Great idea about the battery trailer! With modern battery technology (e.g. NOT lead acid), you could probably keep the trailer relatively small & light so that it's more acceptable to people that aren't used to towing. Make it aero shaped along with a little additional cargo space and you've got something that might even improve the default range of the EV and avoid the need for an aero-killing roof rack... (though obviously if it's used for cargo too, it reduces the "quick change" capability... unless it was designed in such a way that the depleted batt pack could be slipped out and a new one slipped in easily at the service station). Heck, if it could help you get ~250-300 miles with the EV, then you're at a point where you'd probably want to stop for lunch/dinner anyway, so if it takes 10 - 15 mins to do the swap, it wouldn't all that much of an inconvenience.
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