Reported energy consumption [kWh/100miles] is utterly completely totally wrong - Page 3 - Jaguar I-Pace EV400 Forum
 5Likes
Reply
 
LinkBack Thread Tools
post #21 of 57 (permalink) Old 08-24-2019, 05:28 PM
Senior Member
 
2761's Avatar
 
Join Date: May 2019
Posts: 392
Quote:
Originally Posted by juice View Post
Another possibility is that the JLR numbers are being misinterpreted. Maybe JLR's consumption numbers are computed entirely based on energy used to move the car forward, so if you're using Max AC with seat coolers on full blast and sitting in traffic a lot, a significant portion of your battery energy may not be factored into the JLR numbers. I'm speculating without any facts or evidence.
The car certainly factors in energy consumed for AC. I watch the trip bank kWh/100 miles rapidly climb while sitting at a traffic light with AC on and notice the increase when using AC on the same route where I haven't previously used it. I don't have cooled seats so I can't comment there.

Last night I charged to 100% with WattCat reporting 82.55 available kWh. This morning I reset Trip A and will track miles travelled until next charge, Trip A kWh/100 miles and WattCat reported kWh still available. Math should be simple to determine any discrepancy between the car and WattCat. I'll continue this process for a few weeks and should have significant statistical data for analysis.
2761 is offline  
post #22 of 57 (permalink) Old 08-24-2019, 05:31 PM Thread Starter
Super Moderator
 
sciencegeek's Avatar
 
Join Date: Jun 2018
Location: Palo Alto
Posts: 1,202
Quote:
Originally Posted by eJeff View Post
For those of you who prefer the kWh/100mi metric, for my numbers above they are:

ChargePoint data: 49.26kWh/100mi
InControl Data: 40.0kWh/100mi
Can you do the following experiment: Note starting SoC (percent is fine if you don't have WattCat); Charge; Note ending SoC and kWh supplied by your charger. And report the result, preferably doing it a couple or three times? Purpose is to estimate the loss during the charging process and see how many kW actually get into the battery.

Regardless, your discrepancy is less than mine, probably because you're driving many more freeway miles and my trips are lots of accel/decel and varying speeds. JLR's estimates are particularly bad when there's a lot of variation within a drive, like mine, and not so bad when the speed doesn't vary much over longer distances, like yours.
sciencegeek is online now  
post #23 of 57 (permalink) Old 08-24-2019, 05:55 PM
Member
 
squishball's Avatar
 
Join Date: Jan 2019
Location: San Francisco, CA
Posts: 74
I did a similar analysis comparing Journey's miles/kWh to my calculations using the I-Pace's onboard SOC reading. I only did it for only one charge cycle. For 6 trips (power on-off cycle) totaling 112 miles in distance, with trips ranging from 61 miles to less than 3 miles, Journey's weighted average energy consumption (weighted by miles traveled per trip) was 2.88 m/kWh. My calculation, based on the I-Pace's SOC % reading and assuming a battery capacity of 84.7 kWh, was 2.49 m/kWh. So, Journey overstates efficiency by about 15%.


If you prefer kwh/100mi, Journey: 2.88 m/kWh = 34.68 kWh/100 m and My calculations: 2.49 m/kWh = 40.08 kWh/100 m.


Unfortunately, I can't use sciencegeek's suggestion of comparing the results to the amount of kWh supplied from my ChargePoint EVSE, because I rarely charge to 100%. So, I can't determine how much charge was consumed per charge cycle, only how much was supplied.

I-Pace FE, Corris Gray, 20" rims
squishball is offline  
Sponsored Links
Advertisement
 
post #24 of 57 (permalink) Old 08-24-2019, 06:24 PM
Senior Member
 
2761's Avatar
 
Join Date: May 2019
Posts: 392
ICE drivers probably think we're crazy to track these issues. I never cared what my vehicle displayed range was because I understood it was wrong but there was no impact due to the ease of filling up. I knew that I could get around 350 miles on the highway and 300 in the city.

Likewise I knew the car-displayed MPG wasn't terribly accurate but easy to determine when I filled up.

EVs are different because consumption and efficiency are critical to determining range. Predicted range is vital for planning charging stops. When the EV is providing inaccurate figures, especially when underestimating consumption, drivers can end up stranded.

So my key question is: if the car can accurately determine available kWh, as shown by WattCat, why can't it determine consumption?
2761 is offline  
post #25 of 57 (permalink) Old 08-24-2019, 06:31 PM
Senior Member
 
Join Date: Sep 2018
Location: So Calif
Posts: 417
How is charging efficiency accounted for?

Car counts energy from the battery. Wall unit counts energy from the wall. Between the pumps, battery conditioning, conversion losses, charging the 12v battery, telemetrics, general heat losses.... the two are just not going to match up.
Time2Roll is offline  
post #26 of 57 (permalink) Old 08-25-2019, 02:11 AM
Senior Member
 
2761's Avatar
 
Join Date: May 2019
Posts: 392
Quote:
Originally Posted by Time2Roll View Post
How is charging efficiency accounted for?

Car counts energy from the battery. Wall unit counts energy from the wall. Between the pumps, battery conditioning, conversion losses, charging the 12v battery, telemetrics, general heat losses.... the two are just not going to match up.
Interesting to note that tonight WattCat showed 6.6 kWh added while the Chargepoint app reported 6.49 kWh added. It's a close number and appears to show no loss at the box or cable. I didn't expect to see more going into the battery than was reported by the app.
2761 is offline  
post #27 of 57 (permalink) Old 08-25-2019, 03:54 AM
Member
 
Join Date: Dec 2018
Location: Monte Sereno, CA
Posts: 40
Quote:
Originally Posted by Time2Roll View Post
How is charging efficiency accounted for?

Car counts energy from the battery. Wall unit counts energy from the wall. Between the pumps, battery conditioning, conversion losses, charging the 12v battery, telemetrics, general heat losses.... the two are just not going to match up.
At the end of the day, the only efficiency measurement that matters is how much distance you get from the energy you put into the vehicle. This is the same as measuring how much distance you can go from pumping a gallon of gasoline from the pump. Any loss of efficiency between the charger and the car is part of the deal.

That said, I doubt there is 23% loss of efficiency between the charger and the battery, which is what would be required to make the numbers from the InControl app match the numbers from ChargePoint. It would be very poor engineering if that were the case. @sciencegeek , I will do my best to measure it. Interestingly, ignoring the efficiency reported by JLR, my measurement of 49kWh/100mi is pretty close to your measurement of 46kWh/100mi. The 3kWh (6%) difference could be the charger efficiency issue.
sciencegeek likes this.
eJeff is online now  
post #28 of 57 (permalink) Old 08-25-2019, 11:57 AM Thread Starter
Super Moderator
 
sciencegeek's Avatar
 
Join Date: Jun 2018
Location: Palo Alto
Posts: 1,202
Quote:
Originally Posted by CurtSprings View Post
So my key question is: if the car can accurately determine available kWh, as shown by WattCat, why can't it determine consumption?
Exactly
sciencegeek is online now  
post #29 of 57 (permalink) Old 08-25-2019, 02:45 PM
Member
 
Join Date: May 2019
Location: Montreal, Canada
Posts: 94
Quote:
Originally Posted by CurtSprings View Post
ICE drivers probably think we're crazy to track these issues. I never cared what my vehicle displayed range was because I understood it was wrong but there was no impact due to the ease of filling up. I knew that I could get around 350 miles on the highway and 300 in the city.

Likewise I knew the car-displayed MPG wasn't terribly accurate but easy to determine when I filled up.

EVs are different because consumption and efficiency are critical to determining range. Predicted range is vital for planning charging stops. When the EV is providing inaccurate figures, especially when underestimating consumption, drivers can end up stranded.

So my key question is: if the car can accurately determine available kWh, as shown by WattCat, why can't it determine consumption?
You might be generalizing a bit here. In my limited experience, unless I am taking trip where I need to plan my stops, my interest in consumption and range estimates are purely academic as a curious engineer. When all I am doing is driving to/from work and usual errands, I pay no attention to the consumption as I know I can go a week or more between charges, and since I can plug in any night I want at home, the range is not factor. When I feel like taking 30 seconds to actually plug in the cable, I just do it and don't need a spreadsheet or protractor to decide that. I usually do so on Friday so I have a full charge in case I want to go for a trip to the country.

Of course the engineer in me wants to have that spreadsheet going since i am curious, but it does not cause any anxiety.
rcomeau is offline  
post #30 of 57 (permalink) Old 08-25-2019, 03:18 PM
Senior Member
 
McRat's Avatar
 
Join Date: May 2018
Location: Norco, California, USA
Posts: 1,352
I'm now of the belief that something is wrong with the latest flash when it comes to reporting.
I'm stuck at 201 miles again, but the kW / 100 miles is not lining up with actual driving conditions anymore.
Hoping for a new flash. Wish I hadn't done the OTA flash.

Jaguar i-Pace FE Photon Red 20" wheels, "Leaper"
Two Chevrolet Volts in service
24.2 kW x 480v 3ph solar array self-installed.
McRat is offline  
Reply

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Forum Replies Last Post
Energy consumption ryzvy 2018+ I-Pace EV Range, MPGE And Economy 16 02-16-2019 01:25 PM

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome