Changing batteries in humidity and heat

[DevilEyeDog]

I placed my camera into housing in an air-conditioned room. I will be on a boat for three dives and there is no way my one camera battery will last for all 3 dives. Olympus TG-6 and I usually shoot 200-300 shots in one dive. I find it’s usually dying around 2-2.5 hours so lasting 3-4 hours is not going to happen.

I need to change my battery on the boat in the middle of heat and humidity.

Yes, moisture munchers are in the housing but it’s 80% humidity and 95F in tropical Indonesia.

How do I avoid the fog?

 

[bvanant]

You can change the battery on the boat then blow out the housing with some air from a tank (it is really dry), but to me 300 shots/dive seems like a really really large amounts of photos. How many do you keep at the end of the day? I typically shoot 60 per dive and throw away half, the trouble is that when I am shooting I think "this will be good" but in fact it is mostly not.
Bill
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[rmorgan]

How do I avoid the fog?

If at all possible, leave the camera out of the air con overnight, or even for the hour before the diving starts. Starting out with a cold camera is a sure-fire recipe for condensation. Changing a battery on an housed TG doesn’t take more than a couple of minutes—do the change methodically, but quickly, and drop the rig in the camera bucket if there is one. And, what Bill says—are you really averaging 250 actuations per hour of dive time? That’s a picture every 15 seconds . . .

 

[TostitoBandito]

If your housing supports a vacuum pump, that pretty much eliminates the need to ever worry about fog. Lowering the pressure makes the air inside the housing much thinner and drier, and it won't tend to condense on anything.

 

[bvanant]

Well it lowers the relative humidity (at a constant P) but not really making what air that is in the housing drier and if there is even a tiny drop of water in the housing then all bets are off.
Bill

 

[TostitoBandito]

Yeah it's not gonna help if you have actual droplets already formed, like from dripping something inside while changing lenses. I've done that before and had a droplet fall across the inside of my dome port mid-dive. Not fun.

But it does help if you're just someplace hot and humid where you're worried about things fogging as soon as the housing hits the colder water just from the moist air inside. The standard moisture-muncher use case. I've found that I've never needed them since moving to a housing I could put under vacuum. I usually put my housing around 8-10 psi below ambient, so like 30% of normal atmospheric pressure.

 

[bvanant]

Wow, that seems a lot. Most vacuum systems that I know about turn the light on at about 20-25 kPa or 2.5 or so PSI. I don't think my AOI vacuum pump could pull 10 PSI.

Bill

 

[TNEngineer]

I'm impressed that you get that long on a single TG-6 battery. I've found a single high quality battery safely lasts one ~60 minute dive, but never the full length of a second ~60 minute dive. I keep the screen at low intensity but still, I cannot get two dives.

The battery indicator is not linear... it shows 100% until about the last 10 minutes and then goes red, and finally the camera shuts off. For reliability I just swap in a new battery on every dive. I do this on the dive boat, no special prep other than drying the outside of the dive case. No dessicant in the case and no fog.

 

[TostitoBandito]

Wow, that seems a lot. Most vacuum systems that I know about turn the light on at about 20-25 kPa or 2.5 or so PSI. I don't think my AOI vacuum pump could pull 10 PSI.

Bill

Actually my bad, got the wrong units. My pump is in inches hg, so 10 there is more like 5 psi. I can get it up to 15+ on the pump which is over 7 psi, but my hand gets tired and there's not much point going any further. Still, it's a significant pressure reduction from sea level, equivalent to over 10000 feet of altitude.

 

[bvanant]

On my AOI if I pump too much, then the green indicator goes green/red. I suspect there is a range where the EE guys choose to optimize both vacuum and the ability to monitor temperature changes.
Bill