Short range wire based energy supply


#1

I am investigating the use of an OpenROV for short range operation in gardened lakes. The operational range would be less then 25 meters. For this application I am thinking about a wired energy supply to get rid of the batteries and the charge process (and maybe replace them with a technical equipment!).

What specification do i need to meet here? My first approach would be to solder the two wires from the tubes to a two wire connection to an ordinary power supply unit, that matches the batteries voltage output and is able to supply enough Current. Anything else? Any advice for a cable/wire?

Thanks a lot for your help!


#2

Here is the update on this from my point: I will use an ordinary power supply unit that has a variable voltage (sample power supply (german)). It can supply up to 20 A.

The batteries have a discharge current of 10 A max, but i feel this is for the extreme scenario that one battery tube failed and one tube has to power the whole ROV with thrusters.

With practical test I would determine the needed voltage at the power supply unit so that after cable losses the ROV has a current of around 9,6 V (3 batteries with 3,2 V) available. For a cable i would assume that every water proof cable would be fine. Anything I missed?


#3

Another issue: What exactly is purpose of the fuse that is in the epoxy in the battery tubes?


#4

Hi:

Here are some points and suggestions:

  • The ROV requires more power than you think when the motors are running at full power. Each running motor can draw something like 7A at 9.6V. The reason the batteries last as long as they do is that one rarely, if ever, uses full power on the motors.

  • The polyfuse that is embedded in each battery pack is designed to protect the battery cells from a continued over-current situation, and to protect the controller board itself from an overcurrent situation that would damage the board- say, what might happen if two of the wires for one motor get shorted together. The polyfuse used will trip at between 6A and 8A depending upon the duration of the overcurrent situation. If you put the ROV in the test tank it is actually possible to trip the polyfuses just by running all three motors at full speed continuously. This is not really an issue during operations.

    The beauty of a polyfuse is, of course, that it automatically resets once it cools down. So no fuse replacement is necessary.

  • You’re probably going to find that you need a power converter inside the ROV to stabilize the voltage being delivered to the controller board. Unless you use thick wire, the voltage at the end of the tether will swing wildly as the power draw of the ROV changes (with use of motors and such).

Hope this helps. Keep us posted on what kind of results you achieve.

-W