This surprised me the other day. We went for a hike, and left the car parked at the trailhead, elevation 5249 ft. I failed to note the temp on arrival, but it was cool, let's say 60s F. The car was in full sun, toasting nicely while we hiked for almost 3 hours. Upon our return to the car, the outside temp was up to 84 F. The battery was at 66%. Driving down the mountain, we had regen dots for about 3.5 letters (PRND). What the heck? Plenty warm, battery not too full. Why limited regen? Any theories?