Assemble the lamp as you always do.

Make sure the hot glue have not interfered with the batteries ability to touch the battery shoes.

TEST TEST TEST

Obviously a dive light is a safety item. You don't want it to burn out on you in the middle of the dark water.

I ran this lamp for 4 hours on the table, to make sure, that it would be stable.

A powerful LED spot like this 7W spot will produce quite a bit of heat. No where near as much as an equivalent halogen bulb would produce, but after the 4 hours the temperature inside where up in the 50-60 degrees Celcius area.

Using the light under water will provide much better cooling.

So, make sure your light works on the table before taking it out to sea. There is a lot of quality difference between LED spots, and if you have chosen a cheap crappy one, there is a good chance, that it will not survive the temperature inside the lamp house.

Battery time

The batteries I used for testing was not new, and had a combined output of 9.2 V when I started the test.

After 4.5 hours the voltage had dropped to 6.9

New batteries would have given out 12 V

Still, after the 4 hours and with only 6.9 V supply I had massive output of light.

Further studies

I have not yet tried out this hack in the water on a dive, but I am quite confident, that it would do the job at least as well as before. The light output will be similar or even more powerful - But the battery life will be much much longer.

I will post an update once this light have seen some sea trials.