An intriguing cure for range anxiety allows any EV to take a road trip

You failed to mention another major problem with this solution: In the US and probably elsewhere, the speed limit when towing a trailer is 55mph. So on I-5 you have dropped from a speed limit of 75mph to 55mph. The reason for this drop is pure safety, it is very dangerous to have a trailer become uncontrollable at high speeds.

The next question is if the users of the trailer are smart enough to understand the safety aspect. (Lots of money does not necessarily translate to lots of brains.) Do they know to slow down when the trailer starts fish-tailing or do they try to "drive through it"? Following the accident rates and stories surrounding these trailers might be an interesting "Darwin" study.

This battery trailer, which could otherwise be known as (in RV parlance) the "Bat Toad" or the "Electro Dinghy" is one solution to the inherent range limitation of current EVs, even though very expensive and heavy. As mentioned it does offer the potential for trailer swaps at stations which would be even quicker than current full tank re-fueling, but only if volumes of these become high enough to support stations across a broad geographical range - not likely at current costs. (At $20k each who would own the exchange units, sitting around waiting for the swap customer to come in?)

But this just highlights the need even more to better address EV range limitations and battery re-charging. While I give Tesla and Nissan a lot of credit for setting up re-charging stations keep in mind that that they are far from a good solution. They are an enabling solution only as full battery re-charging can take many hours - so what do the driver and passengers do while waiting 8-10 hours during the day? Even Tesla's super-charger is much faster but you still have a wait to achieve only a 50% charge.

I think the better long term solution would be to have EVs use standardized battery packs/cells (that are common across many brands and models) which can be quickly swapped out at service stations. So the driver would pull in to a station, have his dis-charged batteries removed and fully charged ones inserted. This would require charging a Kw hour fee for the difference in the total electrical charge between the new batteries and the dis-charged ones, which should be easy enough to do, but it allows the driver to exchange batteries and immediately be on his way. Very similar to the propane tank exchange process many use now for their grills.

Tesla has already announced something like this (with Elon even demonstrating it in a video) for their Model S, where the vehicle is driven onto a platform where automated machinery unscrews the 17 bolts holding the heavy battery in place on the bottom of the vehicle, the dis-charged battery is removed and a fully charged one re-bolted back in place - faster than a current petrol fill-up. It's very slick except that that these stations have not yet been built, they would apply only to Model S (so far), and as announced it was not really a battery exchange as Tesla press made it sound like the owner would have to return to that station to re-claim his original battery and re-install it after being re-charged. Kind of a clunky process because the driver may not ever be planning to return that route. Points out why a full battery exchange program would work better as I don't think owners really care about battery ownership per se, they just want to be able to travel distances as quickly and easily as possible. But these Tesla exchange stations have not yet opened, maybe because they would not work for the Model X or Model E? Don't really know, but again it points towards the need for standardized battery cells that could easily be exchanged across at least different models.

Part of the Tesla Model S problem is that it uses one large, flat, very heavy battery - so automated tools which can manage that weight have to be employed. So why not use smaller standardized cells that would be easier to handle and which would allow for various quantities to be used on different models? Rather than requiring expensive "nut-runners" and hydraulics the cells could simply slide in and out by hand, kind of like replacing the "D" cells in your flashlight, where you have 2 cell, 4 cell or even 6 cell versions. Presumably the upcoming Tesla Model E will have less battery capacity in order to keep the vehicle price lower, but that really just means fewer cells.

But as I have stated before, I give Tesla a huge amount of credit for showing how to produce an EV which is practical, has decent driving range, and which is desirable. As with any new technology there is a learning curve in the subtleties as various issues and concerns are addressed, but Tesla has already crossed the biggest hurdle by proving that a true EV can work, and work well.

This is certainly not a new concept. There have been announcments of several range extending trailers. There are many problems not the least of which is the electrical high voltage and high current connections. also even my friends who pull trailers only occasionally say the trailer is a hassle in a parking lot and "Backing-up--Just FORGET It !", A range extender must be light perhaps using a Gas Turbine and alternator as Jaguar does in their concept cars then place it above the trunk looking like a piece of luggage but streamlined.and that price is a death knell for marketing. TESLA demonstrated that a bigger battery pack is the most "Elegant" solution!"