I’d like to introduce our Cobalt Series waterproof connectors to the BR community. Click on the link for pricing and options. We’ve been producing these for about five months now and they have generated tremendous interest and a lot of satisfied users.
Highlights:
600 meter depth rating
M10 X 1.5 thread (fits Blue Robotics enclosures)
316 stainless steel connector shells
3, 4, and 6-pin versions available, with 8-pin versions soon to come
Although your connectors are mentioned briefly within a few other discussions within the forum, I cannot believe this discussion has not got more replies since this release of connectors appears to be some kind of revolution with some unique balance between price and performance.
Since I am ignorant in electricity, could you please explain how the female connector rating (20 amps for the thruster cable termination kit) and the male bulkhead connector rating for 3 pins (12 amps) are compatible with the T200 ratings itself (24amps nominal and 32amps maximum).
I agree, these connectors are some kind of revolution! But perhaps I’m biased…
The current ratings get a little complicated, but here goes:
The contacts used in the 3-pin connectors are rated by the manufacturer at 11.2 amps assuming a 10-degree C temperature rise in air. This means that if you pass 11.2 amps through the contacts while they are dangling in mid-air, their temperature will go up by 10 degrees C. The contacts themselves, being made of metal, can of course handle much more heat than that. But the manufacturer knows that in many cases the contacts will be housed in plastic, which can be quite heat-sensitive. So the manufacturer states a very conservative 11.2 amp rating.
In the case of Cobalt connectors, the contacts are housed in PEEK plastic. The glass transition temperature of PEEK is 140 C, compared to about 60 C for nylon. So the PEEK is MUCH more heat-resistant. That’s why I bump the rating up a little to 12 amps. Perhaps I should bump it up a lot more, but I’m being conservative at this point.
Now regarding the thruster… The thruster has three wires. The ESC splits the current coming from the two supply (battery) wires into the three thruster wires. So each of the three thruster wires actually only sees about 2/3 of the current of the supply wires. An electrical engineer might argue about the specifics of that, but that is roughly what happens. So if the 3-pin connector is rated at 12 amps per pin, that is essentially the same as an 18-amp rating (18 * 2/3 = 12) for a thruster or similar application. However, I have done dedicated testing of the T200 thruster hooked up to a 3-pin Cobalt connector. I have run it at 24 amps through the supply wires long enough for the temperatures to stabilize (at least 10 minutes), with no visible degradation on the connector contacts. To be conservative, I thus give the 3-pin Cobalt connector a rating of 20 amps when used with a thruster.
The T200 can draw more than 20 amps, though, as you pointed out. That’s why I try to be very clear about the current rating of my connectors. So far I have not had any customers report damaged connectors due to high currents, possibly because they’re only experiencing higher currents for short bursts.
I would add something to this and say these manufacture ratings were also hanging in free air. As soon as you put these into service on an ROV, and especially in one being used in moving currents, the water is going to take out a LOT of heat.
Hi Damon,
Really interested in your products. I really want to set up a detachable connector for the tether on our BROV2. Would your connectors work for that?
Cheers
Ben
Thanks for getting back to me Damon. I actually already had a look at your cable termination kit and the process looks rather tricky! I was thinking of using your BR specific M10 bulkhead with your single ended cable and joining the latter to the tether using this method: Tether Quick Disconnect - #87 by Ben595. What do you think?
Ben, yes, the method of splicing one of our single-ended cables to the tether would also work well, and doesn’t require soldering in tight spaces. With either method, the key to success is roughing up the surfaces of the parts to be potted using sandpaper and making sure they are clean before potting.
Ben
Like a lot of people that get a BR2, i discovered i wanted a disconnect on the tether, to aid in portability. I have used the Cobalt Termination Kit on both of my tethers, I have the 8 conductor Tether and the slim 2 conductor tether. I used the 2 part Loctite Marine epoxy for Potting. If you get the 8 Conductor tether and want to use the 8 pin termination kit, But beware soldering the 8 pins is tricky, Real tight quarters for soldering. i ended up just using 2 of the 8 pins as i found out i did not need the full 8 pins anyway… When i went to the Slim 2 conductor tether, i used Cobalts 3 pin termination kit, it was a lot easier to solder. I have made repeated dives to over 200 ft with no problems at all. Going right to the Bulk head with the disconnect is a much Neater job in my opinion. I am really happy with the Cobalt Termination Kits. Blue trail recomennds a 3M epoxy for potting on their web page, I would have used that, but it is not available where i live. Just make sure you roughen the Tether up with sand paper or emery cloth and clean with alcohol before potting.
As with any tether do not pull directly on the Disconnect , dead end the bight of the tether to the frame of the ROV. so as not to put strain on the Disconnect.
Bought Blue Trail Engineering connector, 3 pin for the tether on my drop camera (will be someday BlueRov2). I wanted to test those connectors for my project as they fit BlueRov perfectly. I used West Systems G/flex 650 two part epoxy for the cable and the connector. It´s difficult to get some of the epoxy´s here, but this one was available and hopefully it will work well. Sea test has yet to be done.
