Current sensor issue

PX4 Autopilot
1

Hi all,
I am using Pixhawk UBEC Power Monitor Module 2-12S 200A current and voltage estimation for my VTOL. Each of the quad motor consume 30A current. During takeoff I get warnings of critical battery level, land now warning but using this current sensor as power module it is supposed to handle currents upto 200A.
Why am I getting is error? I am using Pixhawk 6C with PX4 firmware and set the source to power module as given the wiki/guide of px4 v1.16 “

BAT1_SOURCE (INT32)

Battery 1 monitoring source.

This parameter controls the source of battery data. The value 'Power Module / Analog' means that measurements are expected to come from either analog (ADC) inputs or an I2C power monitor (e.g. INA226). Analog inputs are voltage and current measurements read from the board's ADC channels, typically from an onboard voltage divider and current shunt, or an external analog power module. I2C power monitors are digital sensors on the I2C bus. If the value is set to 'External' then the system expects to receive MAVLink or CAN battery status messages, or the battery data is published by an external driver. If the value is set to 'ESCs', the battery information are taken from the esc_status message. This requires the ESC to provide both voltage as well as current (via ESC telemetry).”
2

@rroche any idea about how the issue can be fixed?

3

Hi there!
This indicates that your voltage is dropping too much: No tin the power module, but your battery! There is no indication on how your UBEC is doing.
Some VTOLs have a undersized battery, which during takeoff can dip quite a bit - but that would be a hardware issue, and should not happen on takeoff (but maybe when landing with a low battery).

Could you paste a log, or check the voltage level in the log, to verify what the voltage is doing?

4

Sorry for the delayed response.
Here is the log of my recent flight
https://review.px4.io/plot_app?log=d4f2b663-9343-4375-b358-f62c495d4227
I’m still getting the same issue.
I am using HRB 5000mAh 50C 3S batteries (3S+3S). Its a 8kg VTOL
Thanks

5

I assume you are using a 6S configuration, so two 3S in Series.

In the log, the batteries start of at around 24V, which is resonable.
As soon as the load is applied, the voltagte drops to around 19V.

A slight drop in voltage is normal, however, this seems a bit extreme to me.
Could it be that:

  1. You are using old and worn out batteries?
  2. You are using low quality batteries, that cannot actually do what they claim?

Most likely, this is not a problem with the Power Monitor, but your batteries.

6

Yes I’m pretty sure the batteries are old and worn out. We’ve used the same batteries for last 4-5 years so I’m guessed its mah capacity has decreased to significant level.
Yeah may be its a low quality battery but I’m not quite sure how good HRB batteries are

Thank you very much. I’ve decided to change my batteries. The hover of my VTOL is quite good but the avionics system become quite hot to the point that I can’t remove even the xt60 connectors after landing and need to wait for couple of minutes for system to cool down. I’m suspecting this to be issue related to battery you have pointed out