Tesla’s Supercharging Math

[cruzinhk]

Does anyone has the same experience that Tesla always overcharges the supercharging fee?

For example, my car’s reading says 48.2 kWh is used since last charge so I thought it would cost me 48.2 X $0.28 (that’s the rate for this particular supercharger at Daly City CA) = $13.50 to charge up to the same level (90%).

It ended up $16.50 for the session. I noticed it every single time, just the matter of how much higher they overcharge. Tesla is disgusting.

 

[tjkessler]

There's energy loss in charging and supercharging often has to heat the battery as well. That's all electricity
that doesn't end up as charge.

 

[ajdelange]

That's a 22% discrepancy. When super charging there is no loss from conversion from A/C to DC and the portion of the charge energy that goes to warm the internal resistance of the battery is more like 6%.

 

[ewoodrick]

There's no loss converting from AC to DC? Then why is there so much heat coming from the inverter behind the wall? There definitely is loss.
And many of the car's numbers aren't as precise as you may think.

But since Tesla is definitely out to overcharge you, every thing I'm saying is probably moot

 

[ajdelange]

There's no loss converting from AC to DC? Then why is there so much heat coming from the inverter behind the wall? There definitely is loss.

Well of course there is but you are billed by the volts and amperes delivered to the car - not the VA delivered to the station transformer.

And many of the car's numbers aren't as precise as you may think.

Sorry, can't find the place in my post where I expressed an opinion as to the accuracy of the car's numbers.

But since Tesla is definitely out to overcharge you, every thing I'm saying is probably moot

If you think that then you probably do think they are charging you for excitation VARs too. The question then becomes how do they allocate those to the individual cars at the station.

 

[Krazaak]

It tells you how many kWh went into the car during charging, that's what you're billed for. I don't believe power used while the car is parked, for cabin overheat or sentry mode is factored into the kWh consumed in the trip meter.

 

[jimbo69ny]

I’ve been wondering about this a lot too. I have been doing a lot of testing but unfortunately I can’t really talk about it. I think Tesla collects a lot of data from multiple different points. The display in the car and the data that TeslaFi obtains is based on data from the battery BMS. NOT from the supercharger or any other point. So the display is showing actual power going into the power after losses.

 

[dethman]

car's reading of 'X kwh used since last charged' doesn't account for a lot of battery usage, such as when the car is parked and using sentry mode, when it's stopped and using the A/C, any preheating/precooling, and general crap tesla battery loss when idle.

 

[cruzinhk]

car's reading of 'X kwh used since last charged' doesn't account for a lot of battery usage, such as when the car is parked and using sentry mode, when it's stopped and using the A/C, any preheating/precooling, and general crap tesla battery loss when idle.

My X is 2016 with AP1 so no sentry mode.