Mavic Pro restoration project

Deleted member 161693 · Mar 18, 2022

Hi !
I bought a cheap secondhand Mavic Pro M1P with a few issues, history unknown, and took the challenge to fix it in order to have fun with a drone while being broke.
The purpose of this thread is to regroup all known issues and fixes in case somebody needs them.
Here we go:

-Rear arm platic stopper tab on the hinge was broken.
Part is here 8.17US $ 22% de réduction|Arbre de bras arrière gauche droit pour Drone DJI Mavic Pro, pièces de rechange, accessoires de réparation | AliExpress (the cheapest I could find, it fits)
This video explains what needs to be done
-Fan was not working, and device was overheating.
Part is here 6.82US $ 15% de réduction|Pièces de rechange pour ventilateur de refroidissement DJI Mavic Pro, accessoires originaux pour Drone | AliExpress (again, the cheapest I could find)
This video contains a part whith the useful information After swapping the fan, it was still not working. The new fan was working when applying 4V DC. I wondered if previous owner had played with the firmware at some point.
I reflashed the latest firmware: nothing
I made a factory reset with DJI assistant: SUCCESS !
I was a bit puzzled but still happy. Previous owner probably tried to hack the drone.

-RC could not connect no matter what I tried (went through quite a few documents and videos)
Flashed the firmware on both RC and drone: SUCCESS !

-Gimbal often reported N/A in the app. I can't access settings or calibration. Most of the time, the gimbal menu is there when the drone is cold, I can access settings and calibration, but then it vanishes when the drone starts heating, after a few minutes.
-I changed thermal paste (quite cracked and brittle from overheating probably) in order to improve cooling - no effect
-I read some people had this issue after FW upgrade, so I tried downgrading (both RC and drone) with DJI assistant: no effect. I tried downgrading to earlier versions with DUMLdore, but it failed. Went back to latest firmware. Still nothing.
The gimbal initializes properly, and I can do tilt/pan from the RC.

-SD card reported as N/A in the app, except when the drone is cold. Sometimes, even when shown as missing, it mounts on my PC plugged on USB.
-Not related to SD card. I've tried many, including ones that work in a friend's mavic pro.
-I tried cleaning the SD port with a duster and some contact cleaning spray - no effect

-No chime sound on startup. I can live with it.

I wonder if the main board has suffered from either a crash or overheating. There's a guy close to my place who is able to do chip reballing (mostly for game consoles) in his workshop. But I'd like to understand which chip to work on.
Issue with gimbal N/A doesn't seem related to the gimbal or the camera, as they both work, but rather with the management interface that probably goes through a different wire/chip. I wonder if it could be a consequence of firmware tampering. I'd like to rule out all possible software causes before trying hardware. Hope is low as it seems temperature-related, but still work a try.

-> Is there something I can learn from system logs ? I've read a few of them but didn't find anything meaningful. fatal.log says things about module auth gone wrong, and 'fail to get buf for vision' service but that doesn't mean anything to me.
-> What else do you suggest ?

Regards

MAvic_South_Oz · Mar 18, 2022

Good luck with it, at least most parts are still around for the M1P, and plenty of tutorials.

It's really difficult with multiple issues going on.
Even a drone repair type place would likely swap out this, that, and see if problems are fixed, if not, try something else relative.
Can get expensive and time consuming / frustrating.

If you have the time and parts required are cheap enough, a great 'while being broke' project.
When all is good, these are a great drone, still fly mine since ownership in 2017.

lookout · Mar 19, 2022

The broke fixing the broken.

lookout · Mar 19, 2022

Probably need to replace the gimbal ribbon cable.

CaptainMavic · Mar 19, 2022

My M1P was sold for parts. I was also on a budget. I pride myself in being able to fix just about anything. I also had gimbal over load message but camera worked. The gimbal would do nothing. It turned out that the gimbal ribbon cable was damaged where you couldn’t see it. Replaced the cable, recalibrated it and now everything is good. This cable is the weak link in the system and I would replace it before trying anything else first. Good luck the MP is a fun bird to fly!

Deleted member 161693 · Mar 22, 2022

Sometimes the gimbal produces a weird buzzing sound. I can stop the vibration by slightly moving the camera with my fingers. I read somewhere that it's related to the ribbon cable, so I ordered one and see if it solves the issue.

CaptainMavic · Mar 26, 2022

Let us know if this resolve’s your issue. Be careful to properly install the ribbon cable. There are some very tiny screws that are easy to lose. Be sure to carefully and completely snap the cable connectors in place.

Deleted member 161693 · Mar 27, 2022

My order is on the way.
What I have received is some liquid rubber from aliexpress, to replace the sealant that I had removed when I replaced the rear hinge. 1.11US $ 43% OFF|30/50ml Liquid Insulating Tape Repair Rubber Electrical Wire Cable Coat Fix Line Glue Waterproof Seal Temperature Resistant Past| | - AliExpress
I didn't want bathroom-grade silicon as its curing is corrosive, but this one is way too liquid. I wouldn't recommend.

CaptainMavic · Mar 27, 2022

I’m a automotive mechanic, so I just used what I have. Automotive grade silicone gasket sealer worked great for me.

MAvic_South_Oz · Mar 27, 2022

Neutral cure silicone should not harm anything, that's made for metal guttering etc.
The glass type silicones are acidic curing, smell like vinegar, and yes they are very corrosive to metals and mirror backings etc.
I'm sure there would be a lot of inert materials out the that could suffice, the liquid rubber product sounds interesting, and I'm sure the auto gasket silicone would be safe too.

Deleted member 161693 · Mar 30, 2022

Hi
While waiting for my gimbal ribbon, I tried to fix something else. One of the batteries was faulty. It responded but blinked 16 times (common fault apparently).
So I disassembled the plastic case, which is a bit difficult.
Then I plugged out the small white connector and unsoldered one of the thick wires that connect the battery to the board.
I measured the voltages: 2.1V, 1,87V and 2.06V. Bad, but not too bad, according to this guy Restoring/Recharging Over-discharged LiPo (Lithium Polymer) Batteries!
I took my Riden RD6012 power supply and began charging the batteries one by one. voltage: 4.2 current 0,05A (very low) just to see how they reacted. I used the power supply's external thermal probe that cuts the power if some threshold is crossed. The voltage started to increase. At 2.5V I set the current to 0.1 A and I stopped when I reached 3V per cell. Once I stopped charging, the voltage dropped back to around 2.89V per cell. All 3 cells behaved the same way.
So I decided to charge them all in the same time.
I set the voltage to 12.6V (3x4.2) and current to 0.1A which I increased little by little on the way, stopping around 1.2A when the battery was around 12V. Voltage kept increasing until 12.6V then at some point the battery started drawing less current, which is standard LiPo behaviour. When that current was around 0.1A, I stopped. The temperature measured by the probe never exceeded 19°C.
I soldered the wire to the board, and plugged in the small white connector. Now the battery behaves normally. Pressing 2 times starts the battery and shows the charge level with the led ramp instead of a single one blinking 16 times. I was quite happy.
But It doesn't start the drone. I'll check the connectors tomorrow.

CaptainMavic · Mar 30, 2022

The battery has a smart battery fuel gauge board. If the cells voltage gets too low, if the cells are disconnected, or if the balance plug is disconnected, the battery monitor will set a “ permanent failure”. No voltage will be output from the connector and you will not be able to charge through the connector either. The only way to reset the battery monitor chip is with a laptop computer, a EV2400 interface module, and the Texas Instruments bqEVSW software. The chip can be reset (I have the necessary equipment), but it really isn’t a do it yourself by the average Joe kind of thing. The possibility of a battery explosion and fire are really possible. And there are still questions as to the reliability of a reset battery. Don’t want your drone falling out of the sky and crashing through someone's windshield. There are lots of ways to supposedly reset the battery on the internet, but none of them actually work, other than what I have described above. Wouldn’t want to burn down the house, destroy the drone, or worse yet hurt someone, when a new battery can be purchased for $65-$70 bucks from Amazon.

Deleted member 161693 · Mar 31, 2022

I begin to realize that some suggested fixes from the internet don't work.
I happen to have a raspberry pi. I may try "comm_sbs_bqctrl.py" script. CaptainMavic, Have you tried it ?
Otherwise I'll use the battery for something else.

CaptainMavic · Mar 31, 2022

I’ve saw it done with other interface boards on YouTube, but haven’t tried it myself. Search for videos on how to reset the chip with raspberry pi. One hint, don’t solder wires onto the board as the pads come right off. I use probes held in a jig to make contact with the connection pads on the board.

Deleted member 161693 · Mar 31, 2022

Thanks for the advice that came right on time, as I was just about to solder wires. I'll use probes.
My raspi is ready to go. I'll tell you if Mefistotelis' method worked for me.

CaptainMavic · Mar 31, 2022

Good luck resetting it. Follow the procedure to the letter. Don’t change anything else as changing any of the other data items can cause problems. I managed to bring quite a few batteries back to life. Most of them had less than 20 charge cycles on them but went into permanent failure from sitting too long.

Deleted member 161693 · Apr 3, 2022

I succeeded in resetting Permanent Failure flag using Mefistotelis method described here:
This is impressive. It just works.
There were a few minor differences from his video.
-i2c baudrate was not set in /boot/config.txt, so I typed them and rebooted
-I had to install several things to get the script working
>git clone "https:/ /github.com/o-gs/dji-firmware-tools" (the scripts)
>sudo apt-get install python-smbus
>sudo apt-get install i2c-tools
>pip install smbus2
not needed: pigpiod -s 2 as I didn't get the error he mentioned at some point
and then
>sudo i2cdetect -y 1
>> detected my battery with the same address 0x0b
>./comm_sbs_bqctrl.py -vvv -dev_address 0x0b read BatteryStatus
>./comm_sbs_bqctrl.py -vvv -dev_address 0x0b --short monitor BQLifetimeDataMA
>> this command returned a different layout, with less information
>./comm_sbs_bqctrl.py -vvv -dev_address 0x0b sealing Unseal
>> showed PERMANENT_FAILURE: 1=Active
>./comm_sbs_bqctrl.py -vvv -dev_address 0x0b trigger PermanentFailDataReset
>./comm_sbs_bqctrl.py -vvv -dev_address 0x0b sealing Seal
>> showed PERMANENT_FAILURE: 0=Inactive

Now the battery works. It charges, and turns on the drone.

While playing with LiPo battery can be dangerous, I believe I didn't take too many risks, as I succeded in first cell revival to achieve a stable and balanced cell voltage. Just in case, all cell charging was done on the kitchen floor, on an spare ceramic tile that I had, and with a fire extinguisher at hand.

The most difficult part of battery revival is the mechanical part
-How to disassemble the pack without destroying it (some parts are glued)
-How to make electrical connections to the board without any soldering
-How to reassemble the pack and make it look good. Aliexpress sells battery shells for 15€ but it defeats the purpose of a cheap repair.

First flight will be close to the ground above a mattress, with a conservative warning level, just to see if the voltage suddenly drops.

I also found a good rubber sealant: It's called 704 rubber sealant on aliexpress.

CaptainMavic · Apr 3, 2022

I use one of those soldering helper tools that have the multiple alligator clips on arms. I use wires with needles soldered onto them, and use shrink tubing to insulate them. When positioned properly they made good contact and the reset was possible. The very first battery that I soldered wires to, I barely touched them and the pads fell off the board. I managed to reset the board but not on the missing pads. I spent weeks of spare time researching how to bring the first battery back to life and tried all the supposed fixes, none of which worked. I saw the same video you used, but didn’t have the raspberry pi board. I was able to get a EV2400 at a reasonable price. It does take some work to get the case open without destroying it. Cycle the battery from full charge to discharge (no lights on) several times to condition the battery and calibrate the battery monitor. I have a adapter to plug into the battery to use it like a power bank. Hooked up the iPad to it and ran the battery down that way instead of using the MP. Now using the GO4 app, the cell balance is normal. Check that the battery will self discharge to 50-60% on its own. Check monthly that the charge hasn’t gone down below 50%. If it has, just charge it until the third led comes on. Fortunately I have a pretty good background with electronics and computer stuff. There is a certain amount of satisfaction in bringing something back to life. Glad you had good luck and fun learning how to do this.

Deleted member 161693 · Apr 3, 2022

Ok and I received my gimbal ribbon.
Replacing it is quite annoying, so a bit of patience is needed. I found a good practice that once you remove it, you use the old cable to figure out how to install it back. Then you bend the new ribbon and install it.
But this didn't solve the issue: the gimbal status goes N/A (and SD card disappears) after a few seconds of uptime.
I noticed that during boot, the gimbal makes fewer violent noises (clac-clac). Just one instead of two or three. Is there a possibility that I damaged the new ribbon ?

Deleted member 161693 · Apr 3, 2022

For battery probe points, I used a part that I removed from an old hard disk, to make contact between the board and the motor. it had those little gold-plated springs that I just needed to place and hold with a clothespin, and it worked.
The usb adapter is a good advice. I'll borrow one from a friend to allow the battery to cycle several times.
But what I intended to do with the drone, is to download the flight log, in order to be able to get a graph of battery voltage VS time. Do you know a more convenient way of doing it ?