[ryzvy]

I am very confused by how the car calculates the consumption numbers for a trip. For example I took a 36 mile trip this morning and the SoC charge went from 66% to 44%. At the end of the trip the gauge showed an energy consumption of 42.6kWh/100mi for the trip. Based on this, by my calculation I used up 15.336 kWh of energy ((42.6/100)*36=15.336). But if this is 22% of the battery (66-44=22) does that mean that the usable battery capacity is only 69.71 kWh (15.336/0.22=69.71)?? On the flip side if I assume the usable battery capacity is approximately 82 kWh, as a lot of people have calculated based on their usage, then I consumed 18.04 kWh (82*0.22=18.04) for the 36 mile trip and my consumption rate should be 50.11kWh/100 mi ((18.04/36)*100=50.11) and not 42.6kWh/100mi that the car is displaying. What am I missing? Is the car in some way using the regenerated energy in how it is calculating the consumption numbers (I tried to account for the 1.7 kWh regen but still couldn't make the numbers work). Any insight would be much appreciated as it's been driving me crazy. I have attached my calculations for a couple of trips I took. Thanks in advance for either fixing my assumptions or calculations! @sciencegeek help! :grin2:

 

[McRat]

No % meter on an EV or gas cars is completely linear. It's the nature of the beast. it's never a perfect curve. You should see engine tables in an emissions car. They need to correct the cells to optimize them to the true values to get the lowest possible emissions. So they have data scatter down all the rows.
On an EV, it is normally calculated based on battery voltage and temperature. Your battery holds more power when it's warm than cold.
Think about it:
EV range on a dry very cold day is bad. Some is tire flex, a tiny bit is air density, but the biggest part is battery capacity.

JLR says the battery actually holds 84.7 kWh, but that number would be a warm battery, from 100% down to -2% (JLR docs say the scan tool reads 2% when the dash reads 0%).

 

[ryzvy]

Thanks for your response, McRat. I understand the drop in range on a cold day, but I am not talking about the efficiency, which actually doesn't appear to be that bad but just trying to semi-accurately determine how much battery charge I have available. A more than 10 kWh difference in available capacity for a 82 kWh battery on a 50 degree day sounds a bit excessive.

 

[ryzvy]

Just trying to determine if I should trust the kWh/100mi readout or the energy meter or neither.

 

[McRat]

I know the mobile app gets it's charging rate wrong unless you set it to %/hr.
The % has been a fairly good guide for me, but I've never really mapped it accurately.

 

[sciencegeek]

I don't have anything to add here. I share your surprise ... I hadn't done that calculation myself. It seems too far off but then again as McRat says estimating SoC is not trivial. I'll pay attention tomorrow ... will put 2x70miles on it, should be a good cross reference.

 

[ryzvy]

Thanks for all the input, gents. I added a couple more data points, but all they show is that the estimation of usable battery capacity based on the displayed consumption numbers and the estimation of actual consumption number based on displayed battery SoC is inconsistent. I am going to accept it as just another "feature" of the car, will stop worrying about it and just enjoy the ride :wink2:

On a more sad note the car is barely a month old and I already received a windshield chip! I bet it's going to cost an arm and a leg to replace it :crying: I drove my previous car for ten years on the same route and never received a chip or crack, and one month in with the I-Pace this happens :frown2:

 

[McRat]

Thanks for all the input, gents. I added a couple more data points, but all they show is that the estimation of usable battery capacity based on the displayed consumption numbers and the estimation of actual consumption number based on displayed battery SoC is inconsistent. I am going to accept it as just another "feature" of the car, will stop worrying about it and just enjoy the ride :wink2:

On a more sad note the car is barely a month old and I already received a windshield chip! I bet it's going to cost an arm and a leg to replace it :crying: I drove my previous car for ten years on the same route and never received a chip or crack, and one month in with the I-Pace this happens :frown2:

QUICK go to Chip Repair shop if it hasn't spidered yet. DO NOT TURN ON DEFROSTER until you get the chip repair done.

 

[ryzvy]

Thanks @McRat! I just called one and they will have someone here within a couple of hours. I am not moving the car until they do their thing! Fingers crossed it is still repairable. I wonder if it will mess up the windshield heater wires? :|

 

[McRat]

Thanks @McRat! I just called one and they will have someone here within a couple of hours. I am not moving the car until they do their thing! Fingers crossed it is still repairable. I wonder if it will mess up the windshield heater wires? :|

I thought the chip repair was snake oil until we used it to save a $1100 windshield and it worked.

Not sure what the heater wire will do. I doubt there is that much experience. Metal wire is somewhat malleable so I'd guess it would survive, but ... worth a try.

 

[ryzvy]

No dice. Apparently they can't (don't/won't?) repair chips that are in the black painted section of the windshield like it is for me. Will have to call Jaguar for a price quote. Oh well, it was worth a try. Thanks again for the suggestion, McRat.

 

[sgtpeper]

I always recommend getting full glass coverage. I have a zero dollar deductible on glass and it has saved me a ton of money here in Denver. It adds a few bucks a month but last year alone I replaced the windshield on my X5 3 times! Each time it was 100% covered.

 

[alphanstein]

In California, a lot of insurance companies pay for the rock chip repair, no deductible as it saves them more than the cost of replacing the windshield. So you might want to check your insurance to get reimbursed.

 

[CyberSlug]

I haven’t found a company in CA yet that offers no-deductible glass coverage. I had that when I lived in AZ and we ended up using it about every other year because there are rocks all over the place.

Soon after moving to CA I had to replace the windshield on my A6 twice in 8 days. Because of all the systems that have to be calibrated that was not a pleasant experience.

 

[alphanstein]

Not no-deductible windshield replacement, it is no-deductible rock chip repair. This is different and why you want to get a rock chip repaired asap to eliminate having to pay a deductible and replace the windshield.

I have done a couple of rock chip repairs myself though thru the years, the kit is like $10 on Amazon and takes about 25-30 minutes on a nice dry day. Both times it just leaves a small looking pin prick in the glass and saves the hassle of trying to get someone to fix it and talk to the insurance company.

 

[CyberSlug]

Yep, I currently have the no-deductible chip coverage, and have used that a few times as well. I was referring to sgtpeper’s comment about the no-deductible glass coverage he has in CO.

 

[sciencegeek]

Alrighty folks this is just a friendly reminder that the title of the thread is "Energy consumption" and not "Chip coverage"

Yesterday I drove back and forth from Stanford to Walnut Creek, almost identical trips. See screenshot.

Bottom line: I also see a mismatch between %age of battery used and the consumption reported for the 'journey' [kWh/100 miles], resulting in considerably lower estimates of usable battery capacity: For both legs of the trip the implied battery capacity was ca. 74 kWh.

If I assume 84 kWh capacity and take the SoC difference at face value, I get ca. 50 kWh/100miles. That's a lot worse than the reported 36 kWh/100miles.

The end of the first 'journey' (which is the same as the beginning of the second 'journey') is at 50% SoC; the percentage used was 29 or 30. The kWh/100 miles figures are also very close. In other words, none of the estimates seem to depend on higher (first journey) vs. lower (second journey) SoC, and do not imply that the SoC estimate is off.

This is puzzling. My best guess is that the SoC estimate is pretty good and that the kWh/100 miles is off and gives us an optimistic estimate. Evidence in favor of this idea is this: Both trips involved about 80% of the miles driven at between 65 and 80 mph. I can't believe that the average consumption was 36 kWh/100miles. 36 kWh/100miles is almost exactly my long-term average, which is dominated by commute miles. The calculated ca. 50 kWh/100miles is much more realistic for that trip yesterday.

I believe that JLR's calculation of the average rate of consumption makes a rookie mistake: averaging the rate as a function of time, instead of miles driven. Additional evidence for that hypothesis is the fact that the real time estimates of consumption [kWh/100miles] rapidly decrease after driving many miles at high speed and then driving a few miles at lower speeds. I will put that to an actual test some time this weekend.