NRALIFR wrote:
On Ford superduties, there’s a feature called “Battery Charge Protect” that enables the ECM to monitor the battery voltage when the parking brake is set, and the transmission is in Park, and it will vary the engine RPM from 600-1200 while large power loads are on the charging system. This is for using inverters, DC-DC chargers, etc while idling the engine. The ECM also monitors the engine temperature while in this mode, and won’t let the engine overheat.
Admittedly, I am not intimately familiar with with the exact functionality of battery charging on all Ford products as I have been retired for over 10 years.
However, what you described is the basic functionality of all "smart charging" system. That is, to maintain a minimum battery voltage at about 13.2V. If this requires increased idles speed, then it will be increased.
