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Battery Cell Deviation Question (.108 V)
510 3 2016-3-26
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madaerial
lvl.3
Flight distance : 512251 ft
United States
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I had a scary flight today. I've only been at this about a week, and today I forgot that although I have changed the units to imperial, RTH values are still entered in meters. So, I was trying to see how much battery life I could get out of my battery, so I figured I would fly until the low battery warning came on (I have it set at 20% - I generally don't fly too far away from "home"). Anyway, I was hanging out at 100 feet - not wanting to have to ascend to RTH height. I'm sure you can imagine my surprise when "Go Home" kicked on, and it climbed to 185 feet (according to the log, when I took off it was actually set at 100 m - 328 feet). I did drop it to 60 during the flight - again still thinking I was entering "feet" and not meters. Good thing I did, I think I would have pooped my pants if it had climbed to over 300 feet. Interestingly, in the log I can't find a message saying RTH altitude had changed, but once it was in "Go Home" flight mode it climbed to 181 feet (around 55 meters), and not the 328 feet noted as RTH altitude in the notes at takeoff.

Which brings me to my question - trying to understand what happened that flight has led me to my first log viewing and I noticed something more concerning than my inability to smoothly transistion meter to imperial (seriously though it would be nice if once I switched to imperial, EVERYTHING is in imperial) I noticed RED in my log. In the first ten seconds or so of flight, the log is recording battery cell deviation of .108 V. In general, the value is right around .01 - more or less. I'm assuming that much deviation is cause for some concern - as it is the only RED in the log. I'm pretty new to this..... can anyone tell me - should I be concerned? It really only happens from about 4.5 secs into the flight until about 7 seconds into the flight. Again, this is the first log I've ever looked at - so I really have no clue - but the red concerned me. Please! Tell me what you know!
2016-3-26
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madaerial
lvl.3
Flight distance : 512251 ft
United States
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Also, I think it's a little weird that with all the telemetry recorded, the log didn't list that I had changed the RTH altitude during the flight.
2016-3-26
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madaerial
lvl.3
Flight distance : 512251 ft
United States
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And in case anyone is wondering, with low battery warning set to 20%, I got a tad over 21 minutes flight time out of 80% of the battery. This is flying in P-GPS, with object avoidance on, shooting video and flying like ....normal.
2016-3-26
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madaerial
lvl.3
Flight distance : 512251 ft
United States
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I found this info in the P3 forum on a similar post:

Major deviation is when a cell differs more than 0.07v from the other cells.
Please note that normal batteries can have a few of these.
An abnormal battery will:
    A) Have most of the major deviations in one cell
    B) There will be multiple major deviations per minute, and more than 10 total
    C) The deviations continue longer than 1 minute
If your battery shows all symptoms (example, another) then this is considered a more severe case of an inefficient battery and may impact the battery life.
If your battery has only 1-4 instances on the same cell, don't worry too much about it. If it has 5-10 instances - then continue to track and make sure it does not degrade:

I guess I am going to have to continue to monitor the situation....
2016-3-28
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