I had a little time to surf the web for EV replacement battery packs and felt faint when I saw some of the numbers.
*$15,000 for the Nissan Leaf.(about $625/kWh)@ 24 kWh.
*Tesla's internal accounting/purchasing works out at ONLY $500/kWh.
*16-16.5 kWh looks common for 'entry-level' EVs.
Any range-extender-trailer with only a battery pack,at these costs,would be something to 'rent' for an outing,and not necessarily 'own.'