Considering charge losses, heating and vampire drain, what is the true Wh/mile?

[J0hn.r]

So, Tesla updates Supercharger billing to add cost of electricity use for other than charging - Electrek

I already have seen a post on Facebook with somebody being charged for 65kWh while adding 56kWh, which is about 16% extra cost. That prompted me to revise my calculations of Wh consumption per mile:

SuC: added 438kWh, plus let's say 10% for charging inefficiencies and heating while charging, becomes 481kWh
Home charging: TeslaFi already presents two values, kWh Added = 444.84 and kWh Used = 506.52, which again is 13.87%

So while in TeslaFi Drive Summary it looks like I used 676.7 kWh to drive 1950 miles, at 347 Wh/mile, in reality I have driven 1998 miles and have a estimated range of 91, and used in total 988 kWh, averaging 472.9 Wh/mile which is a whopping 36.28% more than what the TeslaFi and the car average tells me.

Obviously it depends massively on how everybody uses the car, besides temperature and driving stile, it's now about how many times you used preheating, the sentry mode and refreshed the Tesla app.

 

[LukeT]

My teslafi reports different efficiencies by charge current on ac. I reckon c. 85% for 10-16a 3 pin/commando, 90-92% at 32a. Maybe 92-94% on a 3 phase charge point. These are then further reduced if I use any HVAC and are lower for very short charges (which I've ignored here - their numbers are all over place but they should account for a small minority of kwh).

If I assume 15% losses in all my supercharger use then adding up all kWh used and dividing by miles I get to a gross 463Wh/mile over 13k miles in my Model S. Also about 30% over car reported number.

Would high current dc be less efficient than home charging? I don't know. Your reported 16% says it is.

 

[Jason71]

I have not studied it in detail but I think I am getting about 90% efficiency from my 32amp Rolec.
what I would love to know is the efficiency of 3rd party DC chargers. Pretty sure they all charge by the KW of AC consumed so you are paying for the losses in their transformer and cables. So the worse they are the more money they make. Sooner or later this will have to be addressed. The same way petrol stations are checked for the accuracy of fuel delivery DC charging stations will need a minimum efficiency law and will have to be monitored.
Based on the discussions of the new law in California I am led to believe that their is currently no suitable technology for metering the DC rather than the AC in a charger. I am surprised and its a shame since if the seller suffered the transformer losses they would have an incentive to improve.
I wondered about starting a thread where people could report the KWs charged vs added to battery so we could see it anyone out there is particularly good or bad. there are a lot of variables though like. Temperature, SoC, HVAC so not sure if it would work.

 

[MrBadger]

I found what Instavolt DC '50kW' charged me kWh vs what car/TeslaFi reported for that charge to be very different.

eg
Instavolt charged for 15.329kWh vs

kWh added a rather strange figure, ie added > used/consumed hence >100% charge efficiency.

An ICE comparable top-up at £5.37 (0.35p/kWh) for 18%/50 odd miles range ~ 10p/mile in 19 minutes

Compare that to a similar supercharge 23%/70 miles ~ 6p mile in 12 minutes.

 

[LukeT]

Tesla Adjusts Supercharging Cost To Include Vehicle Use While Charging - Tesla Motors Club

Implication here is that the extra to be charged (Tesla, not thrid party) is not so much for their inefficiency as our playing of computer games in the warm. Devil's in the detail of course!

I read this that Tesla will still charge based on some analysis in the car on kWh taken in, rather than upstream AC meter at the supercharger.

 

[tsh2]

I don't see massive heatsinking on superchargers, so I assume they are reasonably efficient (90%+). But I assume what will be charged for is energy provided to the car - so HVAC and pre-heating will be the extra cost items (and this is in line with 3rd party rapid charging).

 

[Mr Miserable]

Aren't there regulations here in the UK covering the supply of electricity and the metering thereof?
I don't see Weights & Measures going out and testing Superchargers like they do with petrol pumps - perhaps they should.