The car's dashboard does NOT show the TOTAL consumption of the energy that entered the battery!
This is a bold statement, but also a very verifiable one.
For 1 month, after each daily drive,
For every single daily drive, I needed to add more kWh to the battery (refilling it to 70%), than what the car said were the kWh consumed in the previous day.
To be perfectly clear: I’m not talking charging efficiency. Only the “in” and “out” of the battery. You can read more about that in this other thread.
The plotted data shows a very interesting pattern:
I don’t know the definitive explanation for this, but:
I’m creating this topic:
That being said, I love my Model S. I really think it’s the best car in the world and wouldn’t change it for anything (besides a P100D!)
This is a bold statement, but also a very verifiable one.
For 1 month, after each daily drive,
- I took note of the kWh used, reported in the car's dashboard (Model S 85D)
- I charged every night to exactly 70%, to top of that day's consumption,
- After the charge, I took note of the kWh added to the battery (you can get that number from the car’s dashboard after charge completion, or from the car’s API).
For every single daily drive, I needed to add more kWh to the battery (refilling it to 70%), than what the car said were the kWh consumed in the previous day.
To be perfectly clear: I’m not talking charging efficiency. Only the “in” and “out” of the battery. You can read more about that in this other thread.
The plotted data shows a very interesting pattern:
- If you drive gently (~160 Wh/km), for each 50 kWh the car says you used, you can actually re-add around 52 kWh to the battery (~96% usage accuracy).
- If you drive like a maniac (~280 Wh/km), for each 50 kWh the car says you used, you can actually re-add around 59 kWh to the battery (~84% usage accuracy).
I don’t know the definitive explanation for this, but:
- It’s crystal clear that you can add more energy to the battery of the Model S, than the energy the Model S says is leaving the battery… and that can’t be right!
- Because the energy entering the battery is coherent with the expected charging efficiency (see this thread), I can only conclude that the Model S is not reporting the TOTAL energy leaving the battery
- Looking at the pattern of the graph above, my speculation / suspicion, is that the Model S is NOT measuring the battery’s discharge (in)efficiency:
- If you discharge a lithium (or any other) battery at a high C-rate, you won’t be able to achieve its rated energy capacity. For example, you’ll have energy being wasted to heat;
I’m creating this topic:
- To hear if you can replicate the experience (charge to X%, drive, take note of the kWh used during that drive, charge to the same X%, take not of the kWh added to the battery and see if it matches)
- Hear your other possible explanations for this.
That being said, I love my Model S. I really think it’s the best car in the world and wouldn’t change it for anything (besides a P100D!)