Battery mod thread

[Justinswidebody]

I have 3 magic bms boards that have all quit working within a week of one another.... I'm wondering if anyone else has had the same problem who has tried this method.....

I'm thinking dji is doing something sneaky behind our backs

 

[lalanomana]

I have 3 magic bms boards that have all quit working within a week of one another.... I'm wondering if anyone else has had the same problem who has tried this method.....

I'm thinking dji is doing something sneaky behind our backs

The 1.06 apps asking me to update the battery firmware, perhaps you did the update? Or maybe the 1.06 is checking something on the battery, try u older version of fly app...

 

[Justinswidebody]

The 1.06 apps asking me to update the battery firmware, perhaps you did the update? Or maybe the 1.06 is checking something on the battery, try u older version of fly app...

I stay on the original fly app. .100

 

[aeromedved]

I have 3 magic bms boards that have all quit working within a week of one another.... I'm wondering if anyone else has had the same problem who has tried this method.....

I'm thinking dji is doing something sneaky behind our backs

When plugging and unplugging the balance connectors that you used for the magic boards there's no defined order in which the pins make contact. It is possible that as you unplugged the balance lead, the center pin got disconnected earlier than the other two and BMS read the 1st cell as being at 0v, setting the "bad cell" flag.

To avoid this problem I make some pins longer on my builds that are sensitive to the connect/disconnect pin order. Look at the MM battery connector on the drone, two ground pins are longer than others.

 

[everBit]

two ground pins are longer than others.

It's just an measure for ESD protection of SMBUS line.
It's general solution for many ESD-sensitive applications like USB ports etc.
When Ground wires come in contact first then unwanted surface charges and transients are minimized.

 

[Justinswidebody]

When plugging and unplugging the balance connectors that you used for the magic boards there's no defined order in which the pins make contact. It is possible that as you unplugged the balance lead, the center pin got disconnected earlier than the other two and BMS read the 1st cell as being at 0v, setting the "bad cell" flag.

To avoid this problem I make some pins longer on my builds that are sensitive to the connect/disconnect pin order. Look at the MM battery connector on the drone, two ground pins are longer than others.

That's a interesting conclusion.... However the LEDs don't give any led faults. It shows full battery... Even the 3 bay fly more charger will show full battery but then all the LEDs shut off instead of stay on like the other batteries.

 

[aeromedved]

It's just an measure for ESD protection of SMBUS line.

Exactly. I used those pins as an example.

That's a interesting conclusion.... However the LEDs don't give any led faults. It shows full battery... Even the 3 bay fly more charger will show full battery but then all the LEDs shut off instead of stay on like the other batteries.

Interesting, do the drone LEDs indicate full battery on a short press but it doesn't turn on with a long press?
If that's the case see what you get on the battery connector, does it have the correct voltage on the "+" and "-" pins? Does it stay within adequate range when load is applied?
My completely stock MM turned on and booted fine when I connected power from a bench PSU directly to the "+" and "-" pins of the battery connector without any BMS, but refused to take off complaining about battery communication.

 

[Justinswidebody]

Exactly. I used those pins as an example.



Interesting, do the drone LEDs indicate full battery on a short press but it doesn't turn on with a long press?
If that's the case see what you get on the battery connector, does it have the correct voltage on the "+" and "-" pins? Does it stay within adequate range when load is applied?
My completely stock MM turned on and booted fine when I connected power from a bench PSU directly to the "+" and "-" pins of the battery connector without any BMS, but refused to take off complaining about battery communication.

No it only shows the battery status when you plug the mini in to charge... If I have a battery they is half charged it will display a half charged battery and act like it's charging it... Only on the mini... If I do this in the 3 bay battery charger it just displays the battery level and will not charge it...

I don't get any power from the pin outs.

 

[aeromedved]

No it only shows the battery status when you plug the mini in to charge... If I have a battery they is half charged it will display a half charged battery and act like it's charging it... Only on the mini... If I do this in the 3 bay battery charger it just displays the battery level and will not charge it...

I don't get any power from the pin outs.

Looks like either the controller considered the battery unsafe and disabled power FETs or it got zapped with static as it possibly wasn't ESD-hardened on the cells side because DJI did not expect someone to use the board this way

You can jump the power FETs and see what error the drone throws when it boots.

 

[Justinswidebody]

Looks like either the controller considered the battery unsafe and disabled power FETs or it got zapped with static as it possibly wasn't ESD-hardened on the cells side because DJI did not expect someone to use the board this way

You can jump the power FETs and see what error the drone throws when it boots.

I've done that before and it won't throw a error until you start the motors... Then you will get a system power error... Either way it's toast unfortunately... I'll either make another one or move on from the mini...

 

[aeromedved]

I've done that before and it won't throw a error until you start the motors... Then you will get a system power error... Either way it's toast unfortunately... I'll either make another one or move on from the mini...

Alright, so the BMS does communicate with the drone. When jumping the FETs you might've jumped the current sensor as well, if there is one on the board.
At this point it is more screwing around than troubleshooting

Edit: did you try to update the firmware on the bad BMS? If it is going to the trash can anyway it might be worth a try, for science.

Edit #2: did the app display the battery temperature and voltage for each cell when you booted the drone with a hotwired bad BMS?

 

[Justinswidebody]

Alright, so the BMS does communicate with the drone. When jumping the FETs you might've jumped the current sensor as well, if there is one on the board.
At this point it is more screwing around than troubleshooting

Edit: did you try to update the firmware on the bad BMS? If it is going to the trash can anyway it might be worth a try, for science.

Edit #2: did the app display the battery temperature and voltage for each cell when you booted the drone with a hotwired bad BMS?

Yes I've tried to update firmware with a bad bms and it didn't fix it...

Before trying to start the motors yes... After that no... After trying to start the motors the data terminals no longer display any voltages

 

[aeromedved]

Yes [...]

You've checked everything that could be checked. I don't think DJI did something if they didn't fail all at the same time. The MCU seem to be alive, not sure about the battery gauge IC. since you were using the .100 firmware version it is possible that it doesn't report all the fault flags that could be set.

It's sad that the magic boards failed. Whoever decodes the comm protocol can make some $ selling the magic boards based on a $2 MCU for DIY packs.

 

[everBit]

After trying to start the motors the data terminals no longer display any voltages

It looks like a hardware or power issue. Even firmware-blocked bms continues communicate on signal bus normally.

 

[Justinswidebody]

I think I know what the issue is... I think if you leave it unplugged for so long that the capacitor looses it's charge and the bms goes dead and thinks it's bad... Probably should keep a battery plugged into it at all times

 

[Dicky4480]

I saw the latest video from "Fly Far and Wide" on Youtube, where he landed the mini over 14 km away from the home point. The interesting thing is how the craft looks like with the modded battery as he did mod the belly and rear of the drone to accommodate the extra batteries. I also looked at a previous video where the case was still intact (belly + rear) and posted pictures below.

It looks like the Mini has a Stock battery or at least the electronics (Magic board) and on each side he strapped two 2S LiPo's.
Found this info in the comments 1 x 1100mAh, 2 x 1480mAh

Pictures below from this video

View attachment 91519

View attachment 91520 View attachment 91521

And from this video

View attachment 91522 View attachment 91523
View attachment 91524 View attachment 91525

Yea he’s swapped out the li-ion battery for a lipo, he also has one of the Japanese MM lipos

 

[Marcuchinonis]

I have 3 magic bms boards that have all quit working within a week of one another.... I'm wondering if anyone else has had the same problem who has tried this method.....

I'm thinking dji is doing something sneaky behind our backs

Two for me. “Battery cell error”. The drone switchs on, but the error message doesn’t let to fly. Something is Diferent from two weeks ago, but I don’t know what.

 

[Justinswidebody]

Two for me. “Battery cell error”. The drone switchs on, but the error message doesn’t let to fly. Something is Diferent from two weeks ago, but I don’t know what.

Have you left the board unplugged for a while?

 

[Marcuchinonis]

Have you left the board unplugged for a while?

Hello. I have not. But with the first two briked bmss, I can not switch on the dron. With the last two, I can switch on the drone, but the "battery cell error" don't lets me fly. Now, I don't have any "magic board". Any news about this?

 

[everBit]

Guys, it's very very strange that "magic" boards without definite reasons have failed.
Could you look what is error number?
And is there any voltage imbalance between cells?