Surface or Onboard Battery

Control Boards, Controllers, Tethers, Ect.
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ROVER3D
Posts: 128
Joined: Nov 9th, 2012, 7:45 pm
Location: Wuppertal, Germany

Re: Surface or Onboard Battery

Post by ROVER3D »

Everytime i recommend lipoly for use in ROV people tell me about the caution. So i will you same facts.

You can take Lipoly under high (water) pressure (only in a plasic bag) without loosing function.
You can freeze it under -20°C and you can take strong current without voltage breaks down.
You can easily connect Lipoly pack without problems self drain.

and at least: Think about overload. Lipoly Cells deliver strong current... before your batterys will burn all the other burn... :lol: and "the other" you can protect with fuses 8-) (please protect every circuit with fuses!!!)

Only ONE rule you have to observe:
Never let cell voltage under 3,1 or over 4,2V...the only thing!
(i did and nothing happend too but cells are dead!)
Weight isn't so much a factor in an ROV as a quadcopter drone.
For every weight (1kg) you need (1Liter) buoyancy to compensate. You dont need to carry but you need to get the ROV back out of water...thats the Problem. Try it.
Nice thing: My four old 12V 12A gel-batteries with 9,6KG against my Lipoly Pack (8x4S 5000mA) with only 2,8KG. 7 liters buoyancy not needed!
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bikerbones1968
Posts: 374
Joined: May 10th, 2012, 5:21 pm
Location: Annapolis Valley Nova Scotia
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Re: Surface or Onboard Battery

Post by bikerbones1968 »

leeinmt, I am into FPV myself heading to the North American FPV meet in Montreal this weekend.

Anyway IMO two of the most important things to consider when building an ROV is:

1. Hull integrity. Design, build, test, test and retest BEFORE you load it with electronics and batteries. If you build it correctly and know its limitations you should never have an issue. I know my design will operate all day at a 200 feet depth. It might even make it to 300 feet but my known testing limit is 200 feet so that's where I limit myself.

A simple way to test your design is to first select a target depth that you will typically operate your ROV at. Seal your hull, and throw some weight in it as if it was loaded with your onboard equipment. Now throw some external weight on the exterior and submerge it your desired working depth. Leave it there for an hour, two hours or overnight if you like. Return it to the surface, open and inspect. No leaks, no damage, then you know your design works and have somewhat figured out a safe margin to keep your dives at. Retest, its best you verify you have repeatable results. I personally tested my system about half a dozen times. Anchored to the bottom, with a buoy on the surface and left over night. If you have a failure then you need to redesign and the only thing lost is your time and a little material not a $1000 dollars worth of hardware. Its the KISS approach for pressure testing but it is a proven method.


2. Knowing what's going on inside. Like FPV get an OSD to display data on your screen. Monitor battery voltages, current consumption, internal/external pressures, temperature, compass headings etc... and most importantly a leak detection system. It goes without saying if you get so much as one drop of water inside you want to know about it as soon as possible, so a properly designed leak detection system is a must.

This is my homebrew system and it performs exceptionally well.
http://www.youtube.com/watch?v=moE6Oryyvww
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njs552
Posts: 61
Joined: Jun 10th, 2013, 6:22 pm
Location: Sacramento, CA

Re: Surface or Onboard Battery

Post by njs552 »

Hi,

I have been mostly focused on surface power, but I am interested in onboard LiPo power because they are small and can sustain high current draw, and the tether would not be as heavy.

I have used surface power before at 48v, but I know having 12AWG wires in the tether will not be easy for maneuvering. I plan on having 250ft of tether, and 250ft of 12AWG cable is pretty heavy. The advantage is that the voltage drop will be less than 5v.

The other option is to put a dozen 2200mAh LiPo's in parallel in the ROV, so I get about 26,000mAh, or 2.5-4hrs of runtime. Recharging would take a long time for 12 of these batteries though, and I am usually running for longer than 4hrs. http://hobbyking.com/hobbyking/store/__ ... _Pack.html

Any thoughts?

Thanks,
nj552
DavidF
Posts: 101
Joined: Aug 27th, 2012, 1:15 pm
Location: Delaware

Re: Surface or Onboard Battery

Post by DavidF »

maybe run an a/c generator on the surface, send a/c current down the teather then use an inverter to turn it to d/c??
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ROVER3D
Posts: 128
Joined: Nov 9th, 2012, 7:45 pm
Location: Wuppertal, Germany

Re: Surface or Onboard Battery

Post by ROVER3D »

The other option is to put a dozen 2200mAh LiPo's in parallel in the ROV, so I get about 26,000mAh, or 2.5-4hrs of runtime. Recharging would take a long time for 12 of these batteries though, and I am usually running for longer than 4hrs.
Hi,
why using only 3S and 2200mAh Lipo? 4S 5000mAh?
You can charge the packs very quickly.
Something to know:
1. You can load the complete pack (26Ah) with 1C = 26Ah
2. You need 20% time for 80% load and an for the last 20% need 80% time so if you want to dive again load only 80%
3. Think about 3S weak voltage is 9,6V. If anything need 12V (my pressure sensor needs 12-30V) you have to use 4S!

greetz
njs552
Posts: 61
Joined: Jun 10th, 2013, 6:22 pm
Location: Sacramento, CA

Re: Surface or Onboard Battery

Post by njs552 »

I selected the 2200mAh 3S mostly because my ESC's can only take 2 to 3S. They need at least 7v to operate. Everything else on my ROV is either at 12v, 5v, or 21v. I need at least 9v for everything to work properly. The last consideration was because of price vs capacity.

So I can charge the pack while they are in parallel? Or would each pack need to be individually charged?

Thanks,
njs552
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bikerbones1968
Posts: 374
Joined: May 10th, 2012, 5:21 pm
Location: Annapolis Valley Nova Scotia
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Re: Surface or Onboard Battery

Post by bikerbones1968 »

You can charge Lipo's in parallel. The chargers just sees it as one BIG pack.

https://www.youtube.com/watch?v=WY194Md6KNg
leeinmt
Posts: 27
Joined: Jun 9th, 2013, 4:41 pm

Re: Surface or Onboard Battery

Post by leeinmt »

Almost too many options on batteries, including lithium ferric oxide which is much more stable (and expensive). It's what I use on my Quicksilver ultralight aircraft that I fly out of the farm here (for the Rotax engine electric starter).

I'm going to put the battery decision on hold for now and focus on pressure hull integrity. That could later influence how I power this thing.

I've got my motor enclosures and thrusters pretty much done. So now I need to work through how to safely hydrostatic test a pressure hull that will contain the batteries, esc's, cameras, etc.

This forum is segmented into various aspects of ROV, so I will migrate over to the hull thread to keep from drifting off topic.

Lee
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