Bad Battery Symptoms

[MavicFT1P]

Can someone please elaborate on the symptoms of a Bad battery.

I got a critical 3.50 undervolt yesterday which initiated a landing.

The strangething was that leading up to it the Aircraft slowed (even with %50 capacity) down leading up to it
as if it were running on NiMH or old NiCD batteries.

Weather outside was mild at low altitude, so temperature wasn't a factor.

Has anyone experienced slowage, or critical undervoltage at above %30 capacity.
It's a Mavic Pro

 

[lolo780]

Post a flight log. The M2 goes into auto landing easier than the M1.

What was your battery temp?

 

[MavicFT1P]

let me check the screen recording, 2 secs

 

[MavicFT1P]

i closed screen recording when i was troubleshooting it mid flight it seems >_<A

Ambient temp was 20. Battery takeoff temp was 27.

It's here i should mention the battery gets run down to near critical, one light very often.
But it has always charged up fine no LED errors, low performance

If the Undervolt happened out of the blue, i could accept it as bad battery, replace, fixed.

But the way it slowed down (for 5-10 mins) beforehand was strange. i thought it was the wind, as you do, but it was slowly
losing peak power which should have caused an undervolt straight away?

 

[RayOZ]

If you have AirData subscription, I would recommend uploading you flight logs there. They have a battery tab and you can view trends and see if there's any major cell voltage deviation. I do have a habit of uploading my flight logs to AirData after a flight session, then review the batteries to see if there's any issues.

 

[MavicFT1P]

I don't subscribe unfortunately.
I'll find my flight log and post
thanks

 

[old man mavic]

the fact that you run the battery down to a low level often could be a contributing factor,it only needs one cell to be out of sync with the others you should let the battery cool right down before you charge it again but if you are not flying for a few days then leaving it at 25 per cent is not a good idea you would be better off landing at 40 per cent you will still get a good flight time in you could try the deep discharge to around 8 per cent as described in the manual this is supposed to reset the balance circuit in the battery then do a full recharge and see what your individual cell readings are at you do not say how many charges the battery has had or how you have been storing them

 

[MavicFT1P]

the fact that you run the battery down to a low level often could be a contributing factor,it only needs one cell to be out of sync with the others you should let the battery cool right down before you charge it again but if you are not flying for a few days then leaving it at 25 per cent is not a good idea you would be better off landing at 40 per cent you will still get a good flight time in you could try the deep discharge to around 8 per cent as described in the manual this is supposed to reset the balance circuit in the battery then do a full recharge and see what your individual cell readings are at you do not say how many charges the battery has had or how you have been storing them

The battery is relatively new, only about 15, maybe 20 charges.
I always check cell's before flight, voltage on the main screen, etc.

I Never recharge hot battery's after flights. I do charge and them at %100
so they always ready to go,
but if it's been more than 2-3 days I will
bring them down to %95 and charge before flight.

Theres a link to this thread in another which might explain away some of the strange behaviour.

Alientech, Titan, Nanosync, 4HAWKs. Which for 2019?

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Thanks for the help advice though

 

[AnzacJack]

Are you saying that the aircraft was flying slower when under 50%. This seems strange and not normal behaviour that I have ever heard of.
Would be very interested in seeing your logs interpreted by the pros here

 

[MavicFT1P]

Are you saying that the aircraft was flying slower when under 50%. This seems strange and not normal behaviour that I have ever heard of.
Would be very interested in seeing your logs interpreted by the pros here

Yep, not just slower but slowing. NimH RC Battery running out is best I can Explain it.
Never seen anything like it with Mavic, or Li-Po.

 

[WithTheBirds]

the fact that you run the battery down to a low level often could be a contributing factor,it only needs one cell to be out of sync with the others you should let the battery cool right down before you charge it again but if you are not flying for a few days then leaving it at 25 per cent is not a good idea you would be better off landing at 40 per cent you will still get a good flight time in you could try the deep discharge to around 8 per cent as described in the manual this is supposed to reset the balance circuit in the battery then do a full recharge and see what your individual cell readings are at you do not say how many charges the battery has had or how you have been storing them

Deep discharge does not reset any “balance circuit”. It might be of some benefit to a pack severely out of balance (allowing longer for the bleed resistors to operate) however the success has been very limited in this regard and any benefits short lived. Poor cell balance is a symptom of increased internal resistance- an irreversible condition.

The best you can hope a deep discharge might realise is increased accuracy of the coulomb counting algorithm however this is only part of the fuel gauging scheme. It is no longer recommended by DJI and unnecessary for any monitoring scheme incorporating impedance tracking and other advanced management.

 

[MavicFT1P]

Just for the record, the battery is in the lipo bin out the back and new one ordered.
So dont want to drag this out. BUt the battery boogeyman is kind of here now, so more help/info is good

In Assistant I use Non-DJi battery and 3.5 v critical (aka landing like it or not)

My vel & acc parameters can be as high as 8 sometimes.
I always gotten GO "max rpm" and Battery draw/error warnings with these settings pinning it, but
this has happened for a long time, with other batteries too, so dont think is the issue.

I mentioned the battery is new(er) than my others