I am looking to build/produce an underwater light using approx 4 small bulbs the size of flashlight bulbs or smaller that produce alot of light I want to use green LED bulbs. This is going to run off of a marine deep cycle battery so the less energy these bulbs pull the better. I am going to try to mount them in a waterproof casing. Can you give me an idea of what bulb to use?
A variety of LED bulbs may suit your application. A through hole LED package may be easier to work with if you plan to assemble the LED product yourself. However, modern surface mount LEDs generally offer increased luminous output and efficiency. The Luxeon Rebel is one of the newer LEDs available today. For this LED's package dimensions, it can produce an extremely high luminous output. You can select a drive current for the LEDs which will dictate energy consumption. Lower drive currents will obviously consume less power, but the LEDs will also appear dimmer. On the other hand, a higher drive current to produce more light, but will also consume more power. As a general will LEDs are more energy efficient at lower drive currents. You may want to use a typical drive current as specified in LED data sheets. The LED manufacturer selects this current because it is a fair compromise between energy efficiency and luminous output. When constructing your LED circuitry you must consider the requirement for a constant current source. It is not uncommon for many hobbyists to incorporate a current limiting resistor into their LED circuits. However, this tactic will not work very well within a circuit consisting of high power LEDs, such as the Luxeon rebel. High power LEDs circuits should always incorporate be constant current source rather than a current limiting resistor. If your application permits I would highly recommend using a total of three LEDs rather than four. Due to the LED forward voltage drops of green LEDs, a series circuit of three LEDs may provide a better match to your source voltage. If four LEDs is a definite requirement in your application, then you might want to consider constructing to series parallel circuits. Each series circuit would contain two green LEDs and your current limiting chip.