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Battery Issue???

Posted by mark bellncula on June 22, 2016 at 8:36am

I have a 2250mAh 11.1v 3 cell battery that I'm using for my 450 kit build, motors are 1000Kv motors. 

Using a Pixhawk with the PX4v1.3.3 flight stack, loaded via QGC.

And I'm using an Imax B6 charger for the battery. Battery is brand new.

This is the issue; I will plug the battery in, with the props off, as a system check. I can throttle it up all the way, no problem. QGC says batteries are at 100%. External voltage meter says all 12.1, no1 4.03, no2 4.03, no3 4.06. 

System check looks good, so I put the props on.

I get the UAV up and within seconds, QGC tells me that the battery has dropped to 33% and the Pixhawk battery alarms go off. The external voltage meter, that is set at 3.6, does not go off. 

I keep it up for a few more seconds and the battery level drops to 17% and the alarms go nuts. I set the UAV down, for a flight time of mere seconds. 

I will then unplug the UAV from the battery, wait a second, plug it back in and reboot. QGC will say the battery is still at 100%. External voltage meter hasn't changed. 

So with the props off I have no issue, but as soon as I put the props on, the battery can't seem to handle it.

What am I doing wrong?

Thanks you for any insight.

Cheers!

_M

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Replies

    • mark bellncula > Harry Courter June 30, 2016 at 11:29am

      I didn't lose a cell, the other dude D Ohlarik lost the cell.

      I did another test flight today, and I got the same results. I'll detail my steps in this thread in a few.

      _M 

      • mark bellncula > mark bellncula June 30, 2016 at 1:05pm

        Okay!

        To reiterate, I'm using a 2250mAh, 11.1v 3S1P battery on a 450 quad kit build with 1000KV motors with 30A ESC's, and I'm using the PX4v1.3.3 flight stack.

        Attached are screenshots of my power and battery settings in QGC. From what I know, which is apparently nothing, those setting are correct.

        And these are pix of my battery just after my failed test, with the readout from the voltage meter that reads ALL 12.2, with cell1 reading 4.04, cell2 4.03 and cell3 4.08

        3702747816?profile=original

        3702747858?profile=original

        Though, I haven't been keeping a log of mHA use I have been sure to discharge the cells to at least 3.6v before I re-charge.

        What am I missing? I'm a total noob at this, but with my extensive history of technical VFX work, I suspect my problem is a minor detail that I am completely unaware of.

        Harry, I do have an ecalc account but the input fields are so detailed and I just don't know what to input. Again, I'm just a noob.

        Alasdair, thank for the input, but it was way over my head. What I can tell you is that I've only charged and discharged the battery less than a dozen times. Also I live at 10,000 feet, so all my charging cycles have been in a cool environment.

        Don, should I just wait for the new PX4 developer build and latest QGC daily build?

        I'm trying really hard to figure this out on my own, before I bite the bullet and hire a drone tech, who's going to see my error immediately, I suspect.

        I'll have a link to a video of my failed flight test up here soon, stay tuned.

        Cheers everybody!

        _M

        Screen Shot 2016-06-30 at 12.31.32 PM.png

        Screen Shot 2016-06-30 at 12.32.23 PM.png

        Screen Shot 2016-06-30 at 12.31.47 PM.png

        • mark bellncula > mark bellncula June 30, 2016 at 2:14pm

          Here's the vid.

          and here's the direct link;

          https://youtu.be/_CZJRHJ7AMU

          If you can hear QGC, in the windy background, you'll hear the alarms go off immediately.

          I bounced the landing and it rolled over onto the front rotors. I immediately disarmed, and set it upright. Then I moved in close to get a shot of the alarm lights.

          Any ideas?

          Cheers!

          _M

    • Alasdair > Harry Courter June 30, 2016 at 6:47am

      Another problem is, the energy put in, unfortunately is not what you get out, after subtracting resistive losses due to failing cells, or even healthy cells, there is always some loss. When the cell has plated off from over charge/discharge it struggles to deliver anywhere near normal current, but can still accept a majority of it's capacity in amp hours. The wasted energy is what heats the pack and usually causes puffing by liberating oxgen from poorly assembled cells usually containing too much water within the polymer electrolyte, but that's another story.. Another thing often overlooked is the temperature of the battery during charge, this has a major affect on terminal voltage, and the typical 4.23v/cell is only correct for 50-60 degC and yet at 10 deg C it should not exceed 4.0v/cell, above this and excess electrons will free lithium to bond with oxygen and make lithium oxide, and goodbye battery. Most chargers do not give you any option here, let alone being smart enough to calibrate their termination voltage to pack/ambient temperature, so the best thing to do is charge them in a warm place to maximise life within spec. I built a warmer for use in our low temperature climate, it regulates temp within a few degrees, compensating for pack heating during charge, but that's drifting off topic..

  • George Kelly June 23, 2016 at 12:29pm

    Did you calibrate the power module?

    George

    • Don Gagne > George Kelly June 29, 2016 at 9:59pm

      If you wait two days, then flash PX4 developer build and download the latest QGC daily build. Then under Power you should see support for voltage and current calculators which allow you to calibrate the power module. The work for this is complete, it just needs to work it's way through the build systems which is taking a little while due to build provider problems.

      • D Ohlarik > Don Gagne June 30, 2016 at 3:52am

        Thanks for the heads up!  I will be on the lookout!

    • D Ohlarik > George Kelly June 23, 2016 at 2:15pm

      Hi George - I am trying to figure out how to do that now.  Looks like in QGroundcontrol, under Parameters / Battery Calibration, I just need to manually enter values?  Or is there some automated process to do this?

      Thanks!

      Derek

      • mark bellncula > D Ohlarik June 27, 2016 at 9:54am

        Derek,

        Looks like we have the same issue. I only have one battery though, so there's no way for me to tell if it's a PX4 Flight Stack error or a battery malfunction. I understand that I should just get another battery to test that idea, but I want to make sure I'm using a proper battery for a 450 1000Kv quad. And everything I have read and asked confirms that a a 2250mAh 11.1v 3 cell battery is proper. 

        Does your issue occur across different batteries?

        Cheers!

        _M

        • D Ohlarik > mark bellncula June 27, 2016 at 1:43pm

          I am waiting for another battery to show up.  Changing the battery paramters DID make the issue go away.  However, immediately after that, I lost one of the cells in the 3S battery, so its dead.

          When the new battery arrives in a few days, I will continue tweaking the battery parameters.  But it did have an effect.  I just want to be sure I set it to accurately show a low battery when it actually is low.

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