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What is the significance of battery voltage colors?
702 11 2016-1-18
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johnsr
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While flying in relatively cold weather (-1°C) I noticed that the battery voltage values changed color during the flight before I came to the 30% low level warning (toggle set to show them on the screen). Can someone explain the significance of the orange or red values? The battery level was above 40%, so these do not correspond to the level values. They seem to correspond to load levels; but I am not at all sure. I assume if we see red voltages, one should let off the sticks, but I am fairly light on those anyway. Thanks in advance for an explanation (or a link to one).

2016-1-18
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hummingbird.uav
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The colors are voltage related.  Drawing lots of current from the battery will cause the voltage to decrease.  Temperature of the battery also affects how it responds.  See this message link for my video on this subject.
http://forum.dji.com/forum.php?m ... 0&fromuid=47441
2016-1-18
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johnsr
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hummingbird.uav Posted at 2016-1-18 19:10
The colors are voltage related.  Drawing lots of current from the battery will cause the voltage to  ...

Thanks, your battery post was interesting. I had previously not focused on the cell colors, until flying in the cold; after looking at your video again, and unless I am mistaken, it would appear that cell voltage above 3.60 volts is shown in "green", less than 3.60 volts but greater than 3.50 volts the value is given in "orange", and 3.50 volts or lower its shown in "red". The surges of power came as I was heading upwind.

Incidentally it took about 2 minutes of stationary flight at take-off to get the battery up to 20° C. It would be useful to have the battery temperature appear somewhere on the screen when its below 20°C. (I know that one can bring up the whole battery menu)
2016-1-18
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hummingbird.uav
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johnsr Posted at 2016-1-18 11:55
Thanks, your battery post was interesting. I had previously not focused on the cell colors, until  ...

I have submitted a request for a temperature indication on the main screen.
If your battery was below 20°C and flying I assume it was "Full" charged as a partially charged battery voltage most likely would have sagged to 3.5 volts and caused an autoland.
2016-1-18
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johnsr
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Yes, the battery temperature display, at least when its below a safe level, would be an improvement . As for the flight: I always start with newly charged batteries. I was doing cold weather test runs at low altitude in open fields, before planning some filming in winter conditions.
Thanks and good flying!
2016-1-18
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ant.1141
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i had this problem when flying the other day. i had a warning saying (propultion outlet limited to ensure the safety of the batter) i had no idea what it was untill i found out it was due to low temp on the battery. i now warm the battery up by just hovering for about 2 min and see the battery temp too about 20. if not then the phantom could auto land because the vaultage will get to low. the new firmware will protect this and restrict propultion like i said but best to warm it up before flight and then the voltage will be fine l.
2016-1-18
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hummingbird.uav
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I suggest you look at the battery temp after landing.  I have seen it in the 50s.
2016-1-18
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johnsr
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hummingbird.uav Posted at 2016-1-18 20:30
I have submitted a request for a temperature indication on the main screen.
If your battery was be ...

Just for information and as a compliment to your helpful video, here is a battery curve taken in-flight in moderately cold conditions (2.5°C) with a freshly charged battery at 20°C. As one can see in these "ideal conditions" the initial drop is not big. Also there is the characteristic "recovery" when the load is removed (motors stopped) at the end of the flight. Unfortunately I couldn't note the battery temperatures after take-off.

P3P in-flight battery curve

P3P in-flight battery curve

2016-1-19
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dji-p3p1
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johnsr Posted at 2016-1-19 17:41
Just for information and as a compliment to your helpful video, here is a battery curve taken in-f ...

Wow. That's fantastic info. How did you get the data to plot the curves.

I'd like to do it for each individual cell and see which one is dying first.  
2016-1-19
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hummingbird.uav
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johnsr Posted at 2016-1-19 17:41
Just for information and as a compliment to your helpful video, here is a battery curve taken in-f ...

Nice graph.  Taking the single cell voltage sag and multiplying by 4 would give a battery sag of ~1.2volts.  This is a bit less but close to the cold bat voltage sag I have measured.  I added a graph to my video message.  How were you able to capture the data for your graph?
2016-1-19
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johnsr
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hummingbird.uav Posted at 2016-1-19 16:06
Nice graph.  Taking the single cell voltage sag and multiplying by 4 would give a battery sag of ~ ...

Sorry no tricks, did it the old way... note pad, then to Excel. Checked during a flight this afternoon that (as expected) there is some small dispersion in cell values (see screen shot below taken as P3P returns; air temp 1°C.). The DJI guys are correctly showing you the lowest cell voltage. Wind calm today so I didn't see any surges.

Screenshot_20160119-151929.jpg

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hummingbird.uav
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johnsr Posted at 2016-1-19 23:43
Sorry no tricks, did it the old way... note pad, then to Excel. Checked during a flight this aftern ...

I have a way of transmitting the iPad screen output wirelessly to a laptop where it's recorded.  Then I transcribe the data values to excel while watching the video.  Slow but accurate.
2016-1-19
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