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How many MPH on 120V @ 12A and 16A?

AWDtsla

Active Member
Mar 3, 2013
4,266
3,960
NE
We know the Model 3 should charge miles about 30% faster than S due to efficiency, but we don't know if Tesla has managed to improve the large overhead while charging that leads to slow charging being very inefficient. Does anyone have real data on this, preferably captured with any logger other than the Tesla mobile app?

My napkin math says [email protected] should be 5.75 MPH, including overheads
 
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KJD

Supporting Member
Dec 14, 2013
1,351
1,009
SLC, UT
The Tesla doc says your number is a bit high. It looks to be more like 4 mph on this page.
Screen Shot 2018-05-30 at 9.14.23 AM.png


I think this is a good example of why you want to use 240 volts instead of 120 volts for charging.

Screen Shot 2018-05-30 at 9.16.49 AM.png


More details are here.
Home Charging Installation
 

Skotty

2014 S P85 | 2020 3 P19"
Jun 27, 2013
2,470
1,781
Kansas City, MO
The Tesla doc says your number is a bit high. It looks to be more like 4 mph on this page.
View attachment 304912

I think this is a good example of why you want to use 240 volts instead of 120 volts for charging.

View attachment 304913

More details are here.
Home Charging Installation

This chart can be a little misleading. Take note that all rows are for 240v, even though some of the amps listed would be far more common at 120v (a model 3 will only charge 5.5 miles per hour on a standard 120v 15 amp outlet with charging at 12 amp).
 

AWDtsla

Active Member
Mar 3, 2013
4,266
3,960
NE
The Tesla doc says your number is a bit high. It looks to be more like 4 mph on this page.
View attachment 304912

I think this is a good example of why you want to use 240 volts instead of 120 volts for charging.

View attachment 304913

More details are here.
Home Charging Installation

Thanks for the RTFM response, but those docs are inaccurate, if nothing else other than they lack precision. S75D would be almost 10% faster than P90D, depending on conditions. Just for one example.

Real world data please.
 

quantumslip

Member
Mar 3, 2015
483
517
Earth
Could someone retest but set to use kilometers? That would have better resolution and possibly provide a better idea of charging efficiency. Otherwise, a watt meter and other data could be used.
 

AWDtsla

Active Member
Mar 3, 2013
4,266
3,960
NE
Could someone retest but set to use kilometers? That would have better resolution and possibly provide a better idea of charging efficiency. Otherwise, a watt meter and other data could be used.

You get precision down to tenths of a mile using the API. Watt meter doesn't tell you what the internal losses are, therefore you can extrapolate nothing about the actual charging rate.
 
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quantumslip

Member
Mar 3, 2015
483
517
Earth
You get precision down to tenths of a mile using the API. Watt meter doesn't tell you what the internal losses are, therefore you can extrapolate nothing about the actual charging rate.

didn't know the api had that resolution; if one only could use the car display the km would be your best bet.

i guess watt meter would be useful if the amperage is rounded, but that is more of a rounding issue at that point
 

GregRF

Squirrel Power
Jul 22, 2014
521
1,044
CA
We know the Model 3 should charge miles about 30% faster than S due to efficiency, but we don't know if Tesla has managed to improve the large overhead while charging that leads to slow charging being very inefficient. Does anyone have real data on this, preferably captured with any logger other than the Tesla mobile app?

My napkin math says [email protected] should be 5.75 MPH, including overheads

According to TelsFi I was getting ~4.25mph on 12A. States around 72% efficient.

Since I upgraded to 240V I've been getting ~30mph @ 32 amps and 90% efficient.

Here are a few of the longer charges on 120V:
upload_2018-5-30_10-29-12.png


And my longest charge so far with 240V:
upload_2018-5-30_10-31-5.png
 

jsmay311

Active Member
Apr 22, 2016
1,141
1,667
Chicago suburbs
According to TelsFi I was getting ~4.25mph on 12A. States around 72% efficient.

Since I upgraded to 240V I've been getting ~30mph @ 32 amps and 90% efficient.

Wow. That's a huge difference.

Other studies I've seen comparing 120V and 240V charging efficiencies on Volts and Leafs have found much smaller efficiency penalties for using 120V instead of 240V... like only 2%-5% lower. (Excluding short-duration low-kWh charges, which show higher differences).
A comparison of electric vehicle Level 1 and Level 2 charging efficiency - IEEE Conference Publication
https://www.veic.org/documents/defa...el-2-electric-vehicle-charging-efficiency.pdf

The only explanation for this that I can think of would be if Model 3s / Teslas have much higher parasitic loads during charging than other EVs/Volts/Leafs(?). (Maybe the bigger battery could play some role in this as it would require more energy to initially heat/cool the larger pack to some target temperature for charging, but I wouldn't think the differences would be so dramatic unless it was charging in extreme temps.)
 
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AWDtsla

Active Member
Mar 3, 2013
4,266
3,960
NE
The only explanation for this that I can think of would be if Model 3s / Teslas have much higher parasitic loads during charging than other EVs/Volts/Leafs(?).

It does, this is a main problem. It's not charger efficiency. This also means solar panels on the car are out of the question, because anything below ~300W won't even make it to the battery, you'll actually end up with a negative charge rate.
 

GregRF

Squirrel Power
Jul 22, 2014
521
1,044
CA
but I wouldn't think the differences would be so dramatic unless it was charging in extreme temps.

Most of this charging would be taking place in 50-60 F ambient outdoor temps, so the parasitic losses shouldn't be due to temperature extremes.
 

CWFLY

Member
May 9, 2018
65
55
San Diego
FWIW, I charged my car last night via 120V/15A, which gave me roughly 110V at 12A. MPH fluctuated between 3 and 4.

Two questions:

1. Does anybody know what constant Tesla uses to convert Miles to kWh?
???? 310 mi / 75 kWh ????​

2. How does the UMC know the difference between 15A and 20A for 120v? I know the 20A has a little bend in the tab, but is there some sort of logic/code built into the adapter? (probably answered my own question)
 

AWDtsla

Active Member
Mar 3, 2013
4,266
3,960
NE
FWIW, I charged my car last night via 120V/15A, which gave me roughly 110V at 12A. MPH fluctuated between 3 and 4.

Two questions:

1. Does anybody know what constant Tesla uses to convert Miles to kWh?
???? 310 mi / 75 kWh ????​
One of you brave early adopters can figure that out, and I'd really like to know. Get data from your car via API. Remote S app or teslafi will work for this. Enable high precision, and note "Rated Miles" before starting charge. Finish a long charge, then note "Energy Added" and ending "Rated Miles". Do this *immediately* after finishing charge, it may not be valid even minutes later.

Energy added/(End-Start) = Rated Wh/mi.

Repeat the experiment to confirm. You should get a number with very high consistency.

2. How does the UMC know the difference between 15A and 20A for 120v? I know the 20A has a little bend in the tab, but is there some sort of logic/code built into the adapter? (probably answered my own question)
Yes.
 
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eladts

Member
Jul 31, 2016
784
1,073
Brookline, MA
2. How does the UMC know the difference between 15A and 20A for 120v? I know the 20A has a little bend in the tab, but is there some sort of logic/code built into the adapter? (probably answered my own question)

In order to charge at 120V/16A you have to use the optional 5-20 adapter for the UMC. This adapter will not physically fit to 5-15 sockets, as the neutral blade is rotated. If you use the standard 5-15 adapter there is no way for the UMC to know that this is a 20A circuit.
 

timk225

Active Member
Mar 24, 2016
2,047
1,059
Pittsburgh
My 3 consistently shows 5 mph on both the in car screen and on the phone app when charging at 118-119 volts and 12 amps. This could really be anywhere from 4.50 to 5.49 mph due to rounding. I don't always charge on a 5-15, but I've done it to try it out a few times.

My 14-50 plug charges at 31 mph on 243-244 volts and 32 amps.

I'm installing a 6-20 this week to charge the car when it's too much hassle to get the 15 foot 14-50 extension cord out and unplug the oven. My Tesla mobile connector adapter is on the way now.
 

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