Introduction: Retrofitting a Nemo 8C Dive Light With a LED Spot

By Christian Liljedahl
About: I am creating interactive installations and performances. Inviting the spectator to participate in various ways I use any media possible to bring "the idea" to life. Electronics, computers, wood, rope, water…

A friend of mine have several old Nemo 8C dive lights. It is a sturdy lamp, favored by many divers around the world.

But as with anything having a classic halogen light bulb inside, the power use is high, and the light output is only great when you have absolutely fresh batteries.

As a test, we have retrofitted the Nemo dive light with a 12 V 7W LED spot.

As you see in the video, the light output is huge, and our tests so far show impressive battery life.

Step 1: Find a 12 V LED Spot and Make Room for It

Find a good quality 12 V LED spot.

I used a 7 W 12 V LED spot of the type to replace halogen light installations from Aura Light.
I would just go with whatever quality brand LED spot you have available locally.

7 W of LED light is roughly equivalent to 50 W of halogen light. That's a lot of light!

The ones with a GU 5.3 socket are great, because the GU 5.3 is basically two straight pins, that are easy to solder wire onto.

  • Bend up the metal strip connectors for the old bulb
  • Using a drill or a clipper, cut away the plastic of the old socket, and make room for the back of the LED
    • Make sure to make the hole deep enough to have the spot fit under the glass of the lamp
    • Take care to still leave the battery shoes intact, since we want to reuse all that.
  • Cut the metal strips from the old bulb away

Step 2: Solder Wires to the LED Spot and Mount It

  • Solder two pieces of wire to the LED spot.
    • The GU5.3 has nice pins that is very easy to solder wires onto.
    • Polarity is no problem - The LED spot will have rectifying diodes inside fixing that.

  • Solder the other end of the wires to the metal strips.
    • If you are having trouble getting the solder to stick, file a little bit on the strips to disturb the surface

  • Mount the LED spot in the hole you made, and make sure it is embedded deep enough to fit behind the front glass.

  • Once you are sure the assembly works, secure the LED spot with some hot glue.

Step 3: Put It Together. Test It!

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.