- Your vehicle design will be less efficient and more expensive than one without the constraint of an easily-removable battery.
- Just like with phones, removable batteries mean that you have more ingresses for water and dirt, hurting reliability.
- You have to standardize on battery sizes and interfaces. If some new battery technology comes along, or you want to change the chassis (to improve crash safety, for example) you'll have to create a new standard.
- In modern EVs, batteries have liquid coolant pumped through them. This lets the vehicle keep the battery at optimal temperatures for charging, discharging, and avoiding degradation in hot climates. Swapping batteries means coming up with another solution for controlling battery temperatures.
- In addition to specially-designed cars and batteries, you also need specially designed swapping stations. Again if you ever change the standards, you'll have to upgrade these stations.
All of these issues mean that battery swapping drastically increases cost and complexity for little benefit. A swap will take five minutes, while charging to 80% can take as little as 15 minutes. There's also the issue that batteries are valuable, and the owner of the vehicle probably wants their original battery back (or at least one without more wear & tear). Then you get into issues of compensating or charging people thousands of dollars depending on their new battery's degradation level. It's much simpler to give up on swapping and focus on improving charging speeds, which is exactly what Tesla did.