Qgroundcontrol - Battery Indictor

Blue Robotics Products Batteries and Chargers
1

Hi,

I’m using the latest version of Qgroundcontrol to operate our Blue ROV 2 vehicle. I use Blue Robotics supplied LI-4S-15.6AH-R1 Lithium 14.8v 15.6AH batteries to power the ROV. My issue is that both batteries are fully charged prior to installation using the Blue Robotics charger. When I connect either battery to the vehicle the QGC software reports 100% charge, which confirms the BRC reading. The vehicle is deployed for Ops, but after approx. 10 mins of ops the QGC battery monitoring indicator drops from 100% to 0%. This happens with both batteries. I recovered the vehicle to check the battery status and in both instances the batteries were nearly 80% charged. Has anyone else experienced this type of issue before? I recharged both batteries to 100% and tried again, same result. Instead of recovering I continued operating for a further 20 minutes. I recovered the vehicle and checked the charge level. 68%.

I tested both batteries with similar results observed on the Battery Cell Checker. Readings listed below.

1S - 4.164V
2S - 4.162V
3S - 4.161V
4S - 4.181V

Are my batteries the issue or the QGC monitor? I’m leaning towards the QGC software, but I’m a novice when it comes to Lithium batteries. Probably a dumb question, but better to ask.

lee

2

Hi @Lcolville77 -
The issue is definitely related to QGround Control! You need to properly set your battery capacity within the program. To do so, go to Vehicle Setup by clicking the purple Q in the upper left, and select Power on the left. Set the capacity to the correct number of mAh (15600 or 18000, depending on your battery)
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Note - the vehicle assumes the battery is fully charged when powered on, so if you use half the battery and then restart the autopilot, the capacity readout will be ~50% inaccurate!

I typically prefer to set the capacity to -1, so I can monitor battery voltage directly, as mentioned here.

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3

Hi Tony,

Thanks for replying and providing me with a solution. Very much appreciated.

Kind Regard,

Lee Colville

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4

I spend most my time piloting things that crash to earth when battery dies. I trust raw voltage read out over any stat. I know my crafts Voltage sag. Doing this I always land at 3.8v per cell

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5

Agree, raw voltage per cell is the best indicator of when to recover to surface.

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