SaltyNZ:

 

I would not be shocked if that's what Tesla does - after all, they offer the ability to upgrade your range via an over-the-air update to the car, and bits don't magically make new batteries appear out of thin air. But there's nothing new about that. Disk drive manufacturers have been doing that for decades to improve the reliability (and also speed, in the case of SSDs) of their drives, and every form of error correction is fundamentally the use of some hidden extra capacity.

 

In the case of batteries, you're trading some initial extra range for a guaranteed longer life with a reliably steady range. It makes sense to me.

 

Tesla doesn't have as much of a buffer as other companies. The only time Tesla allows you to unlock more battery with an in-app purchase is when they've sold a low-capacity configuration of the car with the same pack from a higher capacity configuration, such as the Model S 70D which had the same pack as the Model S 75D.