For the Phantom 3 4K Remote Controller, what this the minimum charge level below which the RC functions are no longer reliable? The user manual does not mention this.

A Remote Controller low battery warning appeared today when the charge was below 30%. I continued to fly until the AC battery was at critical low level (10%). When AC landed, the RC battery showed 24% on the Status page.

So how much lower could I have gone on the RC battery before the RC fails?

I've left the RC on to discharge the 2600 mAh, 7.2 V LiPo battery in preparation of re-calibration. There's some warmth in the area between the LEDs and the two buttons topside. The left-most white LED blinks when the charge is less than 12%. The annunciator must be silenced every 5 minutes or so. Continuous beeping that can't be silenced by pressing the power button when charge is less than 10%.

I'm not asking for best or recommended practice. I'm asking for the lower limit.

Hello Airspace Explor, unfortunately there isn't such a spec.So it is recommended to keep enough battery level before flight or fully charge it.