Why don't electric cars have batteries that are swapped, rather than recharged in the vehicle?

Thinking of applying what's done with radio controlled model cars for full size cars. Standardise on the battery form factor, and how batteries are removed (say from underneath a vehicle, or from a side) and electric filling stations could be built with a "robot" to swap from flat to charged... show more Thinking of applying what's done with radio controlled model cars for full size cars. Standardise on the battery form factor, and how batteries are removed (say from underneath a vehicle, or from a side) and electric filling stations could be built with a "robot" to swap from flat to charged batteries in 5 minutes. Deposit model on batteries [akin to propane tanks, but as part of purchase price of vehicle] then pay for what's used. Batteries charged over night when electricity is cheaper, due to there being less load, and only a little less production=easier on power grid.Profit for operators of such stations is due to the convenience. A new better battery technology comes along, simply get the new type of battery next time car is filled up.
Update: Thanks for answers so far, OK instead of having monolithic battery blocks, use modular "cubes" of say 2ft wide. change them from under the vehicle and hang them underneath the car. Plates, to keep them in will form a cover for the battery compartments. Few people look at the undersides of cars so it shouldn't... show more Thanks for answers so far,

OK instead of having monolithic battery blocks, use modular "cubes" of say 2ft wide. change them from under the vehicle and hang them underneath the car. Plates, to keep them in will form a cover for the battery compartments. Few people look at the undersides of cars so it shouldn't spoil the lines. If dimensions chosen carefully then it SHOULD be possible to fit them in a wide range of vehicles. pick up trucks can of course have more.

Weight to lift. something like a lifting pallet truck+ some air tools to undo bolts.

Quantity required. Why would so many be needed? Only need sufficient batteries to deal with 1 full days resupply. Thought electric cars did about 800 miles. if average use is 80 miles a day, that would work out at average of 1 complete battery recharge every 8 days. 1/8 th of the total number of batteries installed in vehicles should cover that.

New battery technology does cause changes to the voltage of an individual cell. But as batter
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