I think as EVs become more prevalent, something like
this makes more sense than carrying around spare batteries. I mean, who carries spare cans of gas with them any more?
If gas cars could tell you how many miles you had left in the tank, anywhere near accurately, they wouldn't run out of gas so much.
Where I see EVs run out of charge is on trips where a newish EV driver thinks he can go 80 mph, up hill, and ends up 5 miles short of making it to the supercharger. No one told him to charge enough to get a buffer, and to watch the buffer, and if it starts shrinking, slow down. But the EV tells you exactly how many miles you have left.
This Charge Truck (AAA) only gives you 5 miles of range. You call, and if there is a charge truck near you (like, where, Seattle?) they come out (might take a while) and give you a 10 minute charge. That's at 10 amps, like at your garage 14-50. They call it a fast charge.
Wouldn't it be easier to slow down 5 mph and make it to your charger?
Non Tesla Cars of course, have a bigger problem, running out of charge with only one fourth the range. But Teslas running around doing daily errands won't need a Charger Truck.
And Teslas out on the far wild freeways, 200 miles out, won't find a Charger Truck anywhere nearby. And they will probably need more than 5 miles.