I may be incorrect, but based on those discussion it was always possible to operate the ICE and charge the battery.

"Always" is too strong; it's "usually". The amount of

*power* (measured in kW or horsepower) needed to move the car varies from moment to moment. The amount of

*energy* (kWh) needed is the integral of power with respect to time. For simple cases you can simply multiply: 8 kW, times 2 hours, equals 16 kWh, for instance.

If you're accelerating from 0, or going uphill, though, it can take more kW (hp) than the engine actually provides: the Karma has 300 kW (403 hp) of electric drive. Even accounting for the de-rating, you could easily use over 200 kW for a short period. The engine/generator produces a maximum of 175 kW, so in order to use 300, or 250, or even just 200 kW, you must get some kW from the battery.

But you can't accelerate from 0 continuously, nor go uphill forever. Eventually you hit cruising speed and flat or downhill areas.

*Then* it's possible for the engine to recharge the battery, since the available 175 kW is way more than the needed 5, 10, or even 70 or 80 kW you might need to sustain speed (depending on actual speed).

The current software won't do it, though. To bring the battery level up, you must drive up a mountain in Sport (holding it at 26-or-fewer miles), then go down the mountain using regeneration to push the level higher, take the car out of Sport briefly, and now you can hold the new level provided it's no higher than 26. (I have done this going down the mountain from Alta/Snowbird, and down the Sierras from Tahoe towards Sacramento or Reno.)