[Al Skierkiewicz]

Micah,
The zener is not really needed unless you are determined to keep the LEDs at a fixed brilliance. Please remember that the battery voltage on the robot easily gets down into the 6-8 volt range during a match. What Ether showed is four LEDS in a string and several string in parallel with a series resistor to limit the current through the diodes. You could choose a three diode string and recalculate the series resistor. The string would stay on if the voltage falls to the 6 volt range. If you think you are up to it, a current source using a FET or transistor might be a better choice in this application.