Author Topic: DJI mavic battery repair  (Read 5078 times)

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Offline lartsu

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DJI mavic battery repair
« on: July 17, 2018, 10:34:03 am »
My current project is DJI Mavic battery.

The battery was not working because the cells were not in balance. Now the cells are in balance (3.7 V/cell).

For some reasons the DJI mavic charger is not charging the battery. When connected to charger the battery is repeating the following sequence: the  LED1  is blinking ~16 times in 6 sec. and then ~7 sec break.

Do you have any ideas how get battery back to charge and life?

Some of batteries have printed labels on back side of it.  What they are  and are there any use for them (RST)? (image from mavicpilots forum).

« Last Edit: July 17, 2018, 02:26:52 pm by lartsu »
 

Offline Zucca

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Re: DJI mavic battery repair
« Reply #1 on: July 17, 2018, 10:47:44 am »
First you need to know if the problem is in the battery or in the charger.

To you have a DC load to test how the battery performs in discharging?
And do you habe a Lab power supply to check how the battery performs in charging?

The DC load can also be used to check the charger.

A second known ok charger or  battery can also be helpful.


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Online wraper

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Re: DJI mavic battery repair
« Reply #2 on: July 17, 2018, 11:05:16 am »
I see there is BQ.... controller on the PCB. Once fault is detected, it gets locked. You cannot simply reset it.
 

Offline Zucca

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Re: DJI mavic battery repair
« Reply #3 on: July 17, 2018, 11:15:15 am »
I see there is BQ.... controller on the PCB. Once fault is detected, it gets locked. You cannot simply reset it.

Interesting.
Looked at BQ24703 and BQ24650 datasheet, I could not find such a lock feature.
How do you unlock it?
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Offline lartsu

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Re: DJI mavic battery repair
« Reply #4 on: July 17, 2018, 11:21:48 am »
The charger is fine - it charges other batteries.

The chips are bq30z55 and MSP430.
 

Offline Zucca

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Re: DJI mavic battery repair
« Reply #5 on: July 17, 2018, 11:59:42 am »
Use the DMM with a good and and the bad battery to understand where the difference is under charge.
90% the battery is bad, and there is no fix for it.

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Online wraper

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Re: DJI mavic battery repair
« Reply #6 on: July 17, 2018, 12:05:50 pm »
I see there is BQ.... controller on the PCB. Once fault is detected, it gets locked. You cannot simply reset it.

Interesting.
Looked at BQ24703 and BQ24650 datasheet, I could not find such a lock feature.
How do you unlock it?
By stolen authentication key.
http://www.ti.com/lit/ug/sluu852/sluu852.pdf
Quote
The device uses SHA-1 one way has function for device authentication by host system. Unseal or Full
Access mode is also protected using SHA-1 authentication.
 

Online wraper

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Re: DJI mavic battery repair
« Reply #7 on: July 17, 2018, 12:12:30 pm »
AFAIK there is expensive software to reset this chip in laptop batteries but I doubt they support DJI batteries. In any case it's not cost effective in low quantities.
 

Offline lartsu

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Re: DJI mavic battery repair
« Reply #8 on: July 17, 2018, 01:41:53 pm »
Thanks for providing more details.

BTW - Do you have any clue what RST contact on back is used for?

 

Offline Zucca

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Re: DJI mavic battery repair
« Reply #9 on: July 17, 2018, 02:14:06 pm »
picture?
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Offline lartsu

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Re: DJI mavic battery repair
« Reply #10 on: July 17, 2018, 02:23:38 pm »
In the first message ( battery.jpg).

If the chip is replaced to new does this clear the situation?
« Last Edit: July 17, 2018, 02:26:30 pm by lartsu »
 

Online wraper

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Re: DJI mavic battery repair
« Reply #11 on: July 17, 2018, 02:36:10 pm »
If the chip is replaced to new does this clear the situation?
It needs programming
 

Offline Zucca

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Offline lartsu

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Re: DJI mavic battery repair
« Reply #13 on: July 17, 2018, 04:17:39 pm »
Any ideas what are these test pads on the circuit board?

 

Offline Zucca

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Re: DJI mavic battery repair
« Reply #14 on: July 17, 2018, 04:26:27 pm »
Those are test pads for production. By connecting the board with the line production equipment they make sure the board is ok.
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Online james_s

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Re: DJI mavic battery repair
« Reply #15 on: July 18, 2018, 12:38:57 am »
Sounds like one more reason to avoid DJI. My multirotors use standard "dumb" LiPo packs, nothing in them to prevent me doing whatever I please. Of course the safety responsibility is strictly on me too.
 

Online wraper

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Re: DJI mavic battery repair
« Reply #16 on: July 18, 2018, 01:02:42 am »
Of course the safety responsibility is strictly on me too.
DJI is not a small company located in garage, you can be pretty sure that shit will fly the first time when it burns someone's house. Actually it does a darn good job in this case. Preventing using battery with problem in the cells.
 

Online james_s

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Re: DJI mavic battery repair
« Reply #17 on: July 18, 2018, 01:04:56 am »
Generally it does, although I saw a video from a of a DJI battery that was sitting on a workbench back behind some guys who were filming a video on another topic spontaneously catching fire. By the time somebody noticed the smoke and turned around the thing had burst into flames. Stored energy is dangerous, no way around that.
 

Offline lartsu

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Re: DJI mavic battery repair
« Reply #18 on: July 21, 2018, 11:20:33 am »
Now the Battery Pack Manager (bq30z554) has been bypasses.  The battery leads have been connected directly to external connector. Also the battery type have to change to non DJI battery via DJI assistant software.  You will need the older version from DJI assistant to switch the debug mode on to change the battery type.

The battery manager is still sending at least the cell voltages and temperature to the remote controller.

Probably it's not the safest to charge battery from DI charger... I added separate connector to external charger.
 

Offline ronimarquestc

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Re: DJI mavic battery repair
« Reply #19 on: April 02, 2020, 01:34:42 pm »
what software do you use to unlock batteries together with the ev2300?
 


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