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Rapid descent in RTL

Posted by Sandy Sound on March 30, 2015 at 4:00am

Hi guys,

I had a very heaving landing in RTL today - the descent was much faster than usual, it literally almost dropped out the sky. I suspect my battery failsafe is set too low and the voltage tapered off quickly as the battery ran out and that was that?

I think I have lowered the battery failsafe to 10.2, so I will put it back to 10.5 if it is a lack of voltage.

Could someone please view my log and confirm?

I am running a pixhawk 3dr quad 2014 kit stock with radio telemetry, 11 inch APC slo flyer props, tarot 2d gimbal with gopro3+ and taranis transmitter, 

Regards,

Sandy

63.BIN

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Replies

  • Holt Lipman April 4, 2015 at 4:53am

    If you're using RTL as low battery failsafe then you should set the low voltage at 10.7.  At 10.5, you'll drop out of the sky again before the DIY gets to the correct RTL altitude.

    • Sandy Sound > Holt Lipman April 4, 2015 at 1:53pm
      Thanks Holt, I followed agentremnants advice and changed it to 10.8.
  • agentremnant March 30, 2015 at 5:27pm

    If you are using RTL on your failsafe.... I would highly suggest 3.6v per cell. I can tell you with certainty that once lipo cells hit 3.5, they RAPIDLY lose voltage. if you are in a windy environment and in loiter/poshold/auto, then your drone will spend even more energy than usual. 

    3.6v per cell is the best bet to avoid this. 3.45v per cell should trigger auto land and not RTL. 

    • Sandy Sound > agentremnant March 31, 2015 at 4:32pm
      That's good to know, I need to purchase a bigger battery and looking to move to a 4S. The 3S has been great for learning to fly.
      • DG > Sandy Sound April 2, 2015 at 6:14am

        The MS series might work fine for you then. The problem is buying before they run out of stock.

        • Sandy Sound > DG April 2, 2015 at 9:51pm

          Im not in a hurry at the moment, I will not be pressured into buying due to stock levels. If it is out, I will probably just buy something else.

    • DG > agentremnant March 30, 2015 at 6:44pm

      Just in case anyone is using Multistar high capacity batteries, they drop voltage rapidly. HK claims the batteries are 10c. I think it's more like 2-3c. Used in a light copter they are ok, but testing proved to me not to use them in much heavier than 2.5kg unless running in parallel.

      • Sandy Sound > DG March 30, 2015 at 7:37pm

        Thats good to know, I am using a Turnigy Nano-Tech 4000mah 45-90C.

        • DG > Sandy Sound March 30, 2015 at 8:44pm

          Actually even 2kg is probably the best weight to get the most out of the MS.

          • Sandy Sound > DG March 31, 2015 at 3:29am

            My rig weighs in at 2.3kg's. I have a minimOSD and immersionRC transmitter onboard for "shooting" with a separate battery (Turningy Nano-Tech 1000mAh 3S 25-50C) to drive the camera/gimbal/minimOSD/transmitter.

            I need to get more batteries soon...

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