Underwater or Above water??

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lockdownking
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Underwater or Above water??

Post by lockdownking »

I am building an ROV that willl operate on a 12 volt marine battery. I want to get some input on building my ROV to accept the battery on-board or should I keep it closer to the control panel?
My rov resembles a tank and will not be required to be neutrally buoyant.
The gearing system has plenty of power from the battery to control the weight, so that's not a problem.
The question I have is Does anyone see any issues with enclosing a 12 volt marine battery?
I have thought about gas buildup, but I don't think there will be that much.
The reason for putting it on board would alleviate the worry of voltage drop over 900 feet of power cord.
Your input and thoughts please.
Thank you.
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Billrose
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Re: Underwater or Above water??

Post by Billrose »

Almost any battery will produce some 'gas' Which can cause problems. 1 Fire! 2 Explosion! 3 Compression and then explosion..

In the design build in a valve to bleed-off the gas. (Think of a valve on a hot water radiator )

I used to have to bleed off a battery pack on an Rov. It used a hydraulic pipe fitting to open before removing the bolts to inspect the insides. Before this valve was fitted the person unbolting the lid got hit in the face as the pressure was released and then went on fire from the cigerette he was smoking... Funny, very funny but also very dangerous.

Are you building a bottom roving crawler?? from your description it sounds something like it could be...?

Regards
lockdownking
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Re: Underwater or Above water??

Post by lockdownking »

Thank you Bill Rose,
Yes. It is a bottom crawler. I thought about putting in a manually controlled valve but was trying to figure out how to measure the gasses that would eventually build up inside. I have not started building because I wanted to see how many things could go wrong and how to fix them instead of finding out the hard way. I will be using compressed air on each dive to vent the casing. The design is similar to a paintball gun and will inject air into the case and out the pressure vent.
Another thing I am considering is venting the battery casing and the electronics area to keep condensation from building up and getting everything wet.

I guess I could vent it using a manual button every 15 to 20 minutes.

Something else I would like some input on is the camera casing and keeping condensation from building up in it. Any ideas or can I just put a damprid material in before each launch?
rossrov
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Re: Underwater or Above water??

Post by rossrov »

Hi lockdownking. Metal casting a great technology for ROV work I reckon. Interested to see some work later on :)

Yep, above water power outside the cost/ability/safety range for most of us here. With regards to the battery, how many amp-hours? Have you considered a less potentially explosive (I totally agree with billrose) battery technology than lead-acid? Personally I do not know how the lithium or other technologies are from a safety point of view, though some others here will have no doubt checked this out. If using lead-acid, consider making the battery housing seperate from any other electricals, and have the least air (gas!) space possible in the housing. Unless near the surface, deliberate venting/purging will have the outside pressure to contend with.

Ross
lockdownking
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Re: Underwater or Above water??

Post by lockdownking »

Thanks rossrov,
I have taken the outside pressure into consideration and have thought about operating the battery casing by itself, separate from the rest of the electronics under pressure to begin with. The only reason I am going to use lead-acid is due to the availability of them at the local Wal-Mart. Plus they have warranty's. I have not figured the amp per hour yet.
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Billrose
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Re: Underwater or Above water??

Post by Billrose »

My speciality was sea-bed tracked machines. Cables, pipes, mining, dredging & salvage.

Any help I can offer. Feel free to ask any and all questions. (Especially the ones you would not ask your mother..Ha ha!)
Just having a laugh...
No really got lots of practical and theoritical (cant spaell) advice

Regards

BEER! Thats good advice
lockdownking
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Re: Underwater or Above water??

Post by lockdownking »

Billrose,
Thank you for your input. It will be very useful for me especially with money being tight. You might see something during the build that I don't.
I am going to put the build on you tube in stages and hopefully it will move quickly.
Right now I am in the process of getting two window control motors from a car to operate the turning of the cogwheels on the tracks. Once I get these, I can start figuring the size of the main box that will be mounted to the crawler. I am planning on using a detachable box that Wal Mart sells which is made of plastic. It will mount above the main box.
Capture.GIF
Capture.GIF (86.73 KiB) Viewed 4378 times
The two cog wheels on the bottom will be spread further out to the front and back for stability purposes instead of directly under the vehicle.
The light is mounted on the outside of the cam tube.
There are 4 motors not just two, the other two can't be seen because they are on the other side but they are connected to the same power supply.
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Billrose
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Re: Underwater or Above water??

Post by Billrose »

Your Rov looks ok and your basic idea is ok to.

So can I ask... How deep do you think you can go with this (feet, metres...miles..!) Just asking because the depth can alter my advice.

In theory a tracked rov can go all the way to the bottom of the ocean. I have had them down around 1100 metres.(3600 feet)

Regards
lockdownking
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Re: Underwater or Above water??

Post by lockdownking »

I didn't plan for it to go very deep for what I need it for. But I guess that because I am casting the housing myself and can control the thickness of the hull, I can pressurize the gear box with compressed air up to 3,000 psi. I could put the battery on the topside with me with the control board and go to a depth that would have an outside pressure of 3,000 psi plus whatever the thickness of the hull can take. I have not researched the strength of aluminum for this use.
Using pressurized air will not impede any operations of the mechanical or electrical systems. However, when it comes time to put hydraulics in, it could prove to be a challenge.

So, to answer your original question, I only plan on going about 300 to 500 feet deep at the most using only slightly pressurized air.
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Billrose
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Re: Underwater or Above water??

Post by Billrose »

Ummm! compressed air will add positive lift... <><

Unless the volume of the air is quite small :idea:

Most seabed machines used oil to fill open voids. (Any oil or non-conductive liquid.)

Regards
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