Hi all,

I have a F450 sized quad powered by a Pixhawk v1. I am using a 5000Mah 3s battery.

When I arm the quad and start flying it always goes into battery failsafe mode at approx 1 minute of flying.
It was suggested to me to try and diagnose the issue by viewing the log files.

I have downloaded the log file from my flight today but am unsure what I am looking for.

Was wondering if anyone could please analyze my attached log file and help me determine what is causing the quad to always go into battery failsafe.

Attached is the .bin & .log files from today's flight.

This is the LogAnalyer file from Mission Planner

Log File C:\Users\Jason\Desktop\MissionPlanner-latest\logs\QUADROTOR\1\2017-04-14 11-07-56.log
Size (kb) 8959.1279296875
No of lines 108205
Duration 0:05:48
Vehicletype ArduCopter
Firmware Version V3.4.6
Firmware Hash e707341b
Hardware Type
Free Mem 0
Skipped Lines 0
Test: Autotune = NA -
Test: Brownout = GOOD -
Test: Compass = GOOD - mag_field interference within limits (14.15%)
Max mag field length (612.36) > recommended (550.00)

Test: Dupe Log Data = GOOD -
Test: Empty = GOOD -
Test: Event/Failsafe = FAIL - ERRs found: FLT_MODE FS_BATT
Test: GPS = GOOD -
Test: IMU Mismatch = FAIL - Check vibration or accelerometer calibration. (Mismatch: 3.23, WARN: 0.75, FAIL: 1.50)
Test: Motor Balance = WARN - Motor channel averages = [1479, 1552, 1530, 1562]
Average motor output = 1530
Difference between min and max motor averages = 83
Test: Parameters = GOOD -
Test: PM = NA -
Test: Pitch/Roll = NA -
Test: Thrust = NA -
Test: VCC = GOOD -


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What voltage is your FS set at?  Looks like it drops to 11.5 pretty fast, and then you hit failsafe, then slowly drops from there. You could set it at a lower value, or check a new battery

Thanks for the reply @Mossbackfarm. My battery failsafe is set at:

Low Battery 11.5

Reserved MAH: 300

In Mission Planner whilst diagnosing the issue I have the battery failsafe disabled.

So you think it could be just a dud battery?

The battery failsafe is correct.  The battery was charged to 12.5 volts and when you took off the battery voltage dropped to 11.5.  This unit draws a lot of power and this causes the battery voltage to sage.

You should have your failsafe set to 10.5 volts as you don't want the battery to fall below 9 volts or 3 volts per cell.  It looks like you continued to fly after the failsafe for about 5 minutes at which time the battery was at 10.5 volts.

With my 450 unit and a 5200 battery I get about 10 to 15 minutes of flight.  I only draw about 20 amps where yours is about 30 amps.  Your unit must be a little heaver than mine.  Motors are not maxed out and look good.

With some old 5100 batteries that have been used for 400 plus flights I can get about 6 minutes of flight time and then I have to land soon.  I have since retired those batteries since the internal resistance has become a problem.

Thank you Michael for your feedback. I thought it may be the battery.

I am going to have a play with the drone today and see if I can make it a bit lighter. It is a 450 sized drone that I purchased of Ebay.

Uses 30A Simonk ESC with 2212 920KV motors

5000Mah 3S battery

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