Question

[bkittner]

I've had my MME for just over 1 year. I've been tracking trips as well as charging stats. I recently did an end-of-year (2022) summary and notice a difference between what the app reports as kW used in driving vs. kWh shown from charging. 95% of my charging is done at 120v. The sum of the energy used from trips reported by the app is 599 kWh from 2126 miles driven. The app occasionally fails to report trips (wish I knew why), so I estimated approx. 100 miles in missing trip data which brings the mileage to 700 miles. Using the overall average of 2.8 miles per kWh, missing trip data would add ~35 kWhs, bringing the total kWhs reported used by driving to 635.

The charge log reports showed 1042 kWh delivered by charging over this same period. Any suggestions on why charging data shows ~40% more kWhs from charging vs kWhs used for driving? Statistically my mileage (usage) is low, I rarely use heat or A/C... and I use the steering wheel heat sparingly, so I don’t believe that would account for the difference (and even so, isn't ALL energy used included in the 'driving energy used' stats?). I believe I understand issues with charging and range in cold weather, but it’s hard to believe ‘battery heating’ during charging accounts for the difference, as there is only minor variability between summer and winter charging, averaging 54 mins and between 2.6 and 3.1 miles per kWh delivered without a significant difference between winter and summer months.

Note: In the chart below, except for the first few charges in Dec'21 and Jan'22 when I first got it and where several of the charges were too short - resulting in inaccurate stats – the rest are overnight charges with sufficient length to be statistically valid.

What am I missing?

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[bkittner]

Oops, apologies for the double chart

 

[RickMachE]

1) If you send 10kW from the wall to the car, you lose some due to resistance along the way. With 120v charging, it's about 15%. But you don't seem to have that data. If you use an intelligent charger, you can see exactly how much energy is sent from the wall to the car.

2) The car uses energy while driving from the battery and regeneration. You haven't accounted for regeneration.

3) The EV driving data, as well as Trips data, is often inaccurate. For example, on a recent trip my Trip 1 and Trip 2 miles per kilowatt hour reset, and I lost all history. EV driving data often fails to reset the miles, showing absurd efficiencies.

If you're into data, #3 is going to have you in fits.

4) Miles add from charging is near useless. It estimates miles added, when in reality what you want is kWh added, because how many miles you get per kWh is dependent on you and weather.

5) Rounding / truncating.

 

[bkittner]

1) If you send 10kW from the wall to the car, you lose some due to resistance along the way. With 120v charging, it's about 15%. But you don't seem to have that data. If you use an intelligent charger, you can see exactly how much energy is sent from the wall to the car.

2) The car uses energy while driving from the battery and regeneration. You haven't accounted for regeneration.

3) The EV driving data, as well as Trips data, is often inaccurate. For example, on a recent trip my Trip 1 and Trip 2 miles per kilowatt hour reset, and I lost all history. EV driving data often fails to reset the miles, showing absurd efficiencies.

If you're into data, #3 is going to have you in fits.

Thanks, RIckMachE!

You're correct, I didn't account for regen and delivery efficiency, but wouldn't regen require LESS charge from a/c vs. more?

Also, to your #3, I was really frustrated by this. I read somewhere (and have since successfully implemented) that if you press start WITHOUT the brake first (screen shows "Full Accessory Power Available), and THEN press on the brake and press start again, it will reset the previous trip data.

Thank you for your thoughts!

 

[RickMachE]

I was very frustrated when my Trip 2 efficiency was reset. I never reset Trip 2 from day of purchase, and now that is totally gone. I only noticed it because it went from 3.0 to 2.8, and that wasn't possible based on one trip. Then I noticed that the current trip was 2.8 at the time, and figured it out. Really annoying.

 

[mateo]

Yes, counting regen would make your problem worse from how I am understanding the question...

I would chalk it up to basically that your data isn't accurate. But I guess you already knew that. ?

The only numbers I would trust is a) something that an external meter tells you in terms of "consumed" power and b) what the odometer reads. Because that's what really matters. How much power was consumed to ultimately move the car.

 

[AKgrampy]

@RickMachE probably has better info than me but my recollection is that charging at 120V is right at 70% efficient. This is from losses as well as energy consumed on board during charging. There was a fairly long thread discussing this (once again if I am remembering correctly) and the person who was using 120V exclusively stated they were using so little electricity it was cheaper to pay the losses than install a 240V plug and switch to 240V.

 

[bkittner]

@RickMachE probably has better info than me but my recollection is that charging at 120V is right at 70% efficient. This is from losses as well as energy consumed on board during charging. There was a fairly long thread discussing this (once again if I am remembering correctly) and the person who was using 120V exclusively stated they were using so little electricity it was cheaper to pay the losses than install a 240V plug and switch to 240V.

Thanks, @AKgrampy, for your reply. But my question still remains. Even if efficiency is only 70%, if the app reports that X# of miles were added, wouldn't one think that that the number was net of what was delivered to the vehicle vs. what came from the supply? Even if efficiency loss was, say 90%, it reported <x number of miles> added... so my question remains as to why the app claims more miles are 'delivered' than the same app shows are consumed by driving.

Curious to be sure.

 

[Mr. Toejam]

I hope you have a heavy duty 120outlet. Standard house hold outlets really are not designed for a constant max draw with that kind of duty cycle. Even most 14-50 outlets are not really rated for EV duty cycles. There are multiple videos out there detailing this. As soon as the rains stop, I am checking my 14-50 and my EVSE to make sure none of the lugs have loosened up.

 

[AKgrampy]

Thanks, @AKgrampy, for your reply. But my question still remains. Even if efficiency is only 70%, if the app reports that X# of miles were added, wouldn't one think that that the number was net of what was delivered to the vehicle vs. what came from the supply? Even if efficiency loss was, say 90%, it reported <x number of miles> added... so my question remains as to why the app claims more miles are 'delivered' than the same app shows are consumed by driving.

Curious to be sure.

I am not sure the Ford Pass ap is the best place to look at this info as I believe the info may be estimated and not actually measured but I am not 100% sure on that. I know I am getting between 1.8 to 2 mi/kWh right now so for 27 kWh I’d driving I get around 54 miles but FP states 66 miles of charging. The only thing I really monitor is my mi/kWh. I just kind of keep an eye on it and have a feel for where it should be - at least for Alaska seasons.

 

[bkittner]

I am not sure the Ford Pass ap is the best place to look at this info as I believe the info may be estimated and not actually measured but I am not 100% sure on that. I know I am getting between 1.8 to 2 mi/kWh right now so for 27 kWh I’d driving I get around 54 miles but FP states 66 miles of charging. The only thing I really monitor is my mi/kWh. I just kind of keep an eye on it and have a feel for where it should be - at least for Alaska seasons.

OK, I monitor that too... so back to the original point: which do you think is more accurate, Mi per kWh the app reports from charging or Mi per kWh the app reports from driving?

 

[SuperRob]

There are so many ways this calculation can go wrong, I've found it pointless to even bother tracking this. In the month and a half I've had the car, the trip meter has been wrong probably 20-25% of the time. We garage our car, and since it uses the GPS to help determine distance, all it takes is not getting a proper GPS lock at the beginning of a trip to screw up your data for that trip.

Now I'm a data guy ... it's part of my job. But I believe in only collecting the data that you can take action on. As interesting as some of this data is, I don't think there is anything I would really change about my driving that this data would inform. (Charging losses are interesting, but the same way trivia is.) And the one thing that WOULD, trip data and efficiency, isn't accurate enough to rely on.

 

[AKgrampy]

OK, I monitor that too... so back to the original point: which do you think is more accurate, Mi per kWh the app reports from charging or Mi per kWh the app reports from driving?

Neither! I would only go by the info contained on the car’s screen and then only for Trip1 and Trip 2. For instance my ap shows trips up to 16 mi/kWh! I wish! (We are talking about Ford Pass - right?) The issue is I am auto starting to warm up the car and the mileage does not clear on MyTrip; therefore, I get 50 ish mile drive reported to FP ap using 3kWh when I really only took a short 6 mile run to the store.

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