How did Tesla make some of its cars travel further during Hurricane Irma?

Tesla drivers who fled Hurricane Irma last weekend received an unexpected lesson in modern consumer economics along the way. As they sat on choked highways, some of the electric-car giant’s more keenly priced models suddenly gained an extra 30 or so miles in range thanks to a silent free upgrade.
Read more: https://www.theguardian.com/technology/shortcuts/2017/sep/11/tesla-hurricane-irma-battery-capacity?source=Snapzu