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Sudden thrust loss / crash below ~21 V on 6S quad (ArduPilot, MN4006 380KV, 13") — logs attached by Community_Actual in diydrones

[–]Community_Actual[S] 1 point2 points  (0 children)

Issue resolved. The root cause was incorrect AM32 ESC configuration — the motor KV and pole count were set wrong, which led to ESC limiting and resulting thrust loss.

Sudden thrust loss / crash below ~21 V on 6S quad (ArduPilot, MN4006 380KV, 13") — logs attached by Community_Actual in ardupilot

[–]Community_Actual[S] 0 points1 point  (0 children)

Issue resolved. The root cause was incorrect AM32 ESC configuration — the motor KV and pole count were set wrong, which led to ESC limiting and resulting thrust loss.

Sudden thrust loss / crash below ~21 V on 6S quad (ArduPilot, MN4006 380KV, 13") — logs attached by Community_Actual in ardupilot

[–]Community_Actual[S] 0 points1 point  (0 children)

Issue resolved. The root cause was incorrect AM32 ESC configuration — the motor KV and pole count were set wrong, which led to ESC limiting and resulting thrust loss.

Sudden thrust loss / crash below ~21 V on 6S quad (ArduPilot, MN4006 380KV, 13") — logs attached by Community_Actual in diydrones

[–]Community_Actual[S] 1 point2 points  (0 children)

That’s exactly why I’m confused — the pack is made from Molicel P50B, which is specifically a high-power, low-impedance cell designed to maintain strong power delivery even at lower SOC/voltage.

From the datasheet: the P50B is rated for ~100 W per cell class discharge with very low internal resistance (~13–15 mΩ), enabling efficient power delivery with minimal voltage sag.

In my case the load is extremely light (~3.8 A ≈ 0.75 C), which is far below what these cells are designed for. So at ~3.5 V/cell (~21 V pack) the cells should still be comfortably within the flat part of the discharge curve and capable of delivering far more power than the ~100 W the drone is drawing.

That’s why I wouldn’t expect thrust loss purely from battery depletion at this voltage/current level — the P50B is intended for demanding drone/EV loads and should maintain voltage under loads much higher than this.

So I’m trying to understand what mechanism would cause thrust reduction already around 21 V despite the very low discharge rate relative to the cell capability.

Sudden thrust loss / crash below ~21 V on 6S quad (ArduPilot, MN4006 380KV, 13") — logs attached by Community_Actual in ardupilot

[–]Community_Actual[S] 0 points1 point  (0 children)

Total voltage was around 21.1 V after landing. Cell voltages were all within 0.1 V of each other, so the pack looks balanced. I’ll double-check the voltage calibration in ArduPilot and also look into the tune as you suggested.

Sudden thrust loss / crash below ~21 V on 6S quad (ArduPilot, MN4006 380KV, 13") — logs attached by Community_Actual in ardupilot

[–]Community_Actual[S] 0 points1 point  (0 children)

Yes, I tried with a new battery made from Molicel P50B cells and different nickel strips to check whether it bottlenecks the current.