Powerfool wrote:I really wish that they just had the ability to have auxiliary batteries that could be added/removed/upgraded as necessary. Maybe just a pack that goes in the cargo area. When you need extra range, add them... when you don't, remove them and drop weight.
The i3's large format battery cells connected in series makes doing this difficult because the battery pack's output voltage must remain within a certain range. Adding more cells in series would increase the output voltage above what the electronics are designed for. Adding more cells in parallel would maintain the correct output voltage range, but an auxiliary pack would need the same number of cells as are in the standard battery pack connected in parallel, so you'd need to double, triple, quadruple, etc., its capacity and thus weight.
Extending the battery pack cooling system to an auxiliary pack would be challenging, especially because the i3's battery pack coolant is pressurized refrigerant rather than the no/low pressure glycol coolant used by other EV manufacturers. The i3 would need a larger capacity A/C compressor and heat exchangers to deal with the additional heat.
Tesla's use of small format battery cells has allowed it to build battery packs of different capacities using different numbers of these cells arranged in various series-parallel configurations. This would make adding an auxiliary pack easier for Tesla.