Reported energy consumption [kWh/100miles] is utterly completely totally wrong - Page 2 - Jaguar I-Pace EV400 Forum
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post #11 of 14 (permalink) Old 02-17-2019, 12:21 PM
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Your second graph is interesting and indicates that the SOC (I assume this was taken from the car and not from the charger) is fairly linear during charging in the 30-65% interval range.

However, even if we assume linearity between 0-99% your calculation in the table will not be correct without accounting for the much larger 100%(full)-99% and 0%-empty slots.

If we account for these 6kWh then each percentage used in the interval 99-0% will have a size of (84.7-6)/99 = 0.795 kWh.
If we do the same calculation as in the table using these numbers we will get:
29*0.795 = 23.06kWh. If we account for roundoff errors in the displayed values for SOC the range of consumed energy will be [22.26kWh-23.85kWh].
In other words, these seemingly 29% of battery actually represents somewhere between 26.3 and 28.2% of the net battery capacity.

I agree there is still a discrepancy in the numbers, but I'm not really willing to conclude that the reported average consumption is the bad guy here.
There are at least two other alternatives.
- Reported SOC could be inaccurate
- There is less energy in the battery than the claimed 84.7kWh. We know that the colder it gets, the less energy can be harvested due to increased internal resistance.
If we assume that the reported average consumption does not include the extra heat generated due to this increased resistance (which I guess is logical) then
we can only make sensible measures at fairly warm battery temperature.
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post #12 of 14 (permalink) Old 02-17-2019, 12:40 PM Thread Starter
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The battery is a nominal 90kWh and the usable range (i.e., the 0-100% range) is supposedly 84.7 kWh. I think it's actually less but not 6 kWh less. I agree that there are confounders but they can't explain the results.

Regardless of SoC, I recommend the following to convince yourself that something weird is going on with the consumption calculation: drive hard for a few miles, watch the real time kWh/100miles figure in the Eco Data view. Then get off the freeway and watch the kWh/100miles drop precipitously even though you've only covered a tiny fraction of the total distance driven on this 'journey'. Don't need SoC to see that something is awry.
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post #13 of 14 (permalink) Old 02-17-2019, 01:07 PM
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I looked at these screens on my LEAF back in 2011. Lost interest. It is what it is.
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post #14 of 14 (permalink) Old 02-17-2019, 01:39 PM
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Quote:
Originally Posted by sciencegeek View Post
The battery is a nominal 90kWh and the usable range (i.e., the 0-100% range) is supposedly 84.7 kWh. I think it's actually less but not 6 kWh less. I agree that there are confounders but they can't explain the results.

Regardless of SoC, I recommend the following to convince yourself that something weird is going on with the consumption calculation: drive hard for a few miles, watch the real time kWh/100miles figure in the Eco Data view. Then get off the freeway and watch the kWh/100miles drop precipitously even though you've only covered a tiny fraction of the total distance driven on this 'journey'. Don't need SoC to see that something is awry.
When 0-100% is used like this a lot of people tend to misunderstand. The net capacity of 84.7% is measured from where the BMS stop any further charging (real net 100%) until the BMS will stop any further draw of current (real net 0%). These levels are not the same as the displayed SOC 0 and 100%. There is about 3kWh between a full battery and when the meter starts showing 99%. In other words the car can show 100%, but still lack 3kWh of charge compared to a full battery.

Also, we all know that the car does not come to a halt as soon as the display show 0%. There is more energy there to use.

The usable capacity and the EPA and WLTP ranges are measured between these two extremes.
In addition, there is a brick protection ofr 90-84.7 = 5.3kWh which you cannot use. This buffer is there to prevent damage to the battery.
(disclaimer : It seems to be possible to add some energy through the regen system into this brick protection buffer)

You might be correct that there are weird short term fluctations. I really haven't done much analysis over short distances. I have made a lot of observations over longer trips though, and the average cnsumption displayed has looked fairly reasonable. Also the 100%(full battery) to low number SOC looks OK and do not conflict with average consumption. It's only when I perform measurement in the mid range of SOC I get into this discrepancy.
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