While swapping battery packs is a possibility, there are (as mentioned before) a number of problems. You need to have standardized battery packs suitable for a very wide range of vehicles, but larger vehicles will need multiple packs, and the infrastructure to remove/install them. The position of the packs would have to be standardized too, so that automated equipment can remove and install them – you don’t want Joe Average (or grandma) trying to manhandle a heavy battery pack! This might place too many constraints on vehicle design for people to be happy with.
Should I pay the same price to “fill up” a half-discharged battery pack (because I’m about to drive a long distance with no service stations) as someone who has run theirs flat? How about the condition – should I pay the same price to receive a pack that will barely hold a charge (due to age and abuse), while the next guy gets a brand new pack? Some sort of tamper-proof condition monitoring would have to be built in to each pack, so its history is known. And of course, there’s the chicken and egg problem: no one will buy these cars and trucks until there’s a nationwide infrastructure in place to “refuel”, and no one will want to build the infrastructure until there’s a demand for its services. Maybe this would be a good government project, with the system to be privatized once it’s up and running.
Per the video in the above link, I hate the thought of a battery inserted from the bottom, unless it had a well-sealed door. Think of the water, slush, salt, and whatnot that would splash up into the battery compartment otherwise! Even then, I’ll bet you’ll see lots of cars with iced-over battery doors. Loading from the side might be an improvement. In any case, batteries are heavy, and you have to watch your vehicle’s weight distribution (maybe a minimum of two packs – one in the “engine” compartment, and the other behind the rear seat?).
There was another YouTube video which I found hilarious. Some guy actually festooned his car with windmills and generators! Of course, he never heard of the First Law of Thermodynamics.
Back in the mid 70’s, there was talk of composite material flywheels used to store energy. Supposedly they could be lighter than batteries and “charge up” faster. Whatever happened to them? To cancel out gyroscopic effects, they would be installed in counter-rotating pairs.