Battery Life DJI NASA vs Arducopter

Hi All,

Great forum very useful information and some dedicated guys on here.

I have a question, I have two hexacopters, both DJI F550 frames with stock motors and ESCs.

Initially I was impressed with the out of the box performance of the NAZA controller and found it to be a great starter platform to learn to fly but as with everything it was not enough for me and I decided to go Arducopter to experience the added benefits such as programability and waypoints. Rather than massacre the first copter I decided to build a new one.

Two fully functional copters has allowed me to do some comparison the most significant difference is battery life right now with a 3S 5500mAh battery I get 4 minutes flight time from the Ardu based copter and an astonishing 13 minutes from the NAZA based craft.

I'm using telemetry to monitor performance and determine when to come in to land. At the end of the short flight the motors are quite hot. Batteries are drained when connected to the charger. Current draw is always 90A see plots!

Did anyone else experience this? With such short flight times I am going to have to think about taking on a DJI Wookong M ... but having spent so much time with the Ardu I'm giving it one last chance! I know that the platform has so much more to offer!

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Replies

  • Hi, that is a good experiment but the only thing that can tell you how much charge is left on the batteries is a quality voltmeter (after landing) or one of the better ones of the battery checkers you find on the RC market. After some experimentation you will know what to make of the onboard meter.
    The APM battery voltage meter is not very accurate. It was changed in software some time back to make it able to detect and log "brownouts" in the 5V supply voltage, but the voltmeter performance suffered. I don't know how good the DJI voltmeter is but in any case, they all work under load and will also see the voltage drop in connectors and wires.
    The PX4s voltmeter is excellent and the brownout issues were solved by it having its own 5V supply. Pizhawk hopefully too.
    Regards, Søren
  • SOLVED: The short answer is when the telemetry says that the battery is done there is another 8.5 minutes of flying time available. Have set up the voltage/current sensor properly now and all is fine. 12.5 minutes of flying time!!!! ( At last )

    A long journey to a very simple solution!

    These things are sent to test our resolve!

    Andy

  • Are they both steady and not jumping about in the air ? I noticed myself when i had something hanging off (foam leg not propertly attached) of deadcat with a APM, there was more vibrations and that motor itself got hotter. I also noticed that it seemed i got less flightime because of the cycling between lo and hi than average motor throughput. Perhaps something similar is happening on yours. The APM powered on is doing lots of big or small jumps and the much more varied speed changes is sucking your battery.

  • Partially Solved: OK ... So we have some progress and a partial result!

    I have flashed 2 out of 7 DJI ESCs to BLHeli v10.4 - As it stands I can't get the others to connect will work on that later today.

    I bought a clamp meter and its very obvious what is happening ...

    On the APM based copter I have 5 ESCs at DJI FW and One on BLHeli I powered up the APM, armed and ran at various throttle levels with the meter clamped on each of the ESC types.

        The ESCs with DJI FW are drawing 8-9A irrespective of throttle, I powered up to full throttle and the power actually reduced to 6.5A very very strange behaviour. So with this in mind, 9A x 6 Motors = 54A instantaneous With a 5000mAh battery ( 5000 mAh * 60 minutes ) / 54000mA = 5.5 minutes absolute max flying time ( flying to 15% battery gives 4.6 minutes ). All adds up to the behaviour that I am seeing.

        The BLHeli flashed ESCs draw current proportional to throttle, at 50% throttle ( assuming this is enough for a hover ) current is around 3.5A so in loiter mode I would expect ( 5000 mAh * 60 minutes ) / ( 6 motors * 3500mA ) = 14.3 minutes.

    I have absolutely no idea why the current remains constant when the DJI ESC is connected to the APM 2.5 ... I will redo the test tonight to make sure. One for the developers I guess what's very strange is the fact that the NAZA can drive the DJI ESC without problem. I am surprised that this is not a more common issue, I would have thought that F550 with stock ESC and Motors would be a common configuration since they are available as almost ready to fly kits.

    The work continues! Will keep you posted!

    Andy

  • Have checked the RC_SPEED and it is set at 399, this has been set through the last field test so should be as recommended.

    I was up until 1am this morning trying to flash the ESCs. Phew what a pain I got nowhere...

    I could not get an Arduino Uno here in Jakarta so went for Leonardo but the and also bought the USPASP USB programmer both of which seem to have issues connecting laptop to the programmer:

        I can not find specific instructions for an SiLabs with the USBAVP or BL Heli with the Leonardo board.

    So more questions:

    DJI ESC is effectively a Turnigy Plush 30A with an SiLabs processor.

    1) Can I program this with a) SimonK Firmware or do I have to use b) BLHeli?

    2) Can I use Leonardo or USBASP to complete option a) or b) above.

    Ideally I would like to have SimonK firmware .. is this possible?

    I have an Arduino Uno arriving from the UK on Monday maybe this is the answer.

    I will write this up and post once I am over the hill and into plain sailing mode ( or heli hovering :) )

    Just watched a video we took at the weekend, loiter is beautiful, rock steady but bloody short!!!!!

    Once flight time is resolved I will tell you about my inability to circle!! [:-(

  • Hi Scott,

    I tried setting RC_SPEED, I actually did that in a controlled way, I strapped the copter to the dining table and tried various settings for the RC_SPEED I monitored the current draw at various throttle levels, it did not make any difference.

    I have been doing some research since and it seems like the issue could be the pulse width on the output side of the ESCs. This would follow since the motors do get quite hot. As I mentioned, I plan to get the DJI ESCs to SimonK Firmware and I believe that you can play with the Pulse Width to the motors there.

    Waiting for an Arduino Uno to arrive so that I can get flashing... 

    What fathoms me is how can the difference be so big, since the rigs are identical F550 stock with DJI motors and ESCs???

    Andy

  • I don't think that difference is due to the controller, more likely something mechanical or possibly having your props on upside-down.

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