Hi guys. I had a favorite non-dive light that went diving with me, unintentionally. When I realized what I had done, I freaked for a second, then relaxed because it was freshwater and everyone knows that feeshwater won’t conduct low vo DC, right? Well… the light itself worked just fine in the water but after I got out, the LEDs remained dimly ON. So I took it all apart, blew it out and left it in the sun to warm. The next day I noticed little green corrosion trails between my switch contacts (on a piece of PC board). Also the lithium batteries were black and nasty.
I remember from by telephone tech days, a PBX (which ran on 48VDC) got thoroughly doused by a fire sprinkler head. The bare copper wires immediately grew a blue green fuzz, three to four INCHES long, all inside the cabinet! It was, of course, a type of electrolysis, similar to what I was seeing on a much smaller scale.
So, I concluded that, indeed, there was enough conductive impurities or whatever in the water to conduct 6V 20mA. I replaced the batteries and proceeded to waterproof the light by injecting VersaChem dielectric silicone (in a syringe) into the On-Off switch (until it oozed out), all over the bare solder contacts and short wire spans, as well as coating the batteries too.
Since then I have tried to damage the light by immersion and she seems to hold up like a trooper. I even left it on in the bottom of my aquarium for a day with no harm done, not even to the fish who found it curious.
So, I thought I’d pass it along. It would seem that you can further ensure your dive light to be fail safe by applying dielectric grease to its batteries and innards. Yes, it is a bit messy but after you wipe up, the silicone stays inside and the light is nice and dry to handle.