Energy consumption - Jaguar I-Pace EV400 Forum
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post #1 of 17 (permalink) Old 02-14-2019, 01:16 PM Thread Starter
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Energy consumption

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!
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post #2 of 17 (permalink) Old 02-14-2019, 03:10 PM
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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%).

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post #3 of 17 (permalink) Old 02-14-2019, 03:31 PM Thread Starter
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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.

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post #4 of 17 (permalink) Old 02-14-2019, 04:20 PM Thread Starter
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Just trying to determine if I should trust the kWh/100mi readout or the energy meter or neither.

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post #5 of 17 (permalink) Old 02-14-2019, 05:02 PM
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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.

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post #6 of 17 (permalink) Old 02-14-2019, 10:33 PM
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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.
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post #7 of 17 (permalink) Old 02-15-2019, 10:32 AM Thread Starter
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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

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 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
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post #8 of 17 (permalink) Old 02-15-2019, 11:06 AM
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Quote:
Originally Posted by ryzvy View Post
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

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 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
QUICK go to Chip Repair shop if it hasn't spidered yet. DO NOT TURN ON DEFROSTER until you get the chip repair done.
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post #9 of 17 (permalink) Old 02-15-2019, 11:15 AM Thread Starter
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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?

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post #10 of 17 (permalink) Old 02-15-2019, 02:25 PM
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Originally Posted by ryzvy View Post
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.

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