Part 1 of the test is complete. I started at home with 100% charge, and turned on e-save (battery charge) and max regen before leaving. Even with e-save on, the first ~1.5 miles was using only battery (presumably because it was at low speed and low throttle) and the battery was down to 92%. After that, the main part of the drive was around 55-65 mph and used mostly ICE.A full charge starting at work would be an interesting test, but unfortunately I don't have access to a charger or power outlet at my work. The closest test would be to start with a full charge at home and use e-save the whole way to work. I am sort of curious to see how high the charge would be when I arrive at work. In theory it should stay at 100% but not sure if that would be the case. One way to find out I suppose.
By the time that I got to work, the battery did manage to charge back to 95%. Watching the energy screen showed that it was heavily charging the battery during deceleration as expected, though it did also have a slow charge (1-3 kW) during flat roads with steady speed and throttle conditions. I had read somewhere that the ICE generator could not charge the battery above 79%, but that does not appear to be the case, unless I was actually seeing that slow charge caused by very light regen.
I know that high throttle position alone will cause ICE to turn on in any mode. With e-save on, my observation is that a light/medium throttle position and a battery load of somewhere around 30-40 kW seems to cause ICE to turn on. I have no idea if that's actually how the programming works, but that was my observation on the drive this morning.