Issues with compass calibration and high offsets


I am trying to build similar drones and I am trying to find the perfect compass location. Here are two logs that have only one difference. The difference comes from battery chemistry. One battery is a Liion and the second one the Lipo battery. I see huge differences between the compass readings between two different batteries.
My second question is about the normal values for the compass offsets in flight. I know that It should be somewhere between -400/+400 but on some of the axis my values are over these values.

First flight with LiIon battery first image is the internal compass, then the second one that is on the carrier board and the third one is an I2c compass that I can move around and find a better placement.

Second Flight with Lipo battery, sequence of the pictures is the same, same calibration, only battery difference-

My question now is are the first offsets too high and what can I do to reduce them other than the usual “try putting the compass away from the source”. I would like to keep using the Liion battery, because I get around 10-15 minutes more flight time compared to lipo battery.

Flight logs are here -

The main rule remains unchanged:

  • putting the compass away from the source of high magnetic fields

But you can do How to methodically tune (almost) any multicopter using ArduCopter 4.4.x section 4 - Second flight: MagFit and tell us if it helped :wink:

I can do that, but i would rather fix the source. I will do the magfit flight and see what the results are.

Fixing the source of the issue means putting all compasses away from magnetic fields.
And/or disabling the compasses that are close to those high magnetic fields.

Magnetic fields are caused by electric currents, so batteries and high current cables are to be avoided.

Magnetic fields cause high offset values. MagFit will try to offset the offset values back into a normal range.

“I am trying to find the perfect compass location.”

I like to place the GPS center in the body above the FC but i don’t think it makes a ton of difference… I think the quality of the GPS has more to do than location, Most of the mRo compass work well inside the frame close to the hardware so having a mast is a little old fashion and can sway in the air. I also try to limit the amount of screws in the frame.

I am using bmm150 compass as an external one. There are 6 screws in total for the whole electronics. And there is a 4in1 esc with twisted motor cables.

Here is my new rig, i normally use a better GPS.