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Energy used since last charge does not match true range

ACofNY

Member
Aug 25, 2019
52
17
Long Island, NY
We took a nice fall drive with my M3 SR+ that I bought last year. I started with 100% charge, with a range of 227 (max when new was 231, not 240mi.) It was cool out so I set the interior manual temperature to 65 deg with A/C off. I have Sentry mode on when away from home and parked for about 5 hours straight for a hike and maybe 1/2 additional. I took a local road for part of the trip home and got 190 watt/mi (since last charge) for the 165mi trip with 28% capacity at the end of the trip. I assume the Sentry uses 2 mi/hour. If the SR+ has about 60+ kWh, My rough calculation (and ABRP App) says that the battery capacity should be roughly 42-45%. I’ve done other local touring drive and got 165 watt/mi (in cool weather) with almost no highway. My highway drives reports 240-265 watts/mi. again not in extreme weather. That range is disappointing but matches the recently reported 85% efficiency, less than usable 190 mi est. range if I don’t run to 0% . It seems like 190 watts/mi gives me slightly more than 100% efficiency. I thought the 240mi range was based on 240 watts/mi. If I am getting 190, I expect closer to 300 mi range. What is wrong with my calculations?

I bought this M3 with the wrong impression that the range Tesla reports is accurate on normal conditions now I wished I got the longer range battery.

The EPA range should have local and highway ranges to help us decide when buying the car like ICE.
 

GtiMart

Member
Nov 13, 2019
979
820
Quebec City, Canada
I don't think the SR+ has a 60kWh pack. Search the forum, I think it's less than that.

Many many things affect consumption, thus range. Temperature, hilly vs at terrain, rain or snow, how your tires are inflated, if you carry extra weight, wind speed and direction, how agressive you drive. Then there is power usage while you don't drive, heating the car, the battery if you preheat, etc. EPA cannot handle all those variables. It's similar for ICE cars but no one checks because the cars don't report consumption and remaining range as precisely.
 

ACofNY

Member
Aug 25, 2019
52
17
Long Island, NY
All of our newer ICE cars reports MPG and range fairly accurately these days, within 1 MPG, and it adjusts it as the conditions change. The MPG for mixed and highway are either on, or slightly better. Most of our cars exceed the highway, as long as you are not averaging greater than 70MPH.

My main thing is the Tesla is reporting a much lower energy useable as expected for slower speed . I know my car is rated to use 245 watts/mile (mixed speed)* 240 miles = 58.8 KW (over part of a day to avoid phantom drain.) Why is it if I’m driving on a trip and it’s reporting much less usage, 58.8k / 190mi/ watt = 309mi I still don’t get the even close to the rated range range? I read that about 65mph you get 85% efficiency, using that, 58.8k *0.85 /190 = 263. It seems like the reported usage 32 KW and 190 w/mi does not include the 80% efficiency which seems what it is even at low speeds. When it says I used 34 kWh from 100% charge, my capacity is at 23%. The reported range must not be actual. I would think with Tesla’s great Sw, they should be much more accurate like I’ve was told / read before I brought mine. I know the usage does not include energy loss when parked. Some of the newer studies are now reporting efficiency for different car models.
 

ACofNY

Member
Aug 25, 2019
52
17
Long Island, NY
I don't think the SR+ has a 60kWh pack. Search the forum, I think it's less than that.

I did before I wrote it, it ranges from 60 to 62 kWh, although some sites states 55 kWh. (If it’s 55 kWh, the usage / mi must be 229 w/h. It still doesn’t work out. Must be only 80-85% efficiency regardless what they are reporting/publishing.
 
Last edited:

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
10,031
12,076
San Diego
I thought the 240mi range was based on 240 watts/mi.

No, it's not. You can check the Constants thread as recommended. The key numbers for a 2019 SR+ (it's not the same for a 2020!) are:

219Wh/rmi ("charging" constant, results using this number include the buffer)

~209Wh/rmi (BMS "constant")

~206Wh/rmi (trip meter "constant")

Your battery at 227 rated miles at 100% has capacity (INCLUDING the 4.5% buffer below 0 rated miles) of 227rmi*219Wh/rmi = 49.7kWh (It sounds like you started with a below average battery for sure - best not to take a car that starts with fewer than the published rated miles - it really matters! - but that is in the past...) Normal 2019 SR+s started at 240 rated miles, in excess of 52.5kWh (as high as 53-54kWh).

And to get 'parity' you need to get 206Wh/rmi or so on the trip meter to get "mile per rated mile" rolloff.

In your case:

165mi*190Wh/mi (trip) / 206Wh/rmi (trip) = 152 rated miles used while driving.

ended at 28% of 227, 64 rated miles. Presumably started at 100%, 227 rated miles???

So that's 227rmi - 64rmi = 163 rated miles.

So it looks like (assuming you started at 100%), the 5 hours of sentry (what about cabin overheat protection? was it on?) used 11 rated miles. That's a bit high - I'd expect closer to 7-8 rated miles for that duration - but again, overheat protection. Just a discrepancy of 3-4 miles.

It's easier to do these calculations if you make a note of your rated miles when you leave the car and when you get back to it, so you can eliminate that unknown.
Anyway, it all looks like it makes sense, within just a couple miles.

Check out the link above for the data for your car. Should make sense.


As a practical matter, after doing a few long drives, that as long as you can go 150-175 miles without stopping, you'll probably be fine for Supercharger usage. More range of course gives more flexibility (and a larger battery allows faster charging).

So you should be ok, for the most part.

But I would be concerned in NY in general that the winter will make it very difficult to do that.

Definitely owners purchasing a vehicle need to account for loss of capacity, and understand realistic consumption numbers. It's easy with those numbers to understand actual real world range.
 
Last edited:

ACofNY

Member
Aug 25, 2019
52
17
Long Island, NY
No, it's not. You can check the Constants thread as recommended. The key numbers for a 2019 SR+ (it's not the same for a 2020!) are:

219Wh/rmi ("charging" constant, results using this number include the buffer)

~209Wh/rmi (BMS "constant")

~206Wh/rmi (trip meter "constant")

Your battery at 227 rated miles at 100% has capacity (INCLUDING the 4.5% buffer below 0 rated miles) of 227rmi*219Wh/rmi = 49.7kWh (It sounds like you started with a below average battery for sure - best not to take a car that starts with fewer than the published rated miles - it really matters! - but that is in the past...) Normal 2019 SR+s started at 240 rated miles, in excess of 52.5kWh (as high as 53-54kWh).

...

Definitely owners purchasing a vehicle need to account for loss of capacity, and understand realistic consumption numbers. It's easy with those numbers to understand actual real world range.


Thanks a lot for your explanation!

Your calculations seems to work out, but I have to do more reading to get a better understanding. Few things:

When I purchased my M3 a year ago, I started with a 100% capacity range of 231 mi., I was told it is a calculated range and one does not expect to be guaranteed the 240mi. I lost 4 miles over a year. My co-worked who got a M3 a month earlier and stirred my interest in Tesla, has only 220 range now. (I barely drive unfortunately, I spend more energy keeping the battery charge since my commute is less than 2 mi.)

I need to read to understand the difference of the 3 different Wh/rmi you state above. Looking at the fuel economy .gov site, it states that my model is 25kw/100 mi. Which comes out to 60kw battery for 240 mi. That is probably why some sites states that the battery is 60kwh battery, this messed up my concept and calculations. The battery capacity I thought it was, is off; when i charge it 2 days later when the battery capacity was 21% remaining, my charge bill stated I used 25.29 kWh to charge it to 80%.

I wanted to see what is the most range I can get on this trip since the temperature and trip is the best I probably can get. From this, I will be disappointed on subsequent trips when I will be driving much faster and with the climate system on. The cabin overheat was off, but since it was in NY, I didn’t want to turn Sentry off.

Using your equation, I come out with 158mi range from 100% SOC to 20% for high speed highway driving with climate control on, etc, with the 260 w/mi displayed. When I purchased my M3, I thought I would be able to make our typical 180 mi direct trip to my family staying over the weekend with margin without charging. I was disappointed. For the family with a house, I now top off the battery just a few hours at 110v, but the others with apartment, I can’t. As I get more than halfway home, SC is not convenient. The long range would have been perfect. That is why our diesel car with a true range of 600mi on a tankful is more convenient. ☹️
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
10,031
12,076
San Diego
I was told it is a calculated range and one does not expect to be guaranteed the 240mi.

You were told that in error, as far as I can tell. I believe most new owners saw the full 240 rated miles, if only for a brief period. However, you're not the first that I've seen reporting less.

Looking at the fuel economy .gov site, it states that my model is 25kw/100 mi.

That's an AC kWh/mi value (what really matters for COST - wall to wheels). Not DC kWh/100mi, which is what matters for RANGE.

; when i charge it 2 days later when the battery capacity was 21% remaining, my charge bill stated I used 25.29 kWh to charge it to 80%.

Yeah, those are AC kWh. This doesn't quite check out; you added 59% of 227, or 134 rated miles.

That should be about 134rmi*209Wh/rmi / (0.9 DC Wh/ AC Wh) = 31.1kWh. Assuming 90% charging efficiency. Not sure what the discrepancy is though.

Can always check again just to be sure you have the right numbers.

When I purchased my M3, I thought I would be able to make our typical 180 mi direct trip to my family staying over the weekend with margin without charging. I was disappointed.

Yeah that's tough. You aren't the first one. It's important to understand how the energy works and what typical consumption is.

Using your equation, I come out with 158mi range from 100% SOC to 20% for high speed highway driving with climate control on, etc, with the 260 w/mi displayed.

I calculate 158mi*260Wh (displayed) /mi / 206 Wh (displayed) /rmi = 199 rated miles used. That's 88% of 227 rated miles. Not sure which equation you are using.

In order to make the trip to your family, 100% to 0%, you would need to do about:

227rmi*206Wh (displayed) /rmi / 180 mi = 260Wh/mi (displayed) This is approximate, but you can test and see for yourself how close it is.

So you CAN do it, but you have to be willing to take the car to 0%, or drive more slowly, or draft. And you most likely won't be able to do it in winter.

At this time of year, if you turn off AC & heat entirely, I think you probably have a pretty good shot at it.
 
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ACofNY

Member
Aug 25, 2019
52
17
Long Island, NY
You were told that in error, as far as I can tell. I believe most new owners saw the full 240 rated miles, if only for a brief period. However, you're not the first that I've seen reporting less.


That should be about 134rmi*209Wh/rmi / (0.9 DC Wh/ AC Wh) = 31.1kWh. Assuming 90% charging efficiency. Not sure what the discrepancy is though.

Looking at your figures, it sounds like something is not right with my information . I took a photo of the screen when I charged it. It shows I went 179.5 miles and used 34 kW/h, which does not include loss when parked and from Sentry, from full charge. What I might got wrong is the SOC at that point, it was 28% from the long trip plus additional 14 miles. My displayed was 194 rmi since my last charge. The 25.29 kWh charge is reported when charging it at work using Chargepoint. Something tells me ChargePoint is not correct. They charge by time anyhow.

I calculate 158mi*260Wh (displayed) /mi / 206 Wh (displayed) /rmi = 199 rated miles used. That's 88% of 227 rated miles. Not sure which equation you are using.

In order to make the trip to your family, 100% to 0%, you would need to do about:

227rmi*206Wh (displayed) /rmi / 180 mi = 260Wh/mi (displayed) This is approximate, but you can test and see for yourself how close it is.

So you CAN do it, but you have to be willing to take the car to 0%, or drive more slowly, or draft. And you most likely won't be able to do it in winter.

At this time of year, if you turn off AC & heat entirely, I think you probably have a pretty good shot at it.

I don’t like to run the car to 0%. I made the trip back in the summer using very little energy with no A/C in August because my A/C condenser cracked from hard acceleration.

What I found about EV vs ICE is if I hit major traffic with the ICE, I use more fuel while the M3 uses less except in the winter.

I am using 227rmi *0.80 *206 Wh / rmi / 260 Wh/mi = 143.9. Yup I calculated it wrong. An it’s worse than I previously calculated ☹️

All your information is right on! Thanks.
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
10,031
12,076
San Diego
It shows I went 179.5 miles and used 34 kW/h, which does not include loss when parked and from Sentry, from full charge. What I might got wrong is the SOC at that point, it was 28% from the long trip plus additional 14 miles. My displayed was 194 rmi since my last charge. The 25.29 kWh charge is reported when charging it at work using Chargepoint. Something tells me ChargePoint is not correct. They charge by time anyhow.

There is a lot of ambiguity here. If you charged from 28% to 80% then my calculation would be closer to what ChargePoint says.

ChargePoint energy numbers are usually pretty close, in my experience. (But not the “miles added” that they quote.)

In any case, with the full details on what your start SoC was and what you charged to, we can calculate the energy it should have taken, if you have interest. Just need the precise starting and ending point of the charge.

Charging from 28% to 80% should be about:

0.52*227rmi*209Wh/rmi/0.9 = 27.4kWh. That is closer. Maybe the ChargePoint is more efficient than 90% but it is not 97% efficient.

Ideally you quote starting and ending rated miles, not %, since it is more accurate.
 
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ACofNY

Member
Aug 25, 2019
52
17
Long Island, NY
I didn’t get the %SOC but do have the range remaining from a screen capture. (28% was before an additional 14 mi. trip.)
Here is what the screen had when I plugged the car in: from 100% - 227 mi. To ?% SOC with 48 mi remaining. (48/227= 21.1%) From last charge 179.5, 34 kWh, 192 Wh/mi, Consumption: 57 mi projected from last 30 mi/ 182 avg. 181 mi. Range at the end of charging to 80%.

The ChargePoint App states “25.29 kWh added”, I assume to the battery, not AC used to charge the battery.
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
10,031
12,076
San Diego
I didn’t get the %SOC but do have the range remaining from a screen capture. (28% was before an additional 14 mi. trip.)
Here is what the screen had when I plugged the car in: from 100% - 227 mi. To ?% SOC with 48 mi remaining. (48/227= 21.1%) From last charge 179.5, 34 kWh, 192 Wh/mi, Consumption: 57 mi projected from last 30 mi/ 182 avg. 181 mi. Range at the end of charging to 80%.

The ChargePoint App states “25.29 kWh added”, I assume to the battery, not AC used to charge the battery.

Yeah something does not compute here. Try again sometime and log the starting and ending point of the charge in miles, and take a picture of the ChargePoint app.

The ChargePoint app logs AC kWh since that is what you pay for.

I would expect for 134 rated miles added that ChargePoint should say about:

209Wh/rmi*134rmi/0.9 = 31kWh.

Since it said 25.29kWh, I would guess you added:

25.29kWh*0.89/209Wh/rmi = 109rmi.

That would take you to 70% SoC from 21%.

But anyway, just try again and log more data. Maybe there is something bad about the prior data.

——

For example, on March 12th I added 132.5 rmi to my 3P+ at a 6kW CP according to Stats. ChargePoint says it was 35.07 AC kWh (correct) with 147 miles added (always wrong, though maybe because at that time they did not allow trim selection - they do now, no idea if it addresses the scaling problem). I did not preheat the car to my knowledge when it was charging (would underestimate the efficiency numbers if I did)

With the 234Wh/rmi constant for the 3P+:

234Wh/rmi*132.5rmi = 31kWh DC

So efficiency is 31kWh DC / 35.1kWh AC = 88%.

Which seems about right based on what we know, for 6kW charging.
 

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