Interfacing with the existing car's electronics gets into "right to repair" technology, with some manufacturers being more open than others. Unfortunately batt

Interfacing with the existing car's electronics gets into "right to repair" technology, with some manufacturers being more open than others. Unfortunately battery packs are very vehicle-specific. Hopefully we'll eventually see some standardized form factors so you can just install a generic battery. Until then, 3rd parties will have to make a different battery pack for each model they want to support. Most of the problem is just the physical dimensions and shape of the pack, but also there are a bunch of electrical connections, battery-management system (BMS) integration, coolant hoses, and so on that would vary from one vehicle to the next. Hopefully as the technology matures, batteries get physically smaller and lighter, and therefore easier to shoehorn into weird spaces.