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Discussion Starter · #1 · (Edited)
Further edited to fix my horrendous unit error. :rolleyes:
Edited to add what I've got my EVSE limited to.

After tracking my car for a while, I've finally got what appears to be some semi-stable real-world energy consumption that includes losses from charging.

We've all looked at the miles/kWh figure on the vehicle info screens, but there are inevitable losses from resistance in the charging cable and heat generated in the batteries from charging them. Cooling those warmed up batteries also uses some energy. So, I wanted to figure out just how much electricity does this car actually use?

The short answer: my vehicle info screen shows a lifetime usage of 3.6 miles/kWh. However, if I measure electricity used by my EVSE unit and divide by miles driven, I get somewhere in the range of 3.3 to 3.4 miles/kWh. The end result is a loss of between 0.2 and 0.3 miles/kWh driven to what I'll call "EVSE and charging losses." So, I'm losing about 5.6-8.3% to charging inefficiencies.

I think it's important to note that I've got my EVSE set to a max of 32A, quite a bit slower than the car can take or even what the EVSE can do. That's in an effort to limit some of these losses as well as take care of the battery.

This is in moderate to very warm outside temperatures. Perhaps 25% of the miles were with lows in the 60F range, and highs near 75-80F. The balance is more of a summertime in the south, with lows in the 70-80F range with highs between 90 and 98F. I drive the majority of my miles in a semi-urban environment; 35-45MPH speed limits with 1-3 miles between lights and stop signs. Maybe 20% of my miles are highway at 65-70MPH in moderate traffic. I make liberal use of pre-cooling the cabin and running the AC while I'm in a store. I didn't buy an EV so I could walk out to a hot car. I keep my car's cabin set between 74 and 76F, with recirculate on. Yes, I have to select recirc on every time. I've found that on hot days over about 80F the car does better at cabin temp control if I also select "sync" on the HVAC screen to get air out of all of the vents...which is another three presses. I wish I could just have that stay how I want it, but that's a topic for another very long thread!

Here's how I did this, problems, etc.:
  • I've got a "dumb" EVSE, it's a Grizzl-E charger. Not the smart version, but I do have the upgraded cable.
  • I don't have any way to directly meter what's going into the EVSE. I'm not too cheap to install a dedicated meter, I'm "value conscious."
  • My electricity provider recently began allowing for hourly reporting of electricity usage by my house, which facilitated this little experiment. It's pretty simple: I only charge at home, I always plug in after 9PM when the house no longer has solar loading so the HVAC isn't running too much.
  • So...check the miles on the car, and do some simple math. Easy-peasy!
There are a few issues with accuracy:

The big one is I have to guess at what the "rest of the house" is using when I'm charging the car. By waiting until after 8 or 9PM, my house is usually only drawing 1kWh/hour at that time, occasionally zero. They don't have anything more granular than 1 kWh increments unfortunately. I don't charge every night, so I do get some baseline info. Of course even that's not terribly accurate because of rounding. But, over enough time, I figure the rounding will smooth out and I'll get more accurate numbers. It's close enough.

Another issue is I really don't have a terribly large sample size. This is only over 500 miles or so and initial numbers were all over the map. I've waited for things to smooth out a bit; I'm now wobbling in a range from 3.27 to 3.43 miles/kWh.

I'm in the temperature sweet spot for EV usage. 70-90F is where EVs really shine for efficiency. However, I'm hopeful that this display of "EVSE losses" if you will translates smoothly to colder weather. Have to wait a while for that test.

Finally, I do wish I had a dedicated meter for my EVSE. Maybe someday, but I've spent so much on this car already I'm having a hard time justifying that expense. Perhaps those with smart EVSEs can chime in?
 

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Interesting, from the standpoint your efficiency calculations are considerably better than the oft-quoted figures of mid-80s for Level 2 and mid-70s for Level 1.

My own efficiency calculations have always been based on the rated current of the EVSE, so not really useful without making assumptions.

Id like to get hold of a RMS clamp to measure current. My plug-in Kill-A-Watt meter is only good to 15 amps. I see a BIG apparent efficiency difference between L1 12 amp and 16 amp I'd like to investigate. I'd also like to test L1 vs L2 efficiency at 16 amps, and L2 16A vs. 40A.
 

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Interesting, from the standpoint your efficiency calculations are considerably better than the oft-quoted figures of mid-80s for Level 2 and mid-70s for Level 1.

My own efficiency calculations have always been based on the rated current of the EVSE, so not really useful without making assumptions.

Id like to get hold of a RMS clamp to measure current. My plug-in Kill-A-Watt meter is only good to 15 amps. I see a BIG apparent efficiency difference between L1 12 amp and 16 amp I'd like to investigate. I'd also like to test L1 vs L2 efficiency at 16 amps, and L2 16A vs. 40A.
After 5000 miles our lifetime is 3.4 this is with several freeway trips and trips to Vegas
 

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Discussion Starter · #4 ·
Interesting, from the standpoint your efficiency calculations are considerably better than the oft-quoted figures of mid-80s for Level 2 and mid-70s for Level 1.

Id like to get hold of a RMS clamp to measure current. My plug-in Kill-A-Watt meter is only good to 15 amps. I see a BIG apparent efficiency difference between L1 12 amp and 16 amp I'd like to investigate. I'd also like to test L1 vs L2 efficiency at 16 amps, and L2 16A vs. 40A.
I edited my original post to include that I've limited my EVSE to 32A in part as an effort to limit some of these losses.

I've seen quite a few meters that use an RMS clamp and they're not terribly expensive. But even as easy as they look to install, I'm not confident in my ability to play with that much juice. If I'm going to have someone come out and install something, I'll just have a "real" in-line meter installed. They really don't seem to cost that much more.
 

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I edited my original post to include that I've limited my EVSE to 32A in part as an effort to limit some of these losses.

I've seen quite a few meters that use an RMS clamp and they're not terribly expensive. But even as easy as they look to install, I'm not confident in my ability to play with that much juice. If I'm going to have someone come out and install something, I'll just have a "real" in-line meter installed. They really don't seem to cost that much more.
I just need a handheld one for the tool bag. Too many occasions where I want to quickly check current -- not monitor it continuously, but I guess that feature would be bonus.

But I'll give you an example. This is what I've observed Level 1 charging on my other car (28kWh useable battery):
12 amp OEM EVSE = 25% gain over 8 hours
16 amp aftermarket = 40% over 8 hours
12 -> 16 is a 33% increase in amperage
25 -> 40 is a 63% increase in kWh
25% of 28kWh = 7kWh; 40% = 11kWh
120v x 12A x 8 hrs = 11.5kWh = 60% efficiency
120v x 16A x 8 hrs = 15.3kWh = 72% efficiency

...so I want to check that the labeled currents on the tags on each unit are what is being drawn in reality, because those efficiency differences are pretty stark (and also help explain why I can happily exist with 16A L1 charging with that car, but am miserable at 12A).
 

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Isint bulk of the losses in the ac to dc conversion into the battery and dc to ac conversion into the motor.
 

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Bubbajet, is your decimal place correct? 3.6 kWh/mile translates to about 40 cents/mile where I live (Portland, OR metro area, with electricity cost about 11 cents/kWh). The EPA ratings for EVs are usually in the range of 25-35 kWh/100 miles, which is 0.25-0.35 kWh/mile.
 

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Bubbajet, is your decimal place correct? 3.6 kWh/mile translates to about 40 cents/mile where I live (Portland, OR metro area, with electricity cost about 11 cents/kWh). The EPA ratings for EVs are usually in the range of 25-35 kWh/100 miles, which is 0.25-0.35 kWh/mile.
I think maybe the decimal place is correct but the units aren't. Isn't it 3.6 miles/kWh?
 

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Discussion Starter · #10 ·
Bubbajet, is your decimal place correct? 3.6 kWh/mile translates to about 40 cents/mile where I live (Portland, OR metro area, with electricity cost about 11 cents/kWh). The EPA ratings for EVs are usually in the range of 25-35 kWh/100 miles, which is 0.25-0.35 kWh/mile.
I think maybe the decimal place is correct but the units aren't. Isn't it 3.6 miles/kWh?
Yep, a horrendous unit error. Lordy. 'Scuse me while I go wipe this egg off my face.

And thank you for figuring that out!
 

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Finally, I do wish I had a dedicated meter for my EVSE. Maybe someday, but I've spent so much on this car already I'm having a hard time justifying that expense. Perhaps those with smart EVSEs can chime in?
I was in the exact same situation, but I successfully sent my dumb EVSE to school, see this thread Measuring kWh of a dumb EVSE using Shelly EM

I haven't driven the car since I posted that, so I still just have that one quick charge session where I charged from 68% SOC to 70% SOC. The Shelly showed 9.47 kW being supplied to the car, which totally jives with what I would expect for my 40 A Grizzl-e. I also recorded the charge session with my Car Scanner Pro OBD app, but unfortunately I didn't have it logging the initial portion of the charge session. Once I got the OBD app up and running, I saw an average charge power of 8.556 kW for the 11 minutes I recorded, so a bit over 90% of the power going into the EVSE was being converted to stored battery energy. Note that while I only recorded 11 minutes, I have always found my home level 2 charging to be very stable in the power level. While the voltage of the battery rises, the current falls leaving power constant.

Also, I have had other Shelly devices (PM1 devices) and have always found their power measurement very accurate.

So I had about 10% loss, and I'm going to guess the 2 largest components of loss were the car's inverter and the battery cooling. The radiator fan was running throughout the session and continued running for a couple of minutes after the charge session was complete. (Note that that post-session cooling is an additional loss that I'm not accounting for when I just look at the power during the charging session itself.)

I'm be doing some driving this weekend, so I try to capture some better recordings to quantify the power loss.

I've seen quite a few meters that use an RMS clamp and they're not terribly expensive. But even as easy as they look to install, I'm not confident in my ability to play with that much juice.
That's relatable. When I did my Shelly EM installation I checked that I turned off the circuit breaker about a dozen times and used my DMM about the same number of times to make sure there was no line voltage in my NEMA 6-50 box. But once I established that I wasn't going to shock myself, the Shelly installation is really easy.
 

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Discussion Starter · #12 ·
I was in the exact same situation, but I successfully sent my dumb EVSE to school, see this thread Measuring kWh of a dumb EVSE using Shelly EM

...

When I did my Shelly EM installation I checked that I turned off the circuit breaker about a dozen times and used my DMM about the same number of times to make sure there was no line voltage in my NEMA 6-50 box. But once I established that I wasn't going to shock myself, the Shelly installation is really easy.
Absolutely cool. Thank you!
 

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Ok, I got to record a home Level 2 (40A) charging session after doing some driving today and recorded it with both my OBD app and with my Shelly EM device that measures the power that goes into my Grizzl-e Classic.

The last time the car was charged was 5 days ago on July 6 using my Grizzl-e (the session I wrote about in post #11) where it charged up to SOC 70%. The day after charging it, I unplugged and just drove the car to the end of the driveway so that I could park it in the garage pointing the other direction. I didn't plug the car back in, so it sat there doing nothing in the garage for the next 4 days. (Thanks Covid work-at-home life.)

Today's driving was in hot conditions with 3 passengers and heavy AC use. At one point I started the AC several minutes before we got back to the car. Despite that I got pretty good efficiency since some the miles were in the city:

4355


76 miles of driving (and cooling) at 3.4 mi/kWh works out to 22.35 kWh expended since the last charge.

A couple of screeshots of the OBD app's view of the charging session:

4356
4357


I exported the CSV file to my computer to integrate the charging power: 8.61 kW average over 2h 49m 17s works out to 24.29 kWh of charging. What's interesting is that I left the SOC target set to 70%, so ideally it seems like the driving power, 22.35 kWh, should have matched the power needed to replenish to 70% SOC, 24.29 kWh. I'm not concerned that it doesn't match exactly, I'm just not sure why it doesn't match. Maybe the car lost some charge while it was setting idle for 4 day at 70%? If so, it seems like it would have been reflected in the efficiency knocking my 3.4 mi/kWh to a lower number. It would be cool if anyone has insight into that.

Now it's time to look at the energy supplied to my Grizzl-e. Here are a couple of screenshots of the Shelly app during the charge session and just after it ended:

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4359


The first shows an instantaneous power draw of 9.45 kW and the second shows the total energy delivered during the charge session, 26.11 kWh. Unlike last time, I didn't sit in the car and when the charging session ended and the Grizzl-e power draw dropped to 1.4 W immediately, so all of the 26.11 kWh was delivered during the 2h 45m charging session. The 24.29 kWh calculated from the OBD app data is 93.0% of the 26.11 kWh the Shelly measured. Again, it was a hot day today so that 93% seems good knowing that a good bit of energy had to go into maintaining the battery pack temperature.

So in summary, 26.11 kWh -> EVSE -> 24.29 kWh (93.0%) to return the car to 70% SOC according to OBD -> 22.35 kWh (92.0%) according to the car's report of 76 miles @ 3.4 mi/kWh after charging the car to 70% SOC 5 days ago.

Would love it if anyone can shed light on the losses. Again, I'm not concerned about the losses because they seem reasonable--just curious.
 

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Ok, I got to record a home Level 2 (40A) charging session after doing some driving today and recorded it with both my OBD app and with my Shelly EM device that measures the power that goes into my Grizzl-e Classic.

The last time the car was charged was 5 days ago on July 6 using my Grizzl-e (the session I wrote about in post #11) where it charged up to SOC 70%. The day after charging it, I unplugged and just drove the car to the end of the driveway so that I could park it in the garage pointing the other direction. I didn't plug the car back in, so it sat there doing nothing in the garage for the next 4 days. (Thanks Covid work-at-home life.)

Today's driving was in hot conditions with 3 passengers and heavy AC use. At one point I started the AC several minutes before we got back to the car. Despite that I got pretty good efficiency since some the miles were in the city:

View attachment 4355

76 miles of driving (and cooling) at 3.4 mi/kWh works out to 22.35 kWh expended since the last charge.

A couple of screeshots of the OBD app's view of the charging session:

View attachment 4356 View attachment 4357

I exported the CSV file to my computer to integrate the charging power: 8.61 kW average over 2h 49m 17s works out to 24.29 kWh of charging. What's interesting is that I left the SOC target set to 70%, so ideally it seems like the driving power, 22.35 kWh, should have matched the power needed to replenish to 70% SOC, 24.29 kWh. I'm not concerned that it doesn't match exactly, I'm just not sure why it doesn't match. Maybe the car lost some charge while it was setting idle for 4 day at 70%? If so, it seems like it would have been reflected in the efficiency knocking my 3.4 mi/kWh to a lower number. It would be cool if anyone has insight into that.

Now it's time to look at the energy supplied to my Grizzl-e. Here are a couple of screenshots of the Shelly app during the charge session and just after it ended:

View attachment 4358 View attachment 4359

The first shows an instantaneous power draw of 9.45 kW and the second shows the total energy delivered during the charge session, 26.11 kWh. Unlike last time, I didn't sit in the car and when the charging session ended and the Grizzl-e power draw dropped to 1.4 W immediately, so all of the 26.11 kWh was delivered during the 2h 45m charging session. The 24.29 kWh calculated from the OBD app data is 93.0% of the 26.11 kWh the Shelly measured. Again, it was a hot day today so that 93% seems good knowing that a good bit of energy had to go into maintaining the battery pack temperature.

So in summary, 26.11 kWh -> EVSE -> 24.29 kWh (93.0%) to return the car to 70% SOC according to OBD -> 22.35 kWh (92.0%) according to the car's report of 76 miles @ 3.4 mi/kWh after charging the car to 70% SOC 5 days ago.

Would love it if anyone can shed light on the losses. Again, I'm not concerned about the losses because they seem reasonable--just curious.
You have to understand that on-board AC-DC inverter is running at 93-95% efficiency on L2 ( depending on Voltage and how clean is electricity at your place of living).
Additional losses that you are mentioning are HV DC-Low DC 12V inverter . I would have do research to find exactly how efficient it is.
Another thing is battery conditioning.
What your EVSE is reporting is true energy delivered during the session.
There is PID that show exactly what was delivered to the battery pack after all losses from on board AC-HV DC inverter.
L1 charging are even more inefficient.
And is it the app you using Car scanner if I can ask.
So PID that show exactly what was delivered to the battery pack is your reference to calculate your ID4 efficiency.
Also you have to understand that there will be people complaining about not getting advertised Kwh ratings.
There is also losses from internal resistance....propulsion motor efficiency table ( around 3-4% depending at the rotor RPM) that will affect true energy delivered to the wheel.....and the last one most important is motor controller that convert HV DC to 3 phase AC.
It is quite difficult to explain ordinary way... it requires someone who understands... Electric motors ...EMF...back EMF and other things mentioned above.
From testing done by VW ID4 at moderate temperature and driving around 55 MPH without any hard acceleration and heavy use of cabin heater will have around 0.6-0.8 kWh internal losses from battery( don't get confused with with other efficiency losses mentioned above...this are internal resistance losses in HV DC battery)
I hope i have explained to my best as simple as I could why there is difference between EVSE and EV usage.
It will be even higher in the winter what you will see on EVSE and what actually really finished charging the battery pack....but this is another discussion for different thread.
 

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You have to understand that on-board AC-DC inverter is running at 93-95% efficiency on L2 ( depending on Voltage and how clean is electricity at your place of living).
Additional losses that you are mentioning are HV DC-Low DC 12V inverter . I would have do research to find exactly how efficient it is.
Another thing is battery conditioning.
What your EVSE is reporting is true energy delivered during the session.
There is PID that show exactly what was delivered to the battery pack after all losses from on board AC-HV DC inverter.
L1 charging are even more inefficient.
Ok, thanks. So the list of losses going from my home's line voltage to car battery charge would be
1. onboard AC/DC inverter of 93-95%
a. the quality of my line voltage would be factored in here, right? Dirty power means less inverter efficiency.
2. HV DC/12V DC inverter efficiency
3. battery conditioning (radiator fan and coolant pump?)
4. all the normal resistive losses in cables and connectors

If the inverter by itself is 93-95% efficient, looks like my measured 93% efficiency is right on target for a hot summer day.

And is it the app you using Car scanner if I can ask.
Yep, the one for IOS. Car Scanner ELM OBD2

And I appreciate your list of all the losses that can happen in converting battery energy into miles driven, but the question I still have is how many of those sources of loss get factored into the car's reported mi/kWh efficiency? To my simple way of thinking, all of those losses would be factored in. In my case, 24.29 kWh of energy got stored in the battery according to the OBD app and I drove 76 miles, so that works out to 3.13 mi/kWh instead of the 3.4 mi/kWh reported by the car. I want to emphasize I'm not upset or accusing anyone of anything--there are probably good reasons not to wrap all of the losses into the mi/kWh number if that's the case. I'm just wondering which losses are left out or maybe the stored battery energy is something less than what I calculate by integrating my OBD app data.
 

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Do you know offhand about what the rotor RPM is at 60 mph? Thanks.
I've done a couple of OBD scans while driving also and captured that information:

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Note that the x axes for the RPM and Speed are offset a bit--the data really lines up exactly.

Looking at the numbers, I'm seeing a 153.4 factor to convert mph into RPM. The RPMs at 60 mph would be about 9207 rpm. Of course, that will depend on tire pressure and everything else that determines the exact radius of the drive wheels.
 

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Do you know offhand about what the rotor RPM is at 60 mph? Thanks.
This is not very hard to see via PID. Motor propulsion unit is 10:1 so for each full rotation of half shaft it takes 10 rotation of rotor.
Now what you need to find out revolution per mile for tires you have... WhenI get next ID4 in Service I will record and post it.
But it is easy to find out.
 

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Ok, thanks. So the list of losses going from my home's line voltage to car battery charge would be
1. onboard AC/DC inverter of 93-95%
a. the quality of my line voltage would be factored in here, right? Dirty power means less inverter efficiency.
2. HV DC/12V DC inverter efficiency
3. battery conditioning (radiator fan and coolant pump?)
4. all the normal resistive losses in cables and connectors

If the inverter by itself is 93-95% efficient, looks like my measured 93% efficiency is right on target for a hot summer day.



Yep, the one for IOS. Car Scanner ELM OBD2

And I appreciate your list of all the losses that can happen in converting battery energy into miles driven, but the question I still have is how many of those sources of loss get factored into the car's reported mi/kWh efficiency? To my simple way of thinking, all of those losses would be factored in. In my case, 24.29 kWh of energy got stored in the battery according to the OBD app and I drove 76 miles, so that works out to 3.13 mi/kWh instead of the 3.4 mi/kWh reported by the car. I want to emphasize I'm not upset or accusing anyone of anything--there are probably good reasons not to wrap all of the losses into the mi/kWh number if that's the case. I'm just wondering which losses are left out or maybe the stored battery energy is something less than what I calculate by integrating my OBD app data.
Once you are off the charging plug all energy going out of the HV DC battery pack are measured and reported on the infotainment screen.....internal resistance of the battery is measured by BMS looking at various factors ...and adjusted on the fly.
Difference that you see are regeneration that is used in calculation vs by hand calculation.
 

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This is not very hard to see via PID. Motor propulsion unit is 10:1 so for each full rotation of half shaft it takes 10 rotation of rotor.
Now what you need to find out revolution per mile for tires you have... WhenI get next ID4 in Service I will record and post it.
But it is easy to find out.
I'm calculating a motor : tire revolution ratio of 12.81 : 1.

In post #17, my OBD data was showing a factor of 153.4 to convert mph to RPM.
So 60 mph = 1 mile/minute = 9207 RPM.
The center of my back axel is about 14 1/32 inches from the road surface, so 1 mile = 718.69 tire revolutions.
9207 motor revolutions per 718.29 tire revolutions works out to 12.81.

Is it possible that the RPM data from the OBD is incorrect?
 
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