I made a few measurement how important is battery orientation and mast lenght and that is good idea to trade off increase of drag resulted from vertical battery orientation for reduced magnetic interferences …
EDIT add photos for 120mm mast (note: data was normalised to max current of 50 amps)
Vertical battery orientation
Horizontal battery orientation
Hi @Jan_Zajicek,
Thanks for the post!
Re battery orientation, do you think this is result applies generally? e.g. not just with this particular drone and battery? As a minimum it shows that it is likely that the magnetic interference changes significantly with battery orientation.
Also I guess “vertical” is here the thin edge of the individual cells are pointing up-and-down (e.g. battery cell edges are visible when looking at the battery from above) while “horizontal” is when the thin edges are oriented so they are left-right? Another possible interpretation is the battery has been rotated 90degrees when viewed from above.
Re mast height, I’ve always heard from @CraigElder that the strength of the magnetic field falls with the distanced cubed (e.g dist^3).
Thanks again for the post.
Hi, my pleasure to share same info with you. You guys make really amazing job with ardu!
I think that this should be general rule. Friend of mine got similar results when he measured impact of battery orientation. I think that this rule will be the more visible the bigger battery is used (for the measurements I utilised Li-Ion 6s2p battery). I gues that differences will be also in battery chemistry (Li-Ion > Li-Pol), but this I can not confirm.
Regarding mast lenght I meassured that every additional 1 mm reduced interferences by 0.8%. It is not cubed - lets say it is 1:1 ratio (1mm : 1%). True is that mast lenght has significant impact but less than battery orientation.
I add photo documentation what I mean vertical and horizontal orientation.
My experiments show that only mag interference source of UAV is battery.
I found one thing with 6S3P Li-Ion 21700 batt.
No matter horisontal or vertical cells. You will have huge interference even at 15 cm distance.
But if you place compass forward or backward of battery (perpendicular to cells) - at 5 cm will be very ok. (About 15-20% at 80% throttle.
Same happened with LiPo.
So Jan made right decission to place battery vertical under Compass.
it does not make sense “No matter horisontal or vertical cells.”. of course it matters. there is nothing like “place forward of backward of battery”. please describe with picture. thanks.
Please see this wiki entry for an explanation of how the magnetic fields and interference works
https://ardupilot.org/copter/docs/common-magnetic-interference.html#maxwell-s-equations-the-magnetic-field-on-the-axis-of-a-current-loop
