Today’s EVs are in some ways a hack. The energy contained in the battery is far less than in a tank of gasoline. To achieve range, most EVs are more aerodynami

Today’s EVs are in some ways a hack. The energy contained in the battery is far less than in a tank of gasoline. To achieve range, most EVs are more aerodynamic than your average ICE car. Towing a battery out back would be horrible for aerodynamics and thus horrible for range. Furthermore, EVs achieve good EPA ranges by doing better in city driving where they can recover energy via regenerative braking. They do worse at highway speeds since air resistance increases superlinearly with speed. Towing something bad for aerodynamics at highway speeds would be doubly horrible. Lithium batteries must be kept within a temperature range. Too hot and they combust because the liquid electrolyte is flammable. They generate waste heat when discharging. If you don’t get rid of that heat, your battery will combust. That is why EVs have heating and cooling systems for the battery. Your towed battery, if you are extracting power from it directly, will need that. Phones deal with too much heat by shutting down or throttling CPU speed. Some EVs have crawl mode but not for excess heat AFAIK. Just buy an EV with more range. I think the Chinese standards could allow for different amounts of energy contained by the battery. For example, you can use different battery chemistries with the same form factor (nickel vs iron). In other words, there are additional costs borne by an EV with a towed battery beyond what you would have with an external battery pack for your phone.