Exactly! The usable capacity of our 60 Ah battery pack could provide the energy equivalent to that contained in ~½ gallon (~2 liters) of gasoline yet I could drive ~100 miles (~160 km) on that energy under ideal conditions. That's the equivalent of 200 miles per gallon (1.2 liters per 100 km) which is far more efficient than any ICE vehicle.
Depends on where you drive: city and rex works fine at 6%. Highway and rex does not work at 6%... you'll not be at speed with traffic and the rex can not keep the battery charged effectively. So better to use it earlier on highway trips, refuel while the battery is higher capacity.
The fact that the charge level decreased by ~25% over 60 miles while driving 85 mph demonstrates that the REx generator power output is insufficient to propel an i3 at 85 mph without power from the battery pack. If the charge level decreases to 0%, your i3 would not be able to continue driving at 85 mph. I recall some REx owners claiming to be able to drive no faster than ~30 mph on REx generator power alone (i.e., at a 0% charge level).
Maybe uphill, but on flat road definitely faster, more like 65mph. Once up to speed a car does not require that much power to keep it's speed. My EV Kangoo has ~15-20kW continuous power and can sustain 60 mph. Uphill is a different story.
When I first got my i3, I didn't know about HSOC and several times I drove it until the battery was at zero and it continued to drive on the highway on Rex only with seemingly no problem and no apparent loss of power. I didn't do 90 on that trip, only 75-80, but it definitely kept up with traffic.
