Flight autonomy of F450 drone about mrs_uav_system HOT 8 CLOSED

Hello, you can do this with Pixhawk settings, but you need to properly calibrate its voltage measurement correctly.
But I am not sure if this feature will work properly during autonomous offboard flight (we never tested that). We do not use this feature, we simply monitor the flight time and the lipo alarm, and land the drone when the battery is low.

The system will also land the drone automatically when the thrust needed for flight is over 80 percent of the max thrust, which will happen when your battery is dying. But you should never reach this far, as the battery will be damaged.

The battery voltage is also sent from Mavros to the onboard computer, so you can easily program a node that will monitor it and land the drone when the voltage is at a specified level.

Dan H.

from mrs_uav_system.

Hello, with a 4S 6750mAh battery, we get 10+ minutes of flight, dependant on the mass of the UAV.
Can you specify exactly what battery you use, what are the motors and propellers and what is the mass of the UAV?

And by the way, 4S battery should NEVER reach 12V, if it did, it is likely damaged. We set our lipo alarms to 3.5V/cell (14V for the whole pack), and when they go off, we land immediately.

Dan H.

from mrs_uav_system.

Hello @DanHert ,

thank you for the fast reply
I forgot to mention that , to power the NUC, we soldered a DC plug at the DC input of the Holybro Power distribution board. This DC plug is connected to the NUC power input.

For a drone of 2.35 kg (everything taken into account) , we use :

• battery : Rhino 4S 6000 mAhbattery
• Motors and props : Ready Tosky RS2312-920 and DJI propellers as mentioned on your website

Has the alert been setup in QGC or in the px4_config.yaml ?

Best,

Frank

from mrs_uav_system.

Hello, the alarm is an external one, like this:

It is plugged to the balance connector and it will beep loudly when the alarm voltage is reached.

Did you charge the battery fully? (to 16.8V). Is the battery new, or old? 2.35 kg is on the limit of the payload capability of this configuration, but you should still get more than 3 mins.

from mrs_uav_system.

Hello,

I am confused : isn't the max voltage for a 4S battery 14.8V ? As it is mentioned on the datasheet ?
When we charge, we go up to 14.8V-15V sometimes, but it won't go higher.

The batteries are 6 months old.

from mrs_uav_system.

14.8V is the nominal voltage (3.7 V per cell), but at this voltage the cells are less than 50% charged. You need to charge them to 4.2 V per cell for flight, that is fully charged. Learn more here - https://learn.adafruit.com/li-ion-and-lipoly-batteries/voltages

Dan H.

from mrs_uav_system.

Well well,

We made a misunderstanding, we will correct that. Thank you for your answers !

from mrs_uav_system.

Hello again @DanHert ,

I forgot to ask but to make the drone lands automatically when the battery voltage goes below 14V or whatever the threshold, what are the parameters and config files that I need to change ? (like min_voltage in
mrs_uav_general/config/px4_config ?

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