Hi All,
My project team is looking to integrate the BlueROV2 to an energy harvester on the waters surface. The current challenge were facing is how to supply the energy that we harvest to the ROV. We are thinking of either having one battery on the energy harvester and then powering the ROV directly through the tether or including a battery on the ROV as well. Either way, the tether will need to provide power transfer. Can this be done with the standard 50m Fathom Tether?
Thanks
As far as I’m aware the standard fathom tether’s cables aren’t intended for power transfer, especially considering the amount of power used by the thrusters. The wires are quite a thin gauge, and the twisted pairs aren’t shielded from each other so there would likely be some issues with electrical noise corrupting the communication signal.
Have a look at the OTPS High Power Tether which tells you the kind of specs you’d likely want.
Thanks for your response Eliot.
Its understandable that the thin gauge of the wires in the original fathom tether may be too small. However, the twisted pairs in the High Power Tether are also unshielded so maybe electrical noise is not an issue? Only difference between the two cables I see is the different wire gauges for power transfer (23AWG vs 26AWG). The high power tether is also significantly more expensive and is a route we prefer to avoid.
I am rather new to the ROV world. Would it be manageable to have two tethers attached to the ROV? One for power supply and the other for communication signals?
Since it’s DC power it’s likely ok for the most part, but if the thrusters get turned on suddenly or whatnot there might be power spikes that could corrupt the occasional communication. If it’s not a huge issue to have a slightly damaged video frame or missing mavlink message from time to time then the lack of shielding is likely ok in your case.
Two tethers is possible but not suggested, because it significantly increases the risk of a snag. It also requires attaching them together at sever points along the length, which makes it harder to wind them up and means you’ll likely end up with extra bits of junk stuck between the two cables.
The OTPS cable is indeed quite expensive, so you might want to look at alternatives from some of the Chinese manufacturers who can make you a custom cable with the actual length and characteristics you want. Alternatively one of the bluerobotics engineers might be able to give you a current specification for the existing Fathom tether. I’ve also just realised that since the fathom has 4 twisted pairs, if you’re only using one or two of them for comms you’d likely be fine if you use one pair for power and one pair for ground, since two 26AWG wires > one 23AWG wire.