Voltage of battery going up and down all the time

I have the power module, but the voltage of the battery keeps going up and down non stop. Every second its different. One second 11 volts, the other 10.6, the other 11.1 and so on. My quad did 2 landings because of low battery when i have set it to 3.5/cell and the voltage was 3.75. But because of the up and downs it decided to land. Why is that?

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  • Moderator

    The voltage calculations and conversions within the APM code are fairly rudimentary. There is just a basic filter to smooth out the voltage number reported. The power modules are also notoriously inaccurate and as most of us are used to millivolt accuracy it's 1/10th volt accuracy (at best) causes a lot of issues. There are lots of reports of voltage inaccuracy problems. The air speed sensor has a similar problem with inaccurate and fluctuating readings on the ground in still air.

    If you check the voltage with a DVM it should not be fluctuating. A new PM may or may not solve the problem, so sometimes to learn and adapt to the idiosyncrasies is the easiest option unless you'd like to fix the code or redesign the PM.

  • Moderator
    It's probably best to try and help this member out with their issues rather than having companies trying to sell them their products and derail the discussion.


    sarah lee said:



    Rado Ino said:

    210$ for 10000 mah batttery/ No thank you!

    You are welcome, what kind of price can you accept?

  • See my comments on this post , previous page.

    Voltage Lag is a potential cause of your problem.  A good review of your logs can confirm or deny this.  Compare the battery voltage and current over time.  As current go's up voltage go's down.  When you land and disarm the log will show the voltage rise once the current drops to zero. To set your failsafe the voltage lag this must be considered.  

    The "C" rating tells you how much current the battery can supply.  If your current is more than 50% of the max current draw then you will have increased voltage lag.  Lots of good information on this on the lipo blogs.

  • 11 volts does not sound like 6s...

    Voltage can change as the load increases. How much? Depends on lots of fsctors.
    Can you see a relation between the load (current) and the voltage drop? Or are the fluctuations more random?


  • Rado Ino said:

    210$ for 10000 mah batttery/ No thank you!

    You are welcome, what kind of price can you accept?

  • 210$ for 10000 mah batttery/ No thank you!

  • Recommend you use a new battery one, such as Tattu 10000mah battery 6S, high quality, reliable power.

  • I havent. And i dont think i have mentioned what ESC im using :) Im using 20A esc. I guess i will just order new power module and wait for it.

    Harry Courter said:

    Well a bad power module is better than voltage lag creating your problem.

    Have you measured your current during a flight from an independent source?

    Why are you using 70A esc's when you hover at 10A?

  • Well a bad power module is better than voltage lag creating your problem.

    Have you measured your current during a flight from an independent source?

    Why are you using 70A esc's when you hover at 10A?

  • I had a similar problem like that.  It looked fine on the bench but when I went to fly it dipped a lot and caused it to fail safe and land.  I later determined that it was caused by a damaged power module.  The module providing power was not damaged but the electronics that was detecting the voltage was bad.

    I ended up replacing the power module and all was well again.  I think what happened was that one of the pins shorted to the current pin and damaged the output reading.  After fixing this issue the voltage reading were never right.

    So it could be just a bad voltage monitor.

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