Supercharging costs discrepancies (Display vs Bill from Tesla)

[wycolo]

Chargepoint et al don't deliver the massive amperage that a SC does. Therefore TM has to deal with significant voltage drop going to the car's socket. You'd think they would have added a voltage sense wire to the SC plug so regardless whether the cable was water cooled or not they could still get correct KWHs delivered to the plug and bill accordingly. The amps are the same at any point in the cable all the way from charger units to plug, btw. On the other hand perhaps TM has given the task over to the car to determine usage so that the 'one mile up, 3 mile down' computation is used [Caution, your mileage may vary]. . . . my $0.02.
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[AWDtsla]

Chargepoint et al don't deliver the massive amperage that a SC does. Therefore TM has to deal with significant voltage drop going to the car's socket.

Chargepoint can't even give their installers adequate instructions. Every Chargepoint I've ever been at drops voltage a minimum of 6% and upwards of 8%. Of course charge circuit protection kicks in often enough and slows down the charge from the car side. As if the charge wasn't dogs*** slow enough, it gets even slower. Let's not even get into what happens on their shared power stalls.

You'd think they would have added a voltage sense wire to the SC plug so regardless whether the cable was water cooled or not they could still get correct KWHs delivered to the plug and bill accordingly. The amps are the same at any point in the cable all the way from charger units to plug, btw. On the other hand perhaps TM has given the task over to the car to determine usage so that the 'one mile up, 3 mile down' computation is used [Caution, your mileage may vary]. . . . my $0.02.
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Watercooling does nothing for I^2R losses, it just keeps the cable from catching fire. You guys should consider yourselves lucky anyway, since Tesla doesn't appear to be trying to add any charging efficiency or line losses. You're getting an extra 10+% energy for free, even when it meters "correctly".

 

[wycolo]

If water cooling is added to the otherwise same cable then 'I squared R' losses could be reduced, but if they took this opportunity to cheap out on the mod by shaving Cu content then, well, (never mind) . . .
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[mongo]

If water cooling is added to the otherwise same cable then 'I squared R' losses could be reduced, but if they took this opportunity to cheap out on the mod by shaving Cu content then, well, (never mind) . . .
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Are you referring the positive temperature coefficient of copper/ aluminum?

 

[wycolo]

> Are you referring the positive temperature coefficient of copper/ aluminum? [mongo]

Why, yes!
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[FalconFour]

So, about the cost discrepancy between the car and the station...
... and the lack of pricing information shown on the map/SC details bubble...
... and the lack of history available in the app, and having to dig through a fairly well-hidden part of the Tesla site to get history...

 

[Jedi2155]

The biggest issue I see here is that they advertise one rate on your vehicle by displaying the cost to charge making you think you spent $xx, while on the other hand they bill you usually a higher value on the actual. This is a serious customer issue that they should get taken care of right away because its asking for trouble.

 

[AWDtsla]

> Are you referring the positive temperature coefficient of copper/ aluminum? [mongo]

Why, yes!
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You can do that math, it's not going to be relevant for copper cable that can be handled by humans. What's the best average delta, 20C? Over 6 feet of cable?

 

[swaltner]

I did a road trip last week. Most charging sessions matched up almost exactly. Some were really far off ($0.20 displayed instead of $4.80 in reality). For the ones that had large discrepancies like this, I think I triggered it by leaving the charging screen in the Model 3 and playing with the navigation destination while the car was Supercharging. Not an excuse, but one item that I did which seemed to trigger these large discrepancies between the UI and reality.

 

[Reid]

First supercharge was for only $3 or something, I was testing it out and the car was not properly linked to my account, so I guess it was "free". I, too, was wondering where on earth I was supposed to see my billing, because nothing was showing up on my Tesla account.

Supercharged on Saturday and now I see the history tab.

So, if you don't have a history tab, keep enjoying the free supercharges and don't worry about what it SHOULD have cost you

 

[davewill]

Chargepoint can't even give their installers adequate instructions. Every Chargepoint I've ever been at drops voltage a minimum of 6% and upwards of 8%. Of course charge circuit protection kicks in often enough and slows down the charge from the car side. As if the charge wasn't dogs*** slow enough, it gets even slower. Let's not even get into what happens on their shared power stalls.

...

Sorry, I've got to put that one on Tesla. No other car drops their charge rate in those scenarios. The car is the one in error in this case.

 

[AWDtsla]

Sorry, I've got to put that one on Tesla. No other car drops their charge rate in those scenarios. The car is the one in error in this case.

1. The other cars charge slow as s***
2. Even if Tesla didn't drop the rate, that's still going to be 8-10% slower charging due to power lost to heat.
3. Tesla is trying to make sure you don't set your house on fire, although they need an override button.

 

[jsmay311]

Has tesla publicly addressed/explained these Supercharging billing discrepancies yet?


My supercharging usage/billing history is as follows:

1. North Aurora, IL
Screen: $0.92 (4 kWh)
Billed: Nothing
(This was 2 weeks after my purchase, and I believe it’s not unusual to not to get charged for your first charge or during the first few weeks of ownership.)

2. Coralville, IA
Screen: $8.40
Billed: $8.50 (Billed for 1 extra minute @ $0.10/min.)

3. Coralville, IA
Screen: $10.10
Billed: $10.20 (Billed for 1 extra minute @ $0.10/min.)

4. Normal, IL
Screen: $2.88 (12 kWh)
Billed: Nothing

5. Normal, IL
Screen: $1.92 (8 kWh)
Billed: $1.92 (8 kWh)

6. Normal, IL
Screen: $8.16 (34 kWh)
Billed: $8.64 (36 kWh)

 

[tivoboy]

I have seen this get MUCH better in the past few weeks/months. I just did a 1200 mile road trip and the billing presented on the model 3 screen in real time, and the total amount billed was accurate on the screen immediately after stopping and compared to the final billed amount in my account history. So, this part has gotten better.

I think if you are NOT billed, that is a station by station issue. Count yourself lucky in those cases. As for the HIGHER KW amounts, I think that as has been discussed, what comes OUT of the SC and what goes INTO the car are going to be different due to charging efficiency but Tesla is still going to be charging you the OUT of the SC amount in kWh, and a corresponding kWh rate. As for the minute overages, that is probably just a rounding issue. Sadly, we probably have no way of knowing when the minutes actually started.

It's at least NOWHERE near as bad as it was, with the in car display showing numbers that were GROSSLY different than the actual billed amount - which was always higher and probably actually more accurate. I wonder if one of the third party apps will tell me exactly HOW many kWh the car took in during a charge session, to compare to what Tesla says came out of the SC during that session?