Charging times

[Max*]

Again, specifying how many mph you get without specifying what car you're charging is futile. There's now 8 different rated miles.

I usually get 27 mph at 40/240, saw a 28 maybe once.

How is charging from a non-SpC different for various car models? What does the rated miles have to do with charge rate?

I thought the only place the car model (more specifically the voltage your battery can take due to the size of your battery) affects is charging at SpC.

 

[stevezzzz]

How is charging from a non-SpC different for various car models? What does the rated miles have to do with charge rate?

I thought the only place the car model (more specifically the voltage your battery can take due to the size of your battery) affects is charging at SpC.

The charge rate may not differ: it's determines by voltage and current. What differs is the amount of charge that equates to a Rated mile in the various models, so different variants of Model S/ModelX, all charging at the same charge rate, will add Rated miles at somewhat different rates.

Clear as mud, right? :biggrin:

 

[Fuma586]

How is charging from a non-SpC different for various car models? What does the rated miles have to do with charge rate?

I thought the only place the car model (more specifically the voltage your battery can take due to the size of your battery) affects is charging at SpC.

I believe your correct. Although I suspect a Tesla wall charger pulling 80A would slow down towards the very end of the cycle.

 

[AWDtsla]

How is charging from a non-SpC different for various car models? What does the rated miles have to do with charge rate?

I thought the only place the car model (more specifically the voltage your battery can take due to the size of your battery) affects is charging at SpC.

Charge rate in kW (for AC) under 90% should be the same for all cars. Somewhere after that there is a different taper.

However, when people quote charge rate in units of MPH, that's rated miles and thus different between different Model S's. My car is ~310 Wh/mi, whereas a 70D is somewhere around 260Wh/mi. You can either try and calculate it, or look at the energy analyzer and estimate where on the graph the "rated" line is.

 

[Max*]

The charge rate may not differ: it's determines by voltage and current. What differs is the amount of charge that equates to a Rated mile in the various models, so different variants of Model S/ModelX, all charging at the same charge rate, will add Rated miles at somewhat different rates.

Clear as mud, right? :biggrin:

Actually that is fairly clear.

So the rated mile calculation is based on the wh/mi the car uses, right? And the wh/mi varies by car, somewhere from 290 to 300 (or is there a greater deviation?). So that's about a 3.33% difference.

So at 29mph charge times, the delta between various models should be less than 1mph of charging. Yes, the models will vary, but by a very small amount (unless the deviation is greater above)

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Charge rate in kW (for AC) under 90% should be the same for all cars. Somewhere after that there is a different taper.

However, when people quote charge rate in units of MPH, that's rated miles and thus different between different Model S's. My car is ~310 Wh/mi, whereas a 70D is somewhere around 260Wh/mi. You can either try and calculate it, or look at the energy analyzer and estimate where on the graph the "rated" line is.

I think the 70D is closer to 290wh/mi rated, it's not 260.

 

[AWDtsla]

I think the 70D is closer to 290wh/mi rated, it's not 260.

290 doesn't work, that would mean they've reduced the anti-brick/0 reserve to 0.5kWh from 7kWh! Reducing the buffer would make sense but not by that much. I haven't been able to find a screenshot of the 70D energy analyzer to confirm, but it would be nice. In the 260's seems reasonable.

 

[Max*]

290 doesn't work, that would mean they've reduced the anti-brick/0 reserve to 0.5kWh from 7kWh! Reducing the buffer would make sense but not by that much. I haven't been able to find a screenshot of the 70D energy analyzer to confirm, but it would be nice. In the 260's seems reasonable.

Here's one I just took, it's hard to tell from the scale. The 300 line and the rated line are almost touching, but the rated is slightly below it.

I have gotten my "avg" (on the right) to match up with the "rated" line and it was either 290 or 288 or something very close to 290 (also the average projected then matches perfectly with rated, as you would expect).


I've only hit 260wh/mi a few times on road trips in the summer, and I'm fairly certain it's far below the "Rated" line.

I understand what you're saying about the math not working (70kwh (full capacity, even though we know it's closer to 65 I believe?) / 290wh/mi = 241miles which is the EPA rated amount), but I can assure you it's not 260. The only explanation is if Tesla screwed up the rated line, but I don't think so.

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Another way to look at it, the 328wh/mi average for the last 5 miles is 28wh/mi over 300. If we take that distance and go below 300 wh/mi that would put us at 272wh/mi, but as you can see the rated line is much closer to 300 than the distance between the rated and average.

There is no way the Tesla's consumption meter for rated miles is showing 260wh/mi.

 

[AWDtsla]

Here's one I just took, it's hard to tell from the scale. The 300 line and the rated line are almost touching, but the rated is slightly below it.

View attachment 108052


I have gotten my "avg" (on the right) to match up with the "rated" line and it was either 290 or 288 or something very close to 290 (also the average projected then matches perfectly with rated, as you would expect).


I've only hit 260wh/mi a few times on road trips in the summer, and I'm fairly certain it's far below the "Rated" line.

I understand what you're saying about the math not working (70kwh (full capacity, even though we know it's closer to 65 I believe?) / 290wh/mi = 241miles which is the EPA rated amount), but I can assure you it's not 260. The only explanation is if Tesla screwed up the rated line, but I don't think so.

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Another way to look at it, the 328wh/mi average for the last 5 miles is 28wh/mi over 300. If we take that distance and go below 300 wh/mi that would put us at 272wh/mi, but as you can see the rated line is much closer to 300 than the distance between the rated and average.

There is no way the Tesla's consumption meter for rated miles is showing 260wh/mi.

Interesting. So if that's what is displayed, then ~290 is probably what's used in the calculation. But I think Tesla is cooking something here to make the 70D not look as efficient as it is, probably to protect 90D sales. I have absolutely no hope of going under rated Wh/mi in my car, for example.

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...but even at 290, 70D will be ~7% higher MPH while charging than a P*D

 

[Max*]

Interesting. So if that's what is displayed, then ~290 is probably what's used in the calculation. But I think Tesla is cooking something here to make the 70D not look as efficient as it is, probably to protect 90D sales. I have absolutely no hope of going under rated Wh/mi in my car, for example.

You can't get rated miles even in the summer on a long distance trip?

My daily commute in the summer is about 330-350wh/mi, but I've taken the same trips both summer and winter (DC<-> NYC and DC<->Boston), summer I can get about 270-280wh/mi going 75mph (and I've seen 260 a few times when I hit traffic).

My daily commute in the winter is about 450-500wh/mi, but on that same roadtrip it was looking more like 330-350wh/mi at 75mph.

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...but even at 290, 70D will be ~7% higher MPH while charging than a P*D

Yep, so that's 2mph difference. That coupled with my 245V instead of 240V, explains why I see 31mph, while you see ~28.

I learned something new today. Thanks.

 

[AWDtsla]

You can't get rated miles even in the summer on a long distance trip?

My daily commute in the summer is about 330-350wh/mi, but I've taken the same trips both summer and winter (DC<-> NYC and DC<->Boston), summer I can get about 270-280wh/mi going 75mph (and I've seen 260 a few times when I hit traffic).

My daily commute in the winter is about 450-500wh/mi, but on that same roadtrip it was looking more like 330-350wh/mi at 75mph.

Haven't had the car long enough to try. But I have tried testing for efficiency by pre-heating and then driving with climate control off, it hasn't been a good picture so far, and that's already sucked all the joy out of driving a P90D. I'd literally have to be a road hazard to try and be more efficient.

 

[Cottonwood]

Actually that is fairly clear.

So the rated mile calculation is based on the wh/mi the car uses, right? And the wh/mi varies by car, somewhere from 290 to 300 (or is there a greater deviation?). So that's about a 3.33% difference.

So at 29mph charge times, the delta between various models should be less than 1mph of charging. Yes, the models will vary, but by a very small amount (unless the deviation is greater above)

I went through this is great detail with my Sig P95. Those numbers were approximately (within a percent or two):

• 290 Wh/mi — DC rated miles out of the battery.
• 300 Wh/mi — DC rated miles into the battery, this happens with a Supercharger or a CHAdeMO.
• 333 — AC Rated miles into the battery. This happens with AC charging.

If you you go through those numbers, DC charging is about 97% efficient, and the AC chargers are about 90% efficient in converting AC to DC.

All those numbers scale for the the specific model. Remember that rated miles come from the EPA tests, not reality. For example, my P85D gets about 305 Wh per DC rated miles out of the battery; it is about 5% less efficient per EPA standards than my Sig P85. In reality, with Range Mode on and motor sleep, it is almost as efficient as the Sig P85.

The best way to calibrate your specific car's Wh/rated mi is to start after a fresh charge with temps at 50-68˚ F., 10-20˚ C., the car stabilized at that temp, and drive a healthy distance without stopping (at least 100 road miles). Then look at the trip screen for the Wh/mi since the last charge. Take that number and scale it by actual miles driven divided by rated miles used. Do this a few times to make sure that your numbers are consistent. Another way to do this is to find a time on your trip after that healthy distance, that your miles driven equals your rated miles used; at that point the scaling factor is 1.00 and your can just read the Wh/mi from the trip screen.

When all is said and done, all this is an approximation modulated by heating and cooling during charging. Using the approximation of 3 rated miles per kiloWatt is pretty good. Use that as a guesstimate for charge time, but monitor the car for reality.

Have fun out there! :biggrin:

 

[AWDtsla]

If you you go through those numbers, DC charging is about 97% efficient, and the AC chargers are about 90% efficient in converting AC to DC.

I've been arriving at a consistent 93.5% efficiency at 40A. Drops to ~92% at 20A.