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-Dji batteries-
959 16 2015-6-22
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daniel.frederik
lvl.3
Flight distance : 10656 ft
New Zealand
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The problem with most battery monitoring systems, in just about any application, is the use of the unloaded battery voltage as an indicator of remaining battery capacity: in my experience this is very misleading, load testing is the only indicater of a batteries condition ......but that requires more components & weight & development.  

I don't think our I1 batteries are suddenly discharging when in flight becuase of any problem but rather we took off having faith the remaining battery capacity was actually what was detailed in our Pilot apps.

Take a 5 year old car battery and compare the at rest voltage to that of a brand new one. There will be a small difference, perhaps 2-3 volts.  But then measure the actual current capacity of each battery and there will be a large difference.  Because Dji batteries appear to be gated we can't properly test them or charge with smart chargers, darn!

I think if we stick to basic rules of thumb this doesn't matter too much: mine are never store a charged battery ( 20-30% is fine so fly until you have to land ) and charge batterys a day at the most before use.

DF







2015-6-22
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jimhare
Captain
Flight distance : 239035 ft
Australia
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Interesting.  So are you suggesting that the issues some users are having, which include their Inspire dropping into the ocean, are more about the software initiating a forced landing based on inaccurate readings?

In other words, if the software just said "CRITICAL BATTERY WARNING - LAND NOW" but didn't force an immediate landing, there is a good chance the Inspire is still getting plenty of power and the pilot can just fly it in?
Or am I missing the point completely?
2015-6-22
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daniel.frederik
lvl.3
Flight distance : 10656 ft
New Zealand
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jimhare Posted at 2015-6-23 09:05
Interesting.  So are you suggesting that the issues some users are having, which include their Inspi ...

Hi Jim, I wouldn't go so far as to say that; I believe if your I1 has been in the air for a few minutes and a critical battery warning is given then it's a good assessment and it's time to think about landing.

The catch is if your battery has lain idle for sometime, it's capacity falls away but the voltage doesn't and your pilot app. suggests you've much more capacity than you really do and off you go with much less air time available to you than you think. It's only when the battery has been working for a short time ( under load ) that the two variables fall in line with one another.

Btw I didn't mean to suggest people have lost their birds despite having enough unrealized charge in their batteries to safely land with but I suspect I can account for why some people report a supposed rapid loss of battery power on some off their flights.  

But there has always been a misleading gap between a batteries capacity and it's resting voltage.
I used to carry a load tester, for my work, to accurately test batteries. it wasn't light and I'm glad there isn't one built in to our Inspire or the batteries.
Just fly with batteries charged no more than a day or two ago, store them at a level you landed with and this should be Ok. Or make a science of it!

For what it's worth I've had dozens of flights with my I1, one as far as a kilometer out to sea, and I haven't had any problems ...of any sort.  

And I'm sorry for the Gent whose I1 slipped into the San Francisco Harbor recently; every flight could end in disaster, it's no reason to hold back ( just don't fly over people! )

DF
2015-6-22
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jimhare
Captain
Flight distance : 239035 ft
Australia
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daniel.frederik Posted at 2015-6-23 13:01
Hi Jim, I wouldn't go so far as to say that; I believe if your I1 has been in the air for a few mi ...

Thanks for the clarification Daniel.   

Guess I still don't fully understand (and probably won't with any amount of instruction!)   so can't tell if you mean the drop is accurate or an issue with measuring it.

What I was referring to is the fact the that software initiates a forced landing immediately and if it would be better to just give a verbal warning and not take control, just in case you have enough power to get to safe ground.
2015-6-22
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daniel.frederik
lvl.3
Flight distance : 10656 ft
New Zealand
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Apologies, explanations aren't my strong point.  Maybe a verbal warning is a better idea; a last chance to tap into what little energy remains,  but I do believe the capacity readings are more accurate after we've been in the air for a few minutes and fit for their intended purpose of keeping people safe and our I1's intact   .....but some form of override does sound useful. There definitely is a drop in a batteries capacity over time which which isn't reflected in it's voltage so yeah, the catch is inadvertently flying to a point you can't return from!  I would happily conduct an experiment demonstrating this but alas these aren't ordinary batteries; they're gated somehow.
2015-6-22
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fullyestablishe
lvl.3

United Kingdom
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daniel.frederik Posted at 2015-6-23 13:47
Apologies, explanations aren't my strong point.  Maybe a verbal warning is a better idea; a last cha ...

Dear Daniel,

I believe that you make a valid point, I have been concerned how many people have left batteries several days into their auto-discharge process but have surprisingly high percentage battery remaining.

I also believe that part of the problem is that the critical battery function is based on the voltage of the lowest cell. I tested this last week by flying below 30% and keeping the voltage screen up and monitored each cell. On a TB47 the right hand cell was always the lowest but when I subjected it to transient load (maximum up command) it plunged some cells into the red and then around 11% it caused the right hand most cell to cross a threshold and I got the landing now and the percentage dropped to 3%. Thus I wonder if some of the sudden dropping has been after a heaver current draw was undertaken and the weakest cell dropped to its critical level. I certainly now fly with the voltage display option always on next to the battery percentage as this reports the lowest cell.
2015-6-22
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daniel.frederik
lvl.3
Flight distance : 10656 ft
New Zealand
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Hi fullyestablished, thanks for your observations and the tip of using the cell display for live monitoring of the battery.

I was reading one of your previous posts, is your Inspire1 flying well for you now? I hope so.

Df
2015-6-23
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GB44
Captain
Flight distance : 343848 ft
United Kingdom
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fullyestablishe Posted at 2015-6-23 15:34
Dear Daniel,

I believe that you make a valid point, I have been concerned how many people have le ...

Nice point about having the voltage displayed, but does this not mask what the camera is displaying in the main view.
2015-6-23
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w1der
Second Officer

Sweden
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jimhare Posted at 2015-6-23 13:08
Thanks for the clarification Daniel.   

Guess I still don't fully understand (and probably won't  ...

This is what I have been saying all the time ...

As long as the RC is connected to the bird ... pilot should be in control!

You never see a commercial flight do emergenzy landing with auto pilot engaged ...
2015-6-23
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jeremyconk
lvl.4

United States
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I have been following this battery issue, and thought it would never happen to me....

But yesterday it did..... I had (2) TB-48's both brick on me.... I flew them them 2 days before, landed them with 25 and 30%.... I had them in the case for 2 days and when I went to charge them One battery would not even light up or turn on, and the other had a strange one green light beep... Almost like an SOS...
When I plugged in the power to charge them.... NOTHING.... They would not even charge up....
I read somewhere on this forum how to "pop the top off", and disconnect the connector from the board to the battery.... I let them sit unconnected for 2 hours... Reconnected the plug internal plug, and both batteries came to life... I fully charged both of them, and they are working again.....
I believe that there is something goofy in the firmware...

I did not update to the most recent battery firmware update, because I read from April that if the user was having no issues, it wasn't necessary.... But I think it is, and I updated to the latest battery firmware this morning....

I really do feel like we are beta testers for this platform, and it is very frustrating that every time I use it, there seems to be a required trouble shooting session to get everything to work properly.....
That being said, the bird is solid, and I would never go back to a phantom..... But for 3K, I do expect a better user experience....
2015-6-23
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daniel.frederik
lvl.3
Flight distance : 10656 ft
New Zealand
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Yep, you're right. I'd still use the function to monitor my batteries performance occssionally .....or just leave it on and use a monitor to see what the drone is seeing.
2015-6-23
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houston
Second Officer
Flight distance : 5737940 ft
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United States
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So what is the critical low voltage that you should start thinking about landing ? Hope I am asking this correctly.
2015-6-23
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fullyestablishe
lvl.3

United Kingdom
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daniel.frederik Posted at 2015-6-23 19:24
Hi fullyestablished, thanks for your observations and the tip of using the cell display for live mon ...

Yes, mine is flying better now except for disconnects that can be unnerving. One should alway be aware that altitude hold is relatively weak in even moderate winds.
2015-6-24
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fullyestablishe
lvl.3

United Kingdom
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GB44 Posted at 2015-6-23 20:09
Nice point about having the voltage displayed, but does this not mask what the camera is displayin ...

Having all the cell voltages does cover the whole display so I only do it to better understand cell behaviour. The display voltage option just puts the voltage under the battery percentage.
2015-6-24
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FictitiousPerso
Second Officer

United Kingdom
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jimhare Posted at 2015-6-23 13:08
Thanks for the clarification Daniel.   

Guess I still don't fully understand (and probably won't  ...




I'd like to be able to take control regardless of battery state as I'd rather kill a battery than killing the inspire, safe a smart battery or kill your inspire?


I think we all know the answer for that one !
2015-6-24
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fullyestablishe
lvl.3

United Kingdom
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FictitiousPerso Posted at 2015-6-24 16:25
I'd like to be able to take control regardless of battery state as I'd rather kill a battery th ...

That is so true and it is well established in aviation. One can easily do $1m of damage to an aircraft turbine by over torquing, and thus one has to be so careful in setting power levels, even on the takeoff roll if one sets max allowable torque on start of the roll it will exceed it by the time you are half way down the runway. However, in an emergency all pilots will bury the throttle in the firewall, as you say, it is better than the alternative. To shut off rotors whilst there is still enough energy to being it down safely is just silly.
2015-6-24
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fullyestablishe
lvl.3

United Kingdom
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houston Posted at 2015-6-24 07:19
So what is the critical low voltage that you should start thinking about landing ? Hope I am asking  ...

That is a good question and one that the battery percentage is trying to answer for you. I think it starts to get more freaky when your cells will no longer balance and I wish I knew what an acceptable imbalance was. With a balanced battery, fully charged before a flight I would still aim to be close to landing at 30% but I need to note down what seem to be the voltages that cause a cell to go yellow, red and what will cause the craft to land and what causes an immediate shutdown.
2015-6-24
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