I have done plenty of research into the HID light and here is what I have found. HID lights are very susceptible to heat, even stated on the Welch Allyn website. The ballast must not reach 90 deg. C. Therefore, the ballast, unlike a halogen where the lamp heats up, must be cooled. To do this the light head has to have a tight tolerance to the ballast, slip fit would be nice. Also remember that if the ballast is more than 6 inches away from the power source, battery, the wires must be twisted to prevent voltage spikes which will kill the ballast and the lamp.
The fittings must be waterfight fittings, obviously. JB weld is not and will never be a watertight seal. JB Weld is for replacing metal for cosmetic use only, basically.
I have designed a light head which does take all of this into account and it works just fine. I am in the process of getting WA lamps, 10W, !2v, HID lamps delivered in a 5 pack and will be making canister lights. System has already been pressure tested and I will let you know of the thermal characteristics when I get the thermal tests results back.
How do I know all this stuff you might ask, I am an Electro-Mechanical Engineer that loves (and teaches) diving. This is what I do for a living and I just thought I would make a canister light myself. Is all you need is a compentent machine shop to do the rest. When making these underwater lights, make sure the o-ring seal is correctly done. I have seen to many underwater lights leak because of incorrect o-ring seal. For me to tell you how is a long drawn out process but I will come up with something to help everyone. If you have any question please feel free to email me.
