I'm not the first to bring this up, but how's this for an EV (Electric Vehicle) paradigm. Normally, you drive around with a battery pack that is enough to get you to and from work; what you might call the commuter load. But say you want to go to grandmas, a metaphor I like to use for the perennial great North American road trip. Well, if you live in Montréal, PQ, Canada and your gran is in Toronto, OT, 550 km away. You EV can't make it; it's only got a 160 km range. You could of course rent an ICE (Internal Combustion Engine) Vehicle to make the trek but renting a car is such a pain.
But what if you could extend your EV's range for those days when you're visiting grandma, but didn't want to lug around all that extra battery when you're just going to and from work? Wouldn't it be nice of an EV came with some standard Auxiliary Battery jack in the trunk where you could hook up supplemental battery power special for your trip?
With an auxiliary battery pack, you could potentially quadruple your battery capacity with some extra cell packs in the trunk — properly cooled — which would add to the car's weight and thus decrease its mileage but would probably be enough to get you the entire 550 km to grandmas. The question remains what you would do with the batteries once you've arrived. One possibility is you just charge the factory and auxiliary over a few days and nights to bring them up to capacity for the return trip. This would be the wisest decision of if you owned the auxiliary batteries outright. But if you owned them, you'd have to worry about storing them and that could get inconvenient. And what about the long-term storage of the auxiliary battery? Who needs the hassle?
And alternate solution could be to simply rent the auxiliary batteries for the purposes of your trip. You'd go to a battery rental place before leaving, and they would rent you fully-charged batteries. When you arrive at grandma's, you go to another local battery rental joint and return the now-depleted batteries you rented. You then repeat the same process when you're getting ready to leave grandma's. Now, the auxiliary batteries don't have to be your standard lithium batteries that are in your EV. Instead they could be high-capacity cells that can only be recharged with special equipment. So you return the depleted battery and the technician takes it into the back room and hooks it up to the special electrochemical equipment that restores an electric potential to the auxiliary unit. A few days later, that battery is ready to be rented again as fresh as the day it was first constructed — or at least nearly as fresh, depending on how the recharge process degrades capacity.
That's how I would solve the range problem with EVs. You don't need a backup ICE or some other complicated equipment you need to lug around with you the 97% of the time you're just going to work for the 3% of the time when you're visiting grandma. It's a simple, clean and efficient solution.