Undergarment

[john j]

I can honestly say that the system we have worked out is nice and I don't have any serious problems with it. It's not perfect, but overall I'd say it's one of the more reliable pieces of gear I have. The only drawback is that it is quite expensive.

I initially started with a 50 watt pad on my chest under my drysuit. That cranked out so much heat that it would sometimes burn me. I am not using a thermostat, just on/off control, which is fine for me but I could see that some other people might want a thermostat. The on/off switch is easy to reach and it's simple. Now I have a heated jacket that has heat all around, even in the arms and neck. The heat is not as intense as the pad, but it totally surrounds my upper body and feels really nice. I have gloves and socks that plug into the jacket too, but I find that I only need them in very early spring when the water is at its coldest. Of course, the more stuff I have plugged in, the faster the battery dies. With just the jacket, I get about 2.5 hours of continuous use from my onboard battery which is 13.5 amp-hours. This battery is roughly the size of an OMS 13 ft3 argon bottle without the valve. This year, we have added underwater pluggable connectors so we can have a battery hanging on the deco line or whatever and plug into it if we need to on really long decos. You can also get a larger battery pack from Patco and then you wouldn't need the underwater pluggable connectors, but the high capacity batteries are not cheap. Of course, with the U/W connectors, if my main battery floods, I could plug into another one and still get heat. For the batteries that we hang on the deco line, we can use the cheap sealed lead-acid variety which will save hundreds of dollars.

Of course, I still use really good drysuit underwear and I'm not relying on the electric heat 100% becasue it could fail. In reality though, for me personally it would not be realistic to attempt these really long dives without some kind of active heating device. I get cold very easy compared to most people I dive with.