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SEVERE Battery failure at 57%
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4000 53 2015-5-6
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matty
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This may be considered a battery bug or an inspire bug.

I flew with batteries registering at 65%+. I believe they had partially self-discharged, but they still read 65% or more.
When the battery button was pressed they registered three solid green LEDs before TKOF.

Part way through the flight  (1.5 minutes) and when they were about 55 or 57% the battery level immediately dropped to 5% or 7%

This problem was repeated 3 times in a row, each with almost identical battery states at the start.

Now before you go and tell me I MUST only use batteries that start at 100% and have just come off charge, I will remind you that these batteries flew for about 1.5 minutes normally, and at the start registered THREE GREEN LEDs. Each battery has been used 10+ times, and there was no warnings on screen before the flight to tell me to recharge the battery.

Parts of these three log replays have been sped up 4x so you don't have to sit through most of the flight. minutes

For a couple of these flights I was testing the new Renaat ND filters and tracking traffic as it crossed the bridge. You can see the cammera panning left and right.
In my opinion, we would call this a battery monitor/LED bug where the battery state before the flight really should have been ONE blinking green.It would also ne great if the firmware informed the user that, "This battery has self discharged in the last XX days" etc etc









2015-5-6
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PeteGould
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This is consistent with my growing suspicions concerning Inspires that suddenly drop out of the sky.

I would certainly call it a bug.  Likely it is related to an insufficient algorithm in the battery's logic, which may rely too much on the battery's voltage as it sits on the shelf.  Unfortunately the voltage of a battery with no load does not accurately predict what will happen when you put a load on it - thus the sudden change when the system recalculates.

So I would say this demonstrates WHY you have to initiate a flight only with a fully-charged battery: because that is the only situation in which the remaining-charge indication is likely to be accurate.  Certainly it's a bug or limitation but in the meantime the safety of our equipment and anything in its path depends on our recognizing it.
2015-5-6
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Rockeyes
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There you go just as we suspected. Well done matty for posting that up and for getting the Bird back safe. I think DJI should issue a formal notice to ensure all users operate with a fully charged battery before any flight whilst a solution is sourced.
2015-5-6
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Fred D
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Since I stopped flying on partially charges batteries I have not had this rapid discharge problem again. I will now ONLY fly on fully charged batteries
2015-5-6
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Rbimd
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The battery controller chip which coordinates the charging/protection/self-discharge and reports the state of charge as a percentage, MAY BE inaccurate after a self discharge, and be at least partially responsible for this phenomenon (see my other post Understanding battery "sudden-drop " phenomenon). Until DJI addresses this issue, the common recommendation is to only fly using recently and fully-charged batteries. I am collecting data on this issue and if you are able to record the detailed battery status screen information before and immediately after one of these events, it will be very useful information for all of us.
2015-5-6
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sbarryjackson
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I have you tell you, you have balls. Testing by a river, heavy woods, next to a bridge. I salute you sir.
2015-5-6
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arunmehta
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Rbimd Posted at 2015-5-6 20:52
The battery controller chip which coordinates the charging/protection/self-discharge and reports the ...

The corollary to your assumption means that we cannot ALSO rely on the "chip" telling us accurately that the battery is indeed 100% charged. If the chip is faulty maybe the 100% is only 70% ..??
2015-5-6
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dmytchak
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Matty,

Thank you very much for taking the time to post this.   It's one thing reading about the anomaly on the forums but watching it made me cringe.  

Very happy you were able to safely land your aircraft.   

I will now fly with only freshly charged batteries also.  You may have just saved my Bird!!!

Many thanks!
2015-5-6
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JKT
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The new firware should be able to fix that problem!
2015-5-6
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FictitiousPerso
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Great post, well spotted
Basically our smart battery's are stupid !
Niceeeeee!
2015-5-6
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markjacobs.talk
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arunmehta Posted at 2015-5-6 22:02
The corollary to your assumption means that we cannot ALSO rely on the "chip" telling us accuratel ...

No - this is why calibration of the batteries is so important.

The packs/firmware must be periodically 'told' what is zero (reference point) and what is 100% (reference point) by cycling them down to LVC of the pack.
ALL packs lose capacity with age/internal resistance increasing and the calibration keeps the reference correct for a particular age/state of pack.   
2015-5-6
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Rockeyes
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JKT Posted at 2015-5-6 22:31
The new firware should be able to fix that problem!

Great but based on what? I don't see that on the update list or DJI putting out some notice they even recognise a problem.

2015-5-6
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PeteGould
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markjacobs.talk Posted at 2015-5-6 22:39
The packs/firmware must be periodically 'told' what is zero (reference point) and what is 100% (reference point) by cycling them down to LVC of the pack.

EXACTLY.  And this is why Bob Marley's advice to ignore the whole issue was so dangerous (and in turn why he was banned).

But beyond the periodic full-cycle charge, I also think you CANNOT trust the "remaining charge" indication unless you started out with the battery at 100%.  Once the pack is under load (which it won't be until the motors are spinning and bearing the weight of the Inspire), the system will recalculate an ACTUAL remaining charge a few minutes into the flight, with potentially disastrous results.
2015-5-6
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PeteGould
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arunmehta Posted at 2015-5-6 22:02
The corollary to your assumption means that we cannot ALSO rely on the "chip" telling us accuratel ...

Theoretically true, though in practice it doesn't seem to be where the problem is.
2015-5-6
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w1der
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I don't recall this was ever reported before the latest update ... However alot of reports after this firmware upgrade ...
Hopefully they will get it fixed for the next update!
2015-5-6
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stevenstringer
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This happened to me as well!  It was the first flight after the latest firmware update, the battery was at about 60%, I used it to charge my controller as it had been sitting fully charged for a few days.
2015-5-6
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w1der
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Oh ... New update today ... Just completed it ... And noticed that my second battery also was updated when I put it in the I1 after the main update.
I will be doing a new fully discharge and fully charge of my battery before starting to use them after the update as this is adviced in the (new) pilot app again ... Just to be sure
2015-5-6
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RichJ53
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You need to try the new firmware and retest your batteries. I would like to know if they fixed it!!

Rich
2015-5-6
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matty
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RichJ53 Posted at 2015-5-7 09:36
You need to try the new firmware and retest your batteries. I would like to know if they fixed it!!
...

I'll put two batteries aside and let them discharge for 10 days, then see what the status light says.

2015-5-6
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DJI-Autumn
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Matty, about the battery problem, without going through the whole threads, let me do a clarification first.
When battery level  down to 7%, it will re-estimate the SOC and the estimation would be more accurate.
After about 20 charge/discharge cycles, the estimation would be less accurate and might cause the sudden drop. That's why we ask customers to charge and discharge completely once after 20 charge/discharge circles (and before the first time you use it).
I assume that you've used it for about 20 times (you said 10+), that's why the SOC estimation can be such inaccurate. Battery has more to do with that, not Inspire 1 itself.

2015-5-6
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matty
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DJI-Autumn Posted at 2015-5-7 12:12
Matty, about the battery problem, without going through the whole threads, let me do a clarification ...

One battery had 7 cycles, one had 10 cycles, and one had 11 cycles.
I usually fly batteries down to about 30%, then charge before I use them next,
But on this occasion I had all 9 of my batteries fully charged for many days.
I pressed the button to see if I had three or more green lights, and I did, then I simply flew, assuming the green battery lights were accurate, and they are not.
I'm not sure what SOC refers to. (System on chip?)
2015-5-7
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GENETTICO
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matty@psionic.c Posted at 2015-5-7 21:26
One battery had 7 cycles, one had 10 cycles, and one had 11 cycles.
I usually fly batteries down  ...

I agree with Pete's theory there would have to be some tests done to confirm this, however with my current understanding of the battery, his explanation makes the most sense to me. just IMO!
2015-5-7
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mountmotor
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matty@psionic.c Posted at 2015-5-7 21:26
One battery had 7 cycles, one had 10 cycles, and one had 11 cycles.
I usually fly batteries down  ...

If the LED lights were not accurate then what did the app tell you?
2015-5-7
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Rockeyes
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PeteGould Posted at 2015-5-6 23:56
EXACTLY.  And this is why Bob Marley's advice to ignore the whole issue was so dangerous (and in tu ...

That's also how I'm seeing this.

How about this? The Inspire sees a partially charged battery in the rested state and calculates the flight times. After a short period of flight it recalculates and sees the true voltage remaining, based on the voltage comparison between the two and the short time flown it miscalculates the true remaining power available.

Or The batteries have put themselves into discharge mode as part of their storage programing. The operator then goes to use the battery seeing there is usable power remaining. However when used the battery does not come out of self discharge. The question then is what stops the self discharge? I would have a guess at on of two things. The first being its reached it min voltage level as designed OR it is placed on charge.

Yes we should follow the manufactures instructions with our eyes open and to be safe ensure batteries are fully charged before flight.
2015-5-7
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DJI-Autumn
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matty@psionic.c Posted at 2015-5-7 21:26
One battery had 7 cycles, one had 10 cycles, and one had 11 cycles.
I usually fly batteries down  ...

State-of-Charge.
Did you discharge the battery to 5% or lower then fully charged before its first flight? That's very important. I'll check if we highlight it in the manual..
2015-5-7
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RichJ53
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DJI-Autumn Posted at 2015-5-8 09:34
State-of-Charge.
Did you discharge the battery to 5% or lower then fully charged before its fi ...

Can I ask why these LiPo batteries require discharging to 5%? This is not a normal situation for LiPo batteries in the industry. They do not develop memory like other battery chemistries and seems strange to me.
Thanks
Rich
2015-5-7
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DJI-Autumn
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RichJ53 Posted at 2015-5-8 09:40
Can I ask why these LiPo batteries require discharging to 5%? This is not a normal situation for L ...

I guess it's related to SOC estimation.
Pls refer to what I mentioned above "When battery level  down to 7%, it will re-estimate the SOC and the estimation would be more accurate." .
I do not know too much about the battery industry, that is what I summed up after discussion with other colleagues. We can discuss about it.
2015-5-7
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RichJ53
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DJI-Autumn Posted at 2015-5-8 09:47
I guess it's related to SOC estimation.
Pls refer to what I mentioned above "When battery level  d ...

Thank you for answering Autumn,

So if I understand you, its to do with the intelligent battery electronics (software) that monitors the battery life (run time). When the battery is run down to 5% then this resets the electronics for accuracy?
I guess this makes sense, but it would be nice to find a better way to refresh the battery monitoring electronics.

Rich
2015-5-7
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PeteGould
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RichJ53 Posted at 2015-5-8 09:40
Can I ask why these LiPo batteries require discharging to 5%? This is not a normal situation for L ...

I think this has been covered before but it's worth mentioning it again here.  The "remaining battery charge" indication supplied for display on your mobile device is not total lipo cell capacity.  It is the remaining percentage of what DJI considers acceptable remaining charge.  So when the display says "5%" that's 5% of remaining charge before the logic in the intelligent flight battery tells it to turn off, which is actually more than the actual remaining battery capacity.  In sum: 5% on the DJI display is significantly more than 5% in reality.  So you won't harm the lipo cells by discharging to this amount, or until the battery shuts off.  It's designed not to take you into critical lipo territory.
2015-5-7
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RichJ53
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PeteGould Posted at 2015-5-8 11:34
I think this has been covered before but it's worth mentioning it again here.  The "remaining batt ...

Thanks Pete, that's nice to know. It just goes against your normal battery logic...
2015-5-7
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PeteGould
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RichJ53 Posted at 2015-5-8 11:38
Thanks Pete, that's nice to know. It just goes against your normal battery logic...

Agreed.  This is the "intelligent" part of the intelligent flight battery, which is intended to save novices from themselves.  The theory is that by inserting a microprocessor between the battery and the user, there is less chance of the battery being harmed by either being left fully charged long-term or by being run all the way down to 0v.  The only problem is that they don't explain it anywhere so unless it comes up in discussion, nobody knows.
2015-5-8
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matty
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mountmotor Posted at 2015-5-8 03:24
If the LED lights were not accurate then what did the app tell you?

Did you watch the video I posted?
2015-5-8
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matty
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double post
2015-5-8
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RichJ53
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matty@psionic.c Posted at 2015-5-7 09:57
I'll put two batteries aside and let them discharge for 10 days, then see what the status light sa ...

Have you updated your Inspire with the latest firmware? It would be nice to see these batteries now with this last fix. You shouldn't need to wait 10 days.... update the batteries and give it a try.

Rich
2015-5-8
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kirk.pleasant
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Hi I posted this about 1 month ago

http://forum.dji.com/forum.php?mod=viewthread&tid=12015

I have had the same issue. It was caused by a bad cell in a TB48.
I have a second TB 48 now that is also having a cell that is dropping voltage.

I now have 2 bad batteries and I live in a country without a DJI dealer. Also the main airline that serves my country has now put a limit of 100W for lipo batteries so I am unable to take them back to the dealer I bought them from for a replacement... DJI batteries SUCK!
2015-5-9
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kirk.pleasant
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DJI-Autumn Posted at 2015-5-8 09:34
State-of-Charge.
Did you discharge the battery to 5% or lower then fully charged before its fi ...

Hi DJ -Autumn,

There is a  definite issue with the DJI NOT SO Smart Batteries.
I now have 2 TB48 that are paperweights and no way to replace them since there is no DJI dealer in the country that I live and the airline I fly for has now put a restriction of 100W lipo batteries carried on board.
Can you please advise what can be done?
Please see my previous post.

http://forum.dji.com/forum.php?mod=viewthread&tid=12015

Thank you
2015-5-9
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matty
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RichJ53 Posted at 2015-5-9 11:07
Have you updated your Inspire with the latest firmware? It would be nice to see these batteries no ...

Yes. I have updated them and they are sitting dormant. In an ammo tin!
2015-5-9
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matty
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RichJ53 Posted at 2015-5-9 11:07
Have you updated your Inspire with the latest firmware? It would be nice to see these batteries no ...

Yes. I have updated them and they are sitting dormant. In an ammo tin!
2015-5-9
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RichJ53
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kirk.pleasant Posted at 2015-5-9 16:30
Hi DJ -Autumn,

There is a  definite issue with the DJI NOT SO Smart Batteries.

Sorry to here you are having issues and DJI should find a way to help you out (maybe send them back to China for replacement).
Matty, I watched your video and it is disappointing that your battery life seemed to vanish. Did you take a screen shot showing the battery cells? Because kirk is right, if one bad cell is the cause, your total battery voltage will drop suddenly setting off the same result in your video.
2015-5-9
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matty
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RichJ53 Posted at 2015-5-9 23:29
Sorry to here you are having issues and DJI should find a way to help you out (maybe send them bac ...

Hi Rich,
All battery cells were even and fine on all three batteries. I checked immediately after he failure as I thought I had a bad cell. I didn't screen shot the battery page of the app at the time, sorry.
They later took a 100% charge and flew for the full expected endurance.
The problem is clearly these two things revolving around self discharge:
1) that the three green LEDs on the battery after a self discharge do not accurately reflect the actual charge in the battery
2) when a self discharged battery is used it initially reports a 60-67% charge, and flies based on that for about 1.5 minutes before zipping down to 5-7%
2015-5-10
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