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High altitude, cold water operation?

For the third year in a row we will be attempting to locate a WW2 era plane that went down over the Sierra Nevada mountains about 70 years ago. It is believed to be in a lake at about 11,000ft. Two years ago fires cancelled the trip and last year it was record snow fall, fingers crossed for this year. I was not planning on taking my bluerov last year but now I’m thinking its the better option. My questions are… what sort of battery life can I expect in water that is just above freezing using the Blue Robotics battery on low in calm water with six bluerov lights?Anything else i should be aware of operating at that altitude? Anyone ever strap one of these to a pack horse?(not really expecting an as answer on that one but why not ask)

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Hello @BoatSD,

If there water is calm I expect the battery to perform just fine on lower gains. I would just vent the enclosures to make sure there is no positive pressure in them.

@kklemens an @adam please correct me if I’m wrong.

And no, I never thought of strapping one to a pack horse…

Sounds awesome! Would you need to recalibrate/scale the pressure sensor? Not sure how ArduSub handles these situations, maybe it automatically adjusts for ambient baro? If not, it’s unlikely you will get accurate pressure readings at 11,000 ft, as pressure (depth) will be less than actual position in the water column. Maybe this isn’t important, but possibly is if you need accurate positioning. Even if you rezero the sensor lakeside, I don’t think you’ll get a 1:1 change on displayed depth to actual depth.

As @williangalvani suggests, make sure the enclosure is vented. I would also run the system for a few minutes prior to the dive to heat the internal air, then vent the system, then there won’t be such as large pressure differential as the dive progresses (if you start with cold air, that air will heat up, causing increased pressure and probably a lot of condensation)

Good luck!

Correct depth isn’t all that important for this one. I would be curious to see just how deep the lake is but guesstimating will be fine. Ill mess with it if i have time.

I figured i would leave the vent plugs out for the haul up. I bet condensation will be problem, good call. Ill be sure to warm up the enclosures and bring plenty of moisture packs, maybe even some vinegar. Would suck to go all that way and not be able to see anything.

I’ve got some experience using BlueROV2s in near-freezing water. My recollection is that the battery life is not dramatically decreased, but there was a noticeable difference. It’s so dependent on what you’re doing though (lights, thrusters) that it’s tough to compare one dive to another. Definitely doesn’t hurt to keep the pack warm or pre-warm in low air temps.

I haven’t ever strapped one to a pack horse, but I have backpacked with one in a group. We wrapped it in two pieces of closed-cell foam and tied it with string. We then strapped it to hunting frame pack, something like this. We used the thin tether on a lightweight extension cord reel, with a cheap underwater connector on the ROV end to allow packing the tether separately.

Regarding the pressure, you should be fine if you calibrate before the dive, what we are actually measuring is the (pressure created by the) height o the water column on top of the ROV, which depends on the gravity and water density alone, the atmospheric pressure is an offset we calibrate out.

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We have used our heavy BlueROV2 in near freezing waters in Svalbard. Performance was not really impacted and battery life was barely affected.
I’d take heed of the advice regarding venting, we did the same.