Odd AC behavior

I just came back from a 3000-mile road trip, hopping National Parks in Utah, Wyoming, Montana and noticed something odd about the AC operation. It first happened after 3 hours into the drive from SoCal to Vegas, the AC performance gradually dropped during the long uphill climb to Baker. The outside temp was only 87-92*F. The AC air slowly lost its cool and the amount of air blown out the vents was also weaker. The SOC of the traction battery was at 4 bars and sometimes dipping into 3 bars. After 20 minutes, I decided to turn off the AC and rolled down the windows. Shortly after I took a 15-min break and did a visual of the engine bay... nothing seemed out-of-order.

Continuing with the drive I turned the AC back on and it worked normally. From this point on, I routinely turned off the AC for 10 minutes for every 45-60 minutes of operation or when heading up long steep hills with the SOC falling into 3-4 bars. It worked fine this way for the entire trip. I noticed the AC performance didn't suffer if the car wasn't going uphill and the SOC was above 4 bars. There were a lot of hill climbs during this trip and I thought the traction battery would crap out since it's 138k old. In Yellowstone, the SOC oscillated between 1-2 and 8 bars a few times a day due to the hilly terrain. But the Prius made it to the top of Beartooth Highway at 10,947 ft... slowly but it made it!. On the way back to SoCal, after descending the Cajon Pass, I kept the AC constantly on for the last 3 hours and it worked fine. No more hills or passes to climb I guess.

Has anyone had a similar experience? Does the ECU back off the AC load when the traction battery is way below its optimal SOC and the ICE motor spinning at full tilt during long hill climbs?

Beartooth Hwy


Traffic Control in Yellowstone

 

140k by the time I got home.

I hope my theory is correct since the AC compressor is electric.