Does anyone know how much battery power (in volts per hour perhaps) that the BlueROV2 uses when it has the battery installed but isn’t connected to a laptop / using thrusters and lights? I’m considering changing the way we do things for our inspection work so that we install the battery at our workshop before we head out to do an inspection, but I want to be sure that say during a 1.5 hour drive to the inspection site that we aren’t going to lose too much battery power and need to change the battery part way through the inspection?
The laptop (or surface computer) when it’s connected to the ROV via a tether interface, will not draw any power from the ROV.
When your surface computer is connected:
The computer side tether interface will start to draw power of your computer via the USB cable (around 500mA / 2.5W).
The ROV video stream will connect to your QGroundControl to stream video, and this will make the companion computer to draw more power, but this is insignificant compared to the motors .
Internal temp could be an issue if powered on for that long. Taking the vent plug out could help a little but it is best to immerse the rov in water to dissipate the heat… Electronics don’t play well with high heat. Not sure its worth it as it only takes a couple of minutes to put battery in.
I am in agreement with Kaos as to the internal temperature of the Control Electronics WTC being a critical driver when the ROV is not submerged in cool water.
During bench top testing in my home I found that the internal temperature of the Control Electronics reached 54 deg C while the temperature outside of the Control Electronics WTC was a cooler 27 deg C with only 1/2 hour or less of on time.
Therefore running for 1.5 hours before being immersed in cool water will probably result in unwanted excessive thermal stressing of the Control Electronics over time.
Thanks for the replies everyone. I must admit that I hadn’t thought about the internal temperature issue. It might be OK here in winter where it is struggling to get above 12 deg C right now, but summers here are brutal with 40+ deg C pretty common.
@TinyDiver, I can also second that you might stumble into problems with internal temperature.
It’s something we battle with constantly down here in Aus.
Our best solution to deal with temp (and could also work for you), was to install a battery cut off switch on the ROV - check some of my other posts. This ensured that the vehicle didn’t overheat when it was out of the water.
In my experience, and idle BROV2 draws about 8 to 10 watts (assuming you have latest R3 ESCs. Can be significantly more with older versions.) The standard battery is a bit over 250 watt hours, so that predicts about a 25hr idle life. I’ve accidentally left an BROV2 connected overnight on the bench, and it was fine. Running the motors dramatically shortens this - so depending on the loads on a typical dive for you, the impact is likely minimal. You may consider adding a solenoid or FET driven by a BR switch to your battery compartment - an easy modification that makes usage much more convenient! I’d recommend something rated for at least 100A.
I’ve also done some extensive testing of thermal stress on the internals of an BROV2. Placed sealed in SoCal sunshine, in a parking lot, internal temperatures reach a steady state at around 70 to 75C. The only performance effect measurable at the time were issues with video lag, likely due to the encoding taking place on-board the USB camera being slowed by thermal throttling. With both ESCs and general electronics, I wouldn’t start to be concerned until measured temperatures approach 80C (@ chip level.)
In warm waters, internal steady state temperatures reach about 55C, with water temperatures from 21 to 26C.