The IC 7300 in the videos below was set to Emergency Tuner mode and connected to a dipole antenna that required an 8:1 impedance match (88ft dipole @ 25ft). The radio was set to 50 watts output (max for Emergency mode) and uploaded some email with attachments via Winlink for 20 minutes continuously on 80m. This created a duty cycle that heavily leaned towards being in transmit state. The power supply voltage was set at 13.8v.
The Temp stayed cool at 4 bars, the Voltage stayed high enough for full output power (about 45 on the power meter) and Current peaked at about 10A. The ATU components as seen by the removed bottom cover did not heat up at all by the end of the 20 minutes continuous operation.
If you turn the power up above 50, the output power does not exceed 50W (it seems capped at 50W). If the input power supply voltage drops much below 13.8v, the output power starts to fall off rapidly.
Video of radio guages after 6 minutes in Emergency mode at 50W connected to 8:1 match dipole.
Video of radio guages after 20 minutes in Emergency mode at 50W connected to 8:1 match dipole.
Video of ATU.