8.8 Ohms was the resulting value of the current limiting resistor.

Power disipation in resistors:

VoltageDropAcrossResistor * CurrentThroughResistor =
PowerDissipatedByResistor

Example:
9.1 (Volts) * 0.5 (Amps) = 4.55 (Watts)