Running into an issue after switching from 4S to 6S on my 5" freestyle build. Higher voltage batteries deliver more responsive thrust, effectively changing the system response - PIDs may be fine on one battery type and oscillatory on another. Getting fast oscillations at high throttle that weren't there before. Is this something voltage compensation should handle automatically, or do I need to retune? Frame is Source One V4 with XING2 2207 motors.

Running Betaflight 4.5 with default voltage compensation enabled but still seeing the issue above 75% throttle.

Betaflight's voltage-compensated D-term (VBAT_D_SCALE) helps, but some re-tuning may still be needed when switching battery configurations. Try dropping your D gain by 10-15% as a starting point, then work up from there.

Had the exact same issue when I went 6S. Set TPA throttle value lower than where D term oscillations start - if oscillation starts around 1800 throttle, try TPA = 0.75, 1750. Fixed it for me without touching main PID values.

Check your ESC temps too - 6S pushes more current and if your ESCs are getting hot they might be causing the oscillations rather than your PIDs being wrong. Too high D term can cause motors to get hot - do a short flight and check if you can hold your finger on the motors.