Power Module burn out - Fatal Crash

Been using Navio2 for some time now and drones for about 9 years.
Have just build a new quad-copter with 6S configuration based on the Tarot X4 frame.
However, whilst doing basic tuning / test flying I’ve suddenly encountered burn out of power module resulting in fatal crash. (drone,…no one got hurt)
I happen to be an electrician and service technician with many years experience. Right at the time of purchase was slightly bewildert that there are no precise specs for power module. Usually with electronics there is some examples as to how long an excess current can be tolerated and for how long. (I.e. 20% excess current = damage after 4 seconds)
From previous flights I know current was around 60A with peaks of around 90A.
In this last flight had to accelerate suddenly which obviously pushed it over the limit.
I’ve just seen Marc Lebret previous mentioning the higher voltage to the Navio board when X90 plugs are used to achieve higher current sensing. But why would Emlid even mention this on the sales page if that may cause problems to the Navio board ?

Also noticed some previous options mentioned as a possible alternative, but some of those items/ links are no longer available.
So, what is the official solution if currents of up to 200Ah peak / 60 Ah average are expected?


Update 3.7.21

For those who don’t want to read following report,……in a nutshell: Check your power module for poor soldering joint and especially the negative link (black) and it’s solder thickness.

I found the whole incident weird and initially couldn’t retrieve the .bin file as was corrupt due to sudden loss of power.

I then went to inspect the PM closer and found that in fact the positive connection (red) and the related components appear to be fine, yet the cable to the Navio2 was burnt out (insulation burnt off). But closer inspection revealed only the two GND wires appear to be affected.

Then I’ve discovered that the PCB track for the negative wire had in fact burnt out which in turn caused some excess current to flow via the GND wires and hence those burnt out.

I’ve been working with electronics for decades and seen information relating to PCB’s and high current applications where it is recommended to have at least 2.5mm of solder on those tracks to support the high current or in some cases a small copper wire is soldered onto the track for the same benefit. - Yet no such thing on my PM !

(Have attached a photo of a commercial electronic board where the tracks are much wider and many solder dots have been applied to support higher current (Navio cable shown for size comparison) – Yet that particular board is only expect to carry about 1/10 of the current that the Navio PM supposed to handle)

Finally managed to access .bin file and as everyone can see the total current came only close to 100A very briefly at the start of the flight but then stayed well below the rated 90A . - Yet still burnt out due to a weak PCB track.

The spike at the end was obviously created by PM and cables burning out and the subsequent shutdown of FC.

I would like to fix (simply solder negative connection) and test my PM. - Just to see if in fact still operational, not for actual use in drone due to safety reasons.
However, as the connection cable is not available as a spare part may not be able to fully operate / test it again. :frowning_face:

But having said that I will try the “Mauch” 200A PM instead as suggested by Marc Lebret.

So, check your soldering joints and PM.
…and then, happy, safe flying.

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Hi Karl,

Sorry to hear that you faced such an issue. However, thank you for describing your investigation. I believe it might be useful for many users.

I wish I can help you with the power module cables. However, we indeed don’t provide spare parts because all of them are used for power modules production. If I can be of any other help, please let me know.

Hi Svetlana,

I have been able to do testing on the PM despite not having a new cable.
My suspicion has been correct and PM appears to be working fine and in fact it was all caused by that weak negative track burning out. Shame having had such a “weak link” in the system.
…needless to say won’t be using that PM any-more on any drone of mine.

Hi Karl,

The Navio2 power module has its limitations as an electronic device. As far as I got, it burned out since the current sensing limit was exceeded. Probably, your hardware setup indeed requires a power module with a higher max current sensing value.

From our side, we’ll think about how to deliver such limitations to users better.

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