Sheky said:
If, for example, the RR after full charge is 75 miles:
After travelling, say 20 miles, the remaining range would be 55 miles, or hopefully even more
If it is less, how much less would be considered a problem?
Sheky, the Range Remaining (RR) algorithm in the iMiEV is actually very good, and has been discussed here on a number of threads. The more consistent the terrain and the driving style, the more accurate it becomes. Most of us have learned to really rely upon it with the recognition of where/how we have just driven. Sandage just gave you a good example of this.
The beauty is that single trips for almost everyone in the United States are so short that an electric vehicle like the iMiEV satisfies well over 95% of these needs. There's an excellent discussion of this specific topic here:
http://www.solarjourneyusa.com/EVdistanceAnalysis.php
If the trip or series of trips you're planning on taking exceeds your RR, then it's a simple matter of figuring out how to 'opportunity charge' somewhere along the way. For example, it's not unusual for us to rack up over 100 miles (160km) on our iMiEV in a day, and yet still have over "1/2 a tank" (8 bars) of 'fuel' left at the end of the day. You soon find out how convenient it is to have your own 'gas station' at home, and start off every day with a 'full tank'. Distant friends we visit soon get used to leaving their garage door open so we can plug in to either 120vac or their 240vac dryer outlet. Having driven EVs with a nominal range of 20 miles (32km), I know where the power outlets are at my doctor/dentist, supermarket, school, gym, etc., but am glad I now don't need to hassle with this in my iMiEV.
If opportunity charging is impossible (or there is not enough time to put back sufficient energy) for you to achieve your trip(s), you simply don't do it and use a different vehicle. For us, this is a rare occurrence, and the gasoline is getting stale in our hybrid/ICEs. The reality is beginning to sink in that for us it could probably be cost-effective to simply rent a car for those longer trips. Since it is all calculable in advance, there is NO 'range anxiety'.
In practice, the vehicle's single-trip range is just about anything you want it to be - YOU have terrific control over it with your driving style.
Do you have a specific distance problem you're trying to solve and how can we help you with it?