kW discrepancy between Ford Pass and receipt from Ford

[quisisana]

Brand new owner and charged yesterday at a Tesla Supercharger. Ford Pass stated I used 13 kWs during my session. I received an email receipt from Ford that stated I used 18.6 kWs. Anyone have an explanation?

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[Snakebitten]

One value is how much made it into the battery.
The other is how much made it out of the DCFC charger.

The difference between the two is the heat/energy-loss.

You can't transfer that energy at 100% efficiency.

 

[DeltaDelta]

Just a guess but probably difference between energy added to the battery and electrical energy consumed (charging a battery costs energy, so 1 unit of battery charge may cost 1.3 units of electrical energy)

 

[lifebythemile]

I'm not so sure on that... I was prepping for a long day of driving the other night and hit a Supercharger with 8% battery. Via Plug&Charge, the app showed 58kWh when I was at 99%*, was billed for 70kWh, and based on going from 8% to 100%* it should have been 66kWh. The extra 4kWh I can understand as electrical system loss, battery heating, etc. But really curious how the app came up with 58kWh...

*Disclaimer: Before people start posting "you should never DCFC to 100%" I'm fully aware of proper etiquette, time loss, etc. For my specific situation (and an empty supercharger station, 4 of 16 stalls in use), it worked out easier to have dinner while it went all the way to 100% rather than having to stop for 15min with 2 other scuba divers shivering cold^ while the car charges enough to get back home.
^only a slight exaggeration.

 

[DeltaDelta]

Charging in ideal conditions will get you 90-95% efficiency, so 5-10% of the energy is wasted. Remember, it costs energy to charge a battery. So to charge 9 units of energy you have to spend 10 units of energy.

Charging is more efficient at lower states of charge, so I'm not surprised at your 6% loss for 8%-90%, I am a bit surprised that it was that efficient all the way to 100% but I haven't really looked into the efficiency of fast chargers that thoroughly.

The 30% loss you describe in your original post seems somewhat high, but if you started in a higher state of charge and lower battery temperature it doesn't seem wild (as it would also be burning a lot of energy trying to warm up the battery to speed up the charge rate).

 

[Maquis]

One value is how much made it into the battery.
The other is how much made it out of the DCFC charger.

The difference between the two is the heat/energy-loss.

You can't transfer that energy at 100% efficiency.

It’s not “how much made it out of the DCFC”, it‘s the AC mains input to the DCFC. There are far more losses between the utility input and the DCFC output than there are between the DCFC output and the battery.
But you are correct, the difference is conversion and transfer losses Plus any energy used for battery and/or cabin heat.

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