Incorrect Voltage Warning

I am currently reciveing the following error whenever I plug in a set of batteries and connect to the system: “CRITICAL: Caution Avionics power low: 4.74 Volt”. The voltage portion changes whenever I unplug and re-plug in batteries.

My drone uses 2 6S batteries per flights. I have 3 sets (6 total), and all are spitting out that same error. The batteries are fully charged. When I checked, all 6 cells read 4.20 V and even QGroundControl recognizes that my batteries are at full capacity (100%) and ~25 (25.something) volts.

After plugging and unplugging a set of batteries 5-6 times, I got the error to go away. I flew the drone for 20min, landed for a battery swap, and got the warning again. I have not flown when I receive the warning, so I don’t know if the behavior of the drone would change.

What is the issue, and what do I do to address it?

It’s not the battery.

Are you using a pixhawk 1 from a unknown or cloned brand? That generally is it. Either power module bec or onboard voltage regulator isn’t to spec and current is too low dropping down voltage or voltage is actually is too low. I don’t remember if by powering from a higher current external bec to the servo rail it bypasses it but generally that’s what’s going on.

@david_s5 could chime in if power can be provided without using the onboard 5v Ldo.

What HW is this on?
Measure the “5V” at the Power Module Outer 2 pins on the connector. It should be ~5.3V. Is it?
Do this with the PM connect to the FMU and not connected. Then check both ends of the cable, while connect. Is it the same in both places. What does it measure?

Also never power from a servo rail. It is too noisy of a source and can an issue.

Let us know

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Thank you both for your responses. I am very new to drones as I use it for my job, so I appreciate your patience and suggestions.

My drone is custom built by a company, but I don’t believe the Pixhawk 1 is off brand or out-of-date. I also do not think it is powered from a servo rail. I have also contacted the company regarding the issue to see what their engineers suggest.

What would I use to measure the voltage on the Outer 2 pins? Would it be a multimeter?

Are these hardware specs relevant? What specs would you like me to provide that would be of use?:

  • (Flight Controller): Modal AI Flight Core
  • (Remote control software): OpenTX
  • (Operating software): PX4 (Modified Quadrotor 4001)