Understanding Supercharger rates

[Sknz]

We stopped and charged at Macedonia on Friday on our way to downtown Cleveland. We had 98 miles of range when starting the charge. The charge rate was 330 mph or more and 300 amps:

Today we stopped again and the charge rate would not go beyond 132 mph and 105 amps starting with 160 miles of range. When charging on Friday the charge rate was higher at 240 miles of charge than it ever got to today. We even moved the car to a different bay and same results. In any event we made it home with 10 miles of range remaining. Anybody have ideas on the different Supercharger rates we experienced? Thanks.

 

[deonb]

Are you familiar with curve? (Sounds like you are since you were mentioning it was higher at 240).


However, were there other cars at the SuperChargers on Friday?

If so, you're sharing the charge rate with other cars. You'll notice the SuperCharger ports are labelled:
1A 1B 2A 2B 3A 3B

etc.

Where 1A shares with 1B etc.

What you need to do is find a unique number-part. So if someone is in 1A and 2B, you should go to 3A or 3B.

 

[Sknz]

Good point…I did forget to mention that we were the only car at the site each time we charged. Thanks.

 

[Owner]

My supercharger posts may help you understand how they work and how I put them to the test with some answers from Tesla engineers.

Supercharger Time Test | Tesla Owner
Charger Test 4, 5 QA | Tesla Owner

 

[Cottonwood]

I've posted this elsewhere but it is relevant here. This plot is from using VisibleTesla to monitor a 120 kW supercharging session starting at 19 rated miles remaining and ending 80 minutes later at 268. The blue Rate of Charge curve is proportional to mph. The time integral of it, range, is in red.
View attachment 42716

I have seen this post of yours a few times on other threads, and the relationship of the "Rate of Charge" to the "Range" plots disturbed me. If the "Range" were the integral of "Rate of Charge," then it would still be rising at a very noticeable rate at the end of session. After all, at the end, "Rate of Charge" is at about 45% of its peak, but the slope (rate) of the "Range" plot is essentially flat (zero rate).

Then I realized the problem! The "Rate of Charge" as reported by the MS is the average rate during the session. To get the instantaneous "Rate of Charge," you need to look at "Power." I have found that "Power" divided by 300 Wh/mi* is very close to what the MS 85 reports for Supercharger rates and makes all the integrals work out.

Would you please provide this plot with "Power" also displayed? I hope that it is in kW; if VisibleTesla displays it in Watts, then never mind...

*300 Wh/mi is the factor for Supercharger, DC charging; for AC charging, it is higher because of the inefficiencies of the onboard, AC charger.

 

[Benjamin Brooks]

I have seen this post of yours a few times on other threads, and the relationship of the "Rate of Charge" to the "Range" plots disturbed me. If the "Range" were the integral of "Rate of Charge," then it would still be rising at a very noticeable rate at the end of session. After all, at the end, "Rate of Charge" is at about 45% of its peak, but the slope (rate) of the "Range" plot is essentially flat (zero rate).

Then I realized the problem! The "Rate of Charge" as reported by the MS is the average rate during the session. To get the instantaneous "Rate of Charge," you need to look at "Power." I have found that "Power" divided by 300 Wh/mi* is very close to what the MS 85 reports for Supercharger rates and makes all the integrals work out.

Would you please provide this plot with "Power" also displayed? I hope that it is in kW; if VisibleTesla displays it in Watts, then never mind...

*300 Wh/mi is the factor for Supercharger, DC charging; for AC charging, it is higher because of the inefficiencies of the onboard, AC charger.

+ 1

 

[wcalvin]

Thanks for that explanation of "mph" never going below half!

 

[wcalvin]

If you want to estimate charging time, given different starting points

OK, here is the curve to use if you want to estimate charging time, given different starting points.