You could try shoving it into a pipe, so its torpedo shaped, obvious balancing will be a issue.

That or using a wire to power the rov. Obviously this is a idea, not a good one but hay its a idea. What if you stepped up the 12v from the battery to 220v . Sent it down the wire and you can get modules that will turn it back into 12@1A and 5v@1A.

1a isnt great but its not a actual torpedoe.

 

Years ago I did quite a bit of vacuum and high pressure vessel work. I did some buying from a company called Pave Technologies for bulkhead (through the bulkhead) fittings. I am sure there are plenty of other companies making, including custom making, of such fittings and connectors. Some of this stuff can get pricey depending on exactly what you want or need. They will quote you anything you want, you just call out the specifications. That includes vacuum down to a few milli Torr and pressures to about 3,000 PSIG.

When it comes to the water proof / watertight and other terms as well as specifications like NEMA 4X, IP66, DIN 40050 make sure you understand what you are reading because there is a difference between watertight at a depth of 100 ~ 200 feet and splash proof. You start looking at die cast aluminum and stainless steel enclosures. One popular trick is pressurize your container with dry pumped nitrogen. Matter of fact pressurizing a vessel to 45 PSIG is not very much and even with slight sorbtion a good container should maintain pressure. Dry pumped nitrogen is cheap.

I never tried it at any depth but sitting here looking at some GI ammo cans. They are steel so subject to rust but with a good paint finish may work. I am talking about USGI type cans and not the Chinese knock off stuff. A small .30 Cal can easily holds a 12 V 8 AH SLA battery and a 50 Cal can has plenty of room. I believe at one point in your other thread this thing will be submerged for a year? With a good paint finish an ammo can may suffice with some reinforcing.

So now you have more to think about.

Ron

 

Years ago I did quite a bit of vacuum and high pressure vessel work. I did some buying from a company called Pave Technologies for bulkhead (through the bulkhead) fittings. I am sure there are plenty of other companies making, including custom making, of such fittings and connectors. Some of this stuff can get pricey depending on exactly what you want or need. They will quote you anything you want, you just call out the specifications. That includes vacuum down to a few milli Torr and pressures to about 3,000 PSIG.

When it comes to the water proof / watertight and other terms as well as specifications like NEMA 4X, IP66, DIN 40050 make sure you understand what you are reading because there is a difference between watertight at a depth of 100 ~ 200 feet and splash proof. You start looking at die cast aluminum and stainless steel enclosures. One popular trick is pressurize your container with dry pumped nitrogen. Matter of fact pressurizing a vessel to 45 PSIG is not very much and even with slight sorbtion a good container should maintain pressure. Dry pumped nitrogen is cheap.

I never tried it at any depth but sitting here looking at some GI ammo cans. They are steel so subject to rust but with a good paint finish may work. I am talking about USGI type cans and not the Chinese knock off stuff. A small .30 Cal can easily holds a 12 V 8 AH SLA battery and a 50 Cal can has plenty of room. I believe at one point in your other thread this thing will be submerged for a year? With a good paint finish an ammo can may suffice with some reinforcing.

So now you have more to think about.

Ron

Thanks for the info. It will only be submerged for half hour to an hour depending on how much run time I get on the battery, and up to 100ft or so for only that duration. After that, I pull it out of the water, take it home, charge the battery and deploy it again when im out in the boat and wanting to do some exploring.

 

Are you referring to something like this?

No, I was referring to a watertight connector, not a feedthrough.

 

I think the one mentioned in post #10 is the one you need.

 

Thanks for the info. It will only be submerged for half hour to an hour depending on how much run time I get on the battery, and up to 100ft or so for only that duration. After that, I pull it out of the water, take it home, charge the battery and deploy it again when im out in the boat and wanting to do some exploring.

That's nothing. Try an Ammo can from any surplus outlet. That will make for an inexpensive start.

Ron

 

At this pressure and depth, a one square foot lid would have 4,363 pounds of pressure on it. That's more than my car weights. So if you can drive your car over it then you are OK. "The average new car weighed 3,221 pounds in 1987 but 4,009 pounds in 2010 (fromhttps://slate.com/business/2011/06/american-cars-are-getting-heavier-and-heavier-is-that-dangerous.html )"

But if you drive over the case, your only applying 25% of the weight (there are four tires). So that would only apply 1002.25 pounds of pressure.

 

That's nothing. Try an Ammo can from any surplus outlet. That will make for an inexpensive start.

Ron

Will an Army can provide waterproofness for my battery? Or would I need to pot it? I feel like I keep asking the same thing, as waterproofing the battery is the goal, otherwise, I would just submerge it and not care so much, but a lot of you guys recommended I put it in an enclosure and waterproof it etc. Thanks.

 

I think the one mentioned in post #10 is the one you need.

Yeah, it would probably work flawlessly; however, since I have to request a quote for the price I'm assuming it will be ridiculously priced for a hobby-grade ROV and not a heavy-duty industrial grade ROV. I sent the quote request so we shall see. Thanks.

 

You could try shoving it into a pipe, so its torpedo shaped, obvious balancing will be a issue.

That or using a wire to power the rov. Obviously this is a idea, not a good one but hay its a idea. What if you stepped up the 12v from the battery to 220v . Sent it down the wire and you can get modules that will turn it back into 12@1A and 5v@1A.

1a isnt great but its not a actual torpedoe.

I thought of this after the fact. My ROV design consists of 3 PVC pipes oriented in a triangle orientation with a 1/2 PVC frame around it. I attached the design below. Also, I have a trapped door in the center to allow the 12v battery to easily come out for charging and go back in. But after consulting the original question of whether or not this would be safe exposing the battery in water, I'm back at the drawing board in terms of solving this issue without completely rebuilding. The center electronics pipe is 4-inch in diameter, and the outer two pipes are 3-inch diameter. The battery is just barely shy of being able to slide into the 4- inch pipe, but not quite big enough to allow it to do so.

 

The battery is just barely shy of being able to slide into the 4- inch pipe, but not quite big enough to allow it to do so.

Could you use two smaller batteries in parallel?

 

Could you use two smaller batteries in parallel?

I've thought of that. I think at this point going this route would probably be a simpler approach, and if need be I could put one battery in the left far tube and the other in the far right for weight balance and then link them together in the center electronics tube. As the "pipes" coming from center pipe to outer pipes offer both stability and a hole to run wires. Thank!

 

And with the 100, 125ft, that is max, meaning length of tether; however, would likely not use the whole 100-125ft tether capability as not many lakes near me are that depth. But in the case I want to then I can.

Even if you believe you are safe; I would multiply by 3 for design safety.

And... reconsider lithium polymer instead; no critical case, siliconed terminals. They are sealed with no voids.

 

I like the PVC idea. You can test the concept without the battery, sending it down for an hour to see if any water gets in. You could also test through-hole connections this way. The screw-on caps may be suitable so you can have access to the battery or if it is cheaper to just seal the battery and re-charge the battery via the through-hole terminals.

Nominal Pipe Size

O.D.

Average I.D.

Min. Wall

Nominal wt./ft.

Maximum W.P PSI

5"

5.563

5.016

.258

2.874

190

 

Will an Army can provide waterproofness for my battery? Or would I need to pot it? I feel like I keep asking the same thing, as waterproofing the battery is the goal, otherwise, I would just submerge it and not care so much, but a lot of you guys recommended I put it in an enclosure and waterproof it etc. Thanks.

Ammo cans have a rubber gasket on their lids and close with a snap type action. This is a USGI 30 Caliber ammo can. I can easily put two 12 volt 8 AH SLA batteries in it with room to spare. Ammo cans are tough and GI cans are well made. While I never tried it they should easily handle a depth of 100 feet plus. So invest a few bucks in a can and drop it down 100 feet and see if it leaks. This is not rocket science, this is a 50 Cal ammo can. A 50 cal can is Military "M2A1" Ammo Can 50 Caliber New 11" x 5-1/2" x 7" Olive Drab. A 30 cal Ammo can is approximately 11 inches long x 3½ inches wide x 7½ inches high and weighs about 4 pounds, 8 ounces when empty. I buy them in bulk normally with 30 cal cans inside the 50 cal cans. Like I mentioned earlier look for US GI Surplus cans, do not buy the cheap Chinese knock off cans at Walmart or similar.

Ron