New build, old Pixhawk 1. Please help. Can only from from 16.5V to 15.8V


I bought my Pixhawk 1 in 2014. It had issues with SBUS in those days so I moved onto other projects. I am now back on the Pixhawk and kind of flying, 3 minutes at a time, but I have some issues. I am not sure if this is the correct group to post in. I will really appreciate any help. I will try to give as much info as possible.

This is the problem
When the 4S battery is full at 16.6V I can fly, but at soon as it hits 15.8V I start getting issues consistently. The left front motor has difficulty turning. Is that C2? Difficulty turning meaning when I lift off from the ground it doesn’t spin up, it just idles. I have to disconnect power and then slowly increase throttle. I might have to do this up to 10 times before the motor kicks in.

When I try another channel the motor does the same so it almost seems like the motor is broken, but it works fine when the battery is full power.

Full quad spec:
Firmware: 4.0.7 official
Weight: 1.2kg - 1.3kg depending on the scale I use
Motors: 4 x Rctimer 5010 530kv
ESC: Turnigy Multistar 4 in 1 31A
Battery: Zippy 2200 mAh 25C
Propellers: Hobbyking Slowfly Propeller 10x4.5
Pixhawk and accessories bought from in 2014:
1 x 3DR Pixhawk (SKU4725321)
Telemetry Kit 915Mhz
GPS uBlox LEA-6H GPS with Compass
The photo of the drone is in the dropbox folder with all the logs

This is the URL for the ESC

I have the RCTimer 5010 530KV motors

On the page, there is a table showing the pull of the motor(s). I don’t know if that is for one or for four motors. If it is for one motor then 14.8V and a 10 x 4.5 prop should give me 800g. That means at a lower voltage than what I am on I should have 3.2kg of lift. If it is for 4 motors then I should not be able to lift at all.

This is the battery URL. With 25C it should be able to deliver 55A. I am drawing less than 10A

I am thinking to try 6S but that is expensive because I need to get everything 6S from charger to battery to ESC’s and a Power distribution board so it is almost starting over.

The log I am using is 00000013.BIN up to the 3 minute mark. After that, the voltage drops below 15.8V and things go literally belly up. I checked the motors and ESC. Nothing gets hot.

The average current draw is 7.5A and max 9.14. The ESC should be able to supply 30A
Mag average values are X-0.05, Y-0.23, Z-0.4
Vibe average values are X 2.79, Y 5.79, Z 2.27
RCOU average values before issues C1 1593, C2 1636, C3 1531, C4 1552. Which motor is C2? Seems that one already has issues at the start.

RCOU average values when issues start just before the 3 minutes C1 1600, C2 1732, C3 1550, C4 1557.

Please help. Not sure what other information I can give.
Here is the dropbox URL again with all the logs and a photo of the drone

I take it you have performed the ESC calibration?

From this, I would say C2 is rear-left.


Thank you so they use that diagram for the numbering. I saw in another post someone said 1 and 2 was clockwise and 3 and 4 counter so wasn’t sure. I guess they also spoke about that picture

So this doesn’t make sense then. If we go by that picture my motor 3 seems to have physical issues but the logs say motor 2 is being pushed harder.

I did calibrate the 4 in 1 esc at full battery with mission planner and manual method as described in the manual. Full power then connect then disconnect and so on.

I also calibrated it at the reduced battery voltage in case that does something. I used mission planner and the manual method.

Without fail it has issues at 15.8V.

Looking at the battery voltage graph the voltage goes down linear so there isn’t a massive voltage sag. I also watch mission planner on the laptop while I fly. As soon as the drone starts lifting up the one side then the other side I look at the screen and the battery is at 15.8V.

I did a basic centre of gravity check by placing the middle of the drone on my finger and it balanced relatively fine.

I can go into loiter and Alt hold above 15.8V and it holds. Mission planner complains that it can’t go into those modes but it goes in. If I am in any of those modes at 15.8V the drone just falls out of the sky.

Post a link to a .bin flight log and turn off “Low RPM Power Protect” in the ESC settings from BLHelisuite.

The latest BLHeli suite can’t connect to the latest stable firmware.
I upgraded the firmware of my quad to the latest beta 4.0.10 I believe.
When click the button to read the ESC data it just says “found no valid ESC config”
When I click on verify BLHeli it shows again empty message boxes, no data and then it says connection to ESC1 failed.

I changed the parameters of the firmware
servo9_function 33
servo10_function 34
servo11_function 35
servo12_function 36

I also enabled servo_blh_auto 1

Mission planner complains constantly with IMU error in this version and BLHeli suite can’t find any valid ESC’s.

Can you please give me your older version of BLHeli suite? Then I can also go back to the stable firmware of the drone.