I would take Tesla’s shown range with a cup of salt

https://www.cnn.com/2023/10/25/busin...aim/index.html

 

Of course, the range figures were always optimistic. Rated range is a proxy for battery health. He may never have gotten 310 miles to a charge, but the car was rated for that at its full original capacity. It’s still showing 90% of that, so his battery hasn’t degraded much.

 

has he tested how far he can get on a charge now, or is he taking Tesla's word at face value?

My parents have a model X and my dad who is the now biggest Tesla believer you will ever meet says his miles remaining estimates drops fast after the charge dips below 50%. That lines up with how Lithium batteries operate, the discharge curve is relatively flat until each cell reaches around 3.70 volt and then it has to cut back quick as to not damage the cells. He has never gotten the promised range starting new a year and half ago.

I drive that X every weekend when I visit them with the kids and shuttle them around, I like how it drives, but user interface is a nightmare, and the fact that the doors open with a button and the windows have to roll down and back up every time you open and close a door is not my cup of tea.

 

I don't believe there is a battery with a linear discharge rate.

 

That’s how many EPA miles the battery has at a full charge. It’s a battery health metric that’s calculated by the car.

It’s complicated because Tesla insists on defaulting to EPA mile ratings, but the trip computer is much more reliable. Mine was almost telepathic in how accurate it was on trips. Navigate to a destination and the car will give you an estimated battery percentage upon arrival. That percentage estimate takes into account speed, terrain, wind, and a bunch of other factors. Mine was almost always within a percent or two, is your dad’s Model X worse?

I was confident enough in that estimate to repeatedly roll into Superchargers below 5%, and I never got nervous.

Modern battery controls are a heckuva lot more accurate than what we saw in years past. If the truck says 40%, it means it. The readout in my Model 3, EV6, Model Y, and my F150 have always been linear.