On-Board Batteries

[niall.nf]

Hi Guys,

Just wondering your opinions on having on-board batteries to power the Thrusters (and possible camera) and running cat5 for signal control?

What are the pros/cons to this setup versus running power along the tether? I know greater depths can be achieved by using on-board batteries. (I'm looking to achieve 400 foot depths)

Im fairly new at all this but from reading the forums and my own research I cant see any benefit to running power over the tether.

Has anyone experience with on-board batteries?


Thanks

Niall

[sthone]

The only down side of onboard batteries that I know of are added weight/large hulls and limited dive times. Other than that I think they are a great idea.

-Steve

[bikerbones1968]

Properly used and properly maintained Lipo's are an excellent choice for on board batteries. I use 3S 5000mah 11.1 volt Lipo's. A bank of 4 packs. They are light weight and do not off gas hydrogen. I am unsure of maximum run time but I have done a little math on this and I am confident of at least 1 to 1.5 hour runtime. Assuming not everything runs constantly.

[niall.nf]

Thanks for the feedback guys.

I have read a couple of places that Lipos can be fairly unstable especially under pressure??.

I'm fairly sure now I'm going to go with on board power. I beginning to lean toward SLA's and have sourced a 12v 24amp-hours battery.


I have 4 1100GPH bilge pumps as thrusters so far, I wont be deploying a manipulator or anything, just a camera.

Do you guys think this is enough juice??

[bikerbones1968]

I have all 4 lipos in my main hull. So I am not worried about pressure on them. I have seen on a blog or post somewhere that some lithium cells are designed and ok under pressure. I will have to look for that post.

[derelicte]

unless you have a breach in your hull, then lipos in a sealed hub aren't under pressure. now if the hull leaks, then you have bigger issues than worrying about the lipos...

[bikerbones1968]

I couldn't agree more with derelicte. With a well-designed and structurally sound ROV, Lipo’s onboard should not be a concern. I just finished testing my design to 250 feet without any hardware onboard. Just a leak detector circuit and sensor board inside. I used weights tied externally to the ROV to descend to that depth tethered via parachute cord and a buoy on the surface to keep sight of it. I left it submerged for over an hour on all three tests dives. When I retrieved the ROV each time I opened the aft closure to inspect for water migration. No leaks so no worries.

[niall.nf]

So are there significant advantages to Lipos compared to SLA??

[bikerbones1968]

Small compact size. Light weight. And can deliver lots of needed current for thrusters and lights. Its critical that Lipos never become over discharged so I am using a lipo monitor on each pack to send an alarm signal to the surface when they become discharged. Also the ESC speed controllers I use are programable so they shut down power to the motor before they reach critical low voltages.

[KR2_Diving]

I am using a lipo monitor on each pack to send an alarm signal to the surface when they become discharged.

Just out of curiosity, what monitors are you using to achieve this?

Cheers,

Ryan "KR2_Diving"