[Snax]

As appears to have been brought up twice, BMW addressed this concept head-on with the i3 REx. Whether it succeeds well on that point is debatable, but I thought it was good enough to purchase a 2016 about 6 weeks ago.

Yes, it adds weight, but it's not a lot. Bottom line is that it can be thought of as an integrated genset with the charging while driving issue thoroughly honed for optimal efficiency at cruising speed.

I had been up and down and all over so many of the points discussed in this thread that it boiled down to this:

If you want range extending with a mass produced EV, purchasing an EV with that already built into it's design is the only practical way to go. Efforts to push or charge any other mass produced EV are simply going to end up overly complicated, troublesome, and more expensive in the long run - particularly if one is buying a car that is a few years old.

The flip side of this is EV conversions. If you already have one that you built or had built and can accept a charge on the move, do it!

In the end, as much as I wanted to convert my 02 Miata to full electric however, the cost factors involved in that simply did not make much sense to me either. To be clear - I would not build an EV these days given what is currently available on the used market for mass produced EVs. It would only be for love of a particular car to make that remotely pragmatic.

Bottom line: Unless you already have a converted EV, all other discussions surrounding this will ultimately cost more to implement when ready made cars already exist today that can do what you want - albeit with compromises. The only other solution as others have mentioned is to purchase the 'right tools for the right job'. I.e., if you want EV efficiency for most of your local driving, get a pure EV, and if you want something that can do 1000 miles in 15 hours of driving, get a gasser. Everything else in between is a hybrid and is a compromise between ultimate efficiency at either end of the scale.

Don't try to reinvent the wheel, and don't try to make a knife work for a gun fight!