Hello, I have always read that when we are operating with the Blue Boat, we should make sure that the batteries do not drop below 12V.
The thing is that when it is running and we are pushing the motors hard, the voltage always drops a bit more than what it shows at rest, almost 1 V less. So, what value is it referring to when it says not to drop below 12V, at rest or while running?
Thank you.
Hi @Pulsar79
At 12v, the 4s battery used in the Blue Boat has individual cell voltages of 3v. While the voltage can go lower than this, doing so risks damaging the cells capacity. So generally, avoid going below that voltage- even under load. When this starts to happen, you can think of it as the low fuel light in your car coming on - you can still drive, but better to think about ending the drive and refueling soon!
Thank you very much, Toni.
Okay, then, if while driving I see that it is dropping below 12 V, it’s better to turn around and reach the shore.
Have a good day!
Note that there’s a battery failsafe which you should be able to set up to warn you about low or critical voltage levels, either from the BlueOS Vehicle Setup failsafes tab, or directly from the autopilot parameters.
Thank you Eliot.
And now, it doesn’t have to do with the voltage limitation, but rather with how to reduce consumption.
We are doing bathymetries with the Blue Boat, some lasting 2 hours, for which we bring 4 batteries of 18000 mAh.
Do you see if the consumption is normal? Is there any way to lower consumption a bit?
The speed is set at 1 m/s; I don’t know if it can be increased and maybe the consumption doesn’t go up as much as the duration decreases.
What do you think?
Hi @Pulsar79 -
I’m surprised you’re using up 4 batteries in just 2 hours, at 1m/s - are you operating in strong currents or rough seas? What other payloads are installed on the vehicle and consuming power?
Increasing the speed increases power consumption, this is an exponential function so if anything, lowering speed to 0.8 m/s may help extend your range.
I’d be interested to review a .BIN autopilot log from one of these 2 hours missions if you’d be willing to share it!
Sorry, how silly, I forgot to tell you that we are carrying quite a bit of extra weight, since we have a PC, an IMU, and a multibeam probe, which together reach almost 30 kilos.
Okay, so it would be a good idea to lower the speed a bit to see if we can reduce the consumption.
Thank you very much!!
To avoid dropping below 12V, how can I make it so that once it is seen to drop below 12V or whatever I set, the USV stays in loiter mode, for example?
Which parameter should I adjust?
Hi @Pulsar79 -
The ability to go to loiter mode as a failsafe is not present yet, but is coming soon! You can configure battery warnings on the Failsafe page.
It sounds like a majority of the vehicles power is going not to navigation, but payloads - the PC and multibeam likely more than triple the “hotel load” of power consumption at idle…
The efficiency of the vehicle is also reduced when fully loaded! adding additional buoyancy may not be a bad idea - what multibeam are you using?
This feature is included in ArduPilot 4.7, which was recently released as beta. If you’re willing to help beta test then you can install the Beta firmware and set the relevant failsafe to Loiter or hold (6), which attempts to loiter (if possible) when the failsafe triggers, and falls back to hold mode (i.e. “stop moving the motors”) otherwise (e.g. if there’s no valid position estimate).
Thanks to both of you! I will keep it in mind