estimating true kwh

[David71201]

Two years ago I bought a used 2015 Model S 70 that had 147K miles on it. Before purchasing it, I remember asking what the range was (knowing that it was supposed to originally have 234 miles). I was hoping it wouldn't have lost more than about 10%.

Two years later, I realize that I was asking the wrong question. Some average 250 kWh/mile due to climate and efficient driving, while others average over 400 kWh/mile. What I should have asked was, "What is the kWh?"

What I have done is notice that when I drove it from 80% down to 20%, 33 kWh were used. If the percents are true measurements of my battery capacity, then I am effectively starting out with 33/0.6 = 55 kWh (representing a loss of a little over 20% from the original 70 kWh). But is the percent it is giving a true measurement?

Is this the best way to estimate my true available battery capacity?

(And wouldn't it be nice if Tesla would let us choose kWH rather than percent or miles.)

 

[Magnuss44]

Well since we never know the actual kWh state of the battery, then I think its hard to make that assumption. Especially since tesla doesnt let the car access the full 70kWh.

How do you know you uses 33kWh over that 60%?

 

[LoudMusic]

Well since we never know the actual kWh state of the battery, then I think its hard to make that assumption. Especially since tesla doesnt let the car access the full 70kWh.

How do you know you uses 33kWh over that 60%?

The trip odometer tells you kwh consumed since the start of the trip you're on, and since the last time you charged.

 

[ucmndd]

Two years later, I realize that I was asking the wrong question. Some average 250 kWh/mile due to climate and efficient driving, while others average over 400 kWh/mile.

The car’s displayed rated range does not change based on efficiency / driving habits. It’s your best available estimate of battery capacity as a percentage of new.

 

[Rocky_H]

I remember asking what the range was (knowing that it was supposed to originally have 234 miles). I was hoping it wouldn't have lost more than about 10%.

Two years later, I realize that I was asking the wrong question. Some average 250 kWh/mile due to climate and efficient driving, while others average over 400 kWh/mile. What I should have asked was, "What is the kWh?"

But that's the same thing, basically. As @ucmndd mentioned, that number isn't a Guess-O-Meter, like most other auto makers use. It is actually a reading of the kWh divided by a FIXED efficiency constant for that model. So that rated mile number is effectively a form of measurement of the quantity of energy, but converted in units from kWh into something that people can kind of picture. That conversion constant changes of course from model to model, because a Model 3 isn't going to have the same efficiency as a Model X. But within a certain model, you will be able to get a rough idea if the capacity of the battery is down based on whether that full rated miles number has gone down.

(Now there's a whole 'nother thing about the reading accuracy of the amount of energy has drifted and gotten inaccurate or not)