P3A Erratic behavior with 40% battery

Joined
Jul 8, 2016
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#1
Yesterday I try to fly P3 A with about 40% battery, good weather no winds. The Phantom took off OK from a parking roof top and within couple of minutes at about 50 ft away and 15 ft up, it became wobbly and drifting few feet randomly and quickly. The warning on remote was something like ..."Battery critically low. Aircraft will land now". " Calibration error".. something like it.
I managed to land it safely and took it to another location around 20 miles away and encountered the same problem. I swapped the battery with a fully charged one and flew at least 15 minutes without any issues.
I didn't have a chance to fly it again with the same battery that gave me the problem.
Did anyone experienced the same problem? Is it battery related?
 
Joined
Jul 8, 2016
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#3
40% is not really low, right? I will check the battery voltage when I go home. So If one cell is bad, is the whole batt is a toast?
Thanks!
 
Joined
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#4
anytime you are accelerating or climbing, you can cause a temporary (or even actual) voltage drop due to the increased current draw. So once you start getting close to the critical voltages where auto return or landing come into play, you can drop below that level pretty quickly. Common response around here "ALWAYS start with a fully charged battery" to avoid just the type of situation that you experienced.
 
Joined
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#6
40% is not really low, right? I will check the battery voltage when I go home. So If one cell is bad, is the whole batt is a toast?
Thanks!
If one cell is bad then yes, it's shot, I wouldn't take any chances with it.. Some ppl will try to slow charge at like .1 amp to try and recover the cell, but my experiance with using lipos is once the cell goes bad, it's never the same.. Also when one cell goes bad, it will drag all the other cells down with it very quickly .. If the cell ends up being bad, then most likely that's what caused it to go from 40% to 8% critical battery and "autoland" so quickly ... If the cells are all good ( I would check using the app, also I would hold the quad in your hand, and throttle up slowly and watch each cell, if all 4 cells go down pretty evenly under load then you know they are all good, if one cell jumps out at you and drops considerably lower than the rest then boom, you got your answer) otherwise I would say it's just a compass issue, and to recalibrate your compass again making sure you do it right, and with nothing metal or electromagnetic around. It also prolly wouldn't hurt to do an IMU calibration if you have never done one... You can check the calibration by clicking on "check IMU" under advanced settings in the app.

Hope this helps

Edit: also, the fact that low batt warning goes off at 30% on default, I would say 40% batt power is not the best way to START a new flight .. Just my opinion.


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