Motors won't spin past 12% for 5 seconds with props on 'Test all motors' on Mission Planner

Hardware Pixhawk family
1

Hi everyone,

My name is King, and I’m currently building my first autonomous multirotor. I’ve been trying to get it flying, but I’ve run into an issue that I haven’t been able to solve despite a lot of troubleshooting.

The problem occurs during the Mission Planner Motor Test. With all motors selected, they will not continue spinning beyond:

  • 12% throttle for approximately 5 seconds with propellers fitted, or

  • 14% throttle for approximately 5 seconds without propellers.

After around 5 seconds, all four motors stop simultaneously, and the ESCs play their startup tones as though they have rebooted before reconnecting. The Pixhawk itself remains powered and does not reboot.

Hardware

  • 4S power system

  • CNHL Racing Series 8000mAh 4S 120C LiPo battery

  • Pixhawk 6C Pro flight controller

  • Pixhawk PM02 power module

  • Matek PDB HEX 2–12S

  • Autoro AS100 anti-spark switch

  • EC5-to-XT90 battery adapter

  • AM32 50A ESCs

The main power rail is shown in this short unlisted video:

https://youtube.com/shorts/3A-KjVtys30?feature=share

Here is another video demonstrating the issue during the motor test:

At the moment, I suspect there may be a problem with the main power distribution, such as a voltage drop, intermittent power interruption, or another issue affecting the ESC power rail. To rule out software restrictions, I have already disabled the relevant Mission Planner safety settings (including BRD_SAFETYOPTION) that would otherwise prevent motor testing.

This drone is intended to be fully autonomous, so I am not using an RC transmitter. My project partner and I plan to implement software-based control once the propulsion system is operating reliably.

As this is my first custom drone build, I’d really appreciate any suggestions on what to check next or whether there’s anything in my power system or setup that stands out as a likely cause. If additional information would help, I’m happy to provide wiring diagrams, photos, logs, or any other details.

Thank you in advance for your time and advice.

2

That’s some old firmware. Update to latest Stable before advancing.
What Messages were displayed on the Messages Screen during “Test all Motors”
Post a link to a log created by Motor Test.

1 Like
3

I think that’s a good guess myself. Can you share a picture of the power distribution hardware you’re using?

The battery looks plenty big enough. Is that a 6S LiPo? How many mAh? Is the battery relatively new and does it hold a charge well?

I personally think that’s not a good combination.

I think you’re making troubleshooting harder by not having a RC option.

Make sure you follow the advice from @dkemxr.

1 Like
4

Agree. I would say for configuration and tuning one is mandatory.

5

Yes, for configuration and tuning a RC controller is safer and more flexible. And hence, mandatory.

6

If you don’t already have a RC transmitter, you might want to read the discussion in this thread about peoples’ favorites. The RadioMaster TX16S MK III gets high praise from several trusted forum members. I personally prefer the lighter weight of the GX12. Both these radios are dual band and capable of using the newest dual band ELRS receivers. The RadioMaster Pocket seems to be a favorite inexpensive transmitter (based on a number of YouTube videos I’ve watched (GizFPV used a Pocket)). Of course the least expensive option is a radio you already have.

As others have stated, setting up your quadcopter to use ArduCopter will be easier if you have a RC control link.

Some ELRS radios can act as a MAVLINK bridge between your PC and your aircraft. I use this feature myself.

1 Like
7

Ok, I will do that first and let you know

8

Thanks for the recommendation. I will look into an RC controller- the RadioMaster TX16S MK III does look pricey, might go for the RadioMaster Pocket as mentioned. As for the question before, the battery is 4S LiPo 8000mAh, and here are some photos of the setup:

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Please also refer to this video for a walkthrough of the setup: https://youtube.com/shorts/3A-KjVtys30?feature=share

As I mentioned before, I suspect it could be a power related issue like voltage sag caused by poor solder joints or the battery itself. If you can have a look at some of these photos and offer some advice on how I can fix this issue, that would be much appreciated. Thanks for your recommendations once again!

9

I think it might be an issue with the motor and ESC combination.

The FC does not power off, but only the ESC seems to be rebooting. So it looks like the ESC may not be able to properly supply the voltage or current required for the motor to spin.

Is it possible to check the ESC and motor specifications as well?

10

The PMU position looks a bit unusual.

From the photo, it seems to be connected in this order:

Battery > Anti-Spark Connector > PDB > PMU

Or it also looks like the PMU might be installed in the wrong direction.

Could you please send a photo showing how the PMU is connected?

11

Pretty much all ELRS radios and modules can, AFAIK the only exceptions are STM32 based hardware (support dropped some time ago) and a few very early internal modules without a backpack (rare).

12

I think some of the older 900MHz receivers offer poor performance when used with MAVLINK. The data rate can be very low. As you suggest, the new stuff should work fine.

13

After rewatching your video, it sure seems like you have a power problem. I don’t know if you have a connection problem or a battery problem. You didn’t mention how old the battery was. Do you have a way to test the health of the battery? Many chargers can test capacity and also internal resistance.

Your soldering reminds me of my soldering when I first started soldering. I see multiple layers of solder on some of the joints (this is not good). The first photo shows one of the power connections coming uncomfortably close to the “S1” pad. Most of the power connection’s solder joints look sketchy to me. I believe your power distribution board was designed to be used with thinner wire. I’m pretty sure the wire being soldered to the board is supposed to fit inside of the provided holes. Power wires soldered only to one side of a PCB are usually provided with a solder pad at the edge of the PCB.. The pads/holes on your board are intended for through hole soldering. I also see a lot of solder on top of the solder mask. I know from painful experience that solder mask can’t be trusted to provide consistent insulation.

The connector adapter shown in your third photo could also be problem. I’ve certainly resorted to plug conversions myself but It’s generally best to use the fewest connectors in series as possible. If that were my setup, I’d replace the battery pack’s connector with a XT60.

I’d also suggest leaving the current sensing board out while testing. This would reduce connecters in series and make the system simpler for testing. Of course being able to monitor the current could be helpful in diagnosing your problem so you might just want leave the sensor out for a couple to tests just to eliminate it as the culprit.

Your setup looks kind of big for a 4S system. Is there a reason you didn’t go with 6S? There might not be anything wrong with using 4S on your quad. It just looks off to me. A 6S setup would let you use thinner wire with lower current while maintaining the same power delivery. Again, I’m not at all sure this is really an issue.

Good luck figure out the problem. I hope you keep us updated on your progress.

(FWIW, I hate vertical video. Yes, I am a grumpy old man.)