Can anyone explain this - Jaguar I-Pace EV400 Forum
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post #1 of 10 (permalink) Old 02-05-2020, 07:43 PM Thread Starter
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Can anyone explain this

So can anyone explain this math to me

I drove 11.2 miles today.

Jag App said it used 2.34 mile/kWh

11.2 / 2.34 = 4.78 kWh used to drive 11.2 miles

JAG app said I regenerated 4.6 kWh. I drove on free way and showed down from 70 to 40 mph many times in order to regenerate that much power. It was early in the morning so it was safe. I know I probably would have used more energy to reaccelerate back to 70 mph but I am going by what the app said during my trip.

How is it possible that I used average of 4.78 kWh to drive here and I regenerated 4.6 kWh during the trip.

If I did the math correct, I should have only used .18 KWH to drive the 11.2 miles.

Odometer started at 188 and when I arrived to work it was down to 173 miles.

HOW IS THIS POSSIBLE if the car regenerated 4.6 kWh X 2.3 miles per kWh = 10.58 miles driven using what was regenerated.

Can someone help me make sense of this.
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post #2 of 10 (permalink) Old 02-05-2020, 07:46 PM Thread Starter
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Is the regeneration feature just a scam? Has anyone actually ever seen the battery mileage roll back wards or stay the same?

Maybe they are scamming us and making us believe we generate power to make use feel better about buying EV’s.
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post #3 of 10 (permalink) Old 02-05-2020, 07:50 PM
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While I never paid attention to kWh Regen values:

You could regen 4.6 kWh in an 11.2 mile trip and consume 4.78 kWh of battery. If the power output to the motors was 9.38 kWh, and it recovered 4.6 of that, then the consumption would be 4.78.

But it sounds more like the regen number is calculated wrong unless there is a huge hill in that 11.2 miles.

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post #4 of 10 (permalink) Old 02-05-2020, 07:54 PM
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Regen is not as important as you might think. It has no effect on steady state driving. Aero losses are much greater once you pass 60 mph.
It works best in stop and go traffic in heavy cars.
The best economy you'll see is when there is very little regen. Because it can only recover at best 80% of the kinetic energy.
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post #5 of 10 (permalink) Old 02-05-2020, 07:54 PM
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Some of the Regen might have gone back into the battery and was not used immediately.

The bigger question is the odometer. Did the GoM decrease or odometer? I know it's a crazy question but I want to be sure. I've never heard of an odometer rolling backwards.
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post #6 of 10 (permalink) Old 02-05-2020, 08:30 PM
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In the old days of cable driven rolling number odometers, they could roll backwards. In the modern days of using Hall effect sensors to detect axle/differential/other related parts rotation odometers will always go forwards. The op must have meant the guess meter went from 188 to 173.

Yes, I've seen the guess go up a small amount during regen and driving downhill with regen, or using a little energy, can cause the guessing to go up since it is factoring in the decreased energy usage to traverse the distance.

The guessing has a number of factors taken into account. I think one of them is how much it wants to mess with the driver's mind at that moment.
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post #7 of 10 (permalink) Old 02-05-2020, 10:05 PM
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Quote:
Originally Posted by cjpardo View Post
So can anyone explain this math to me

I drove 11.2 miles today.

Jag App said it used 2.34 mile/kWh

11.2 / 2.34 = 4.78 kWh used to drive 11.2 miles

JAG app said I regenerated 4.6 kWh.

Can someone help me make sense of this.
I believe the app may be reporting the net kWh used. Thus the actual energy used on your trip would be the "4.47 kWh" plus the regenerated 4.6kWh. This would be more in line with constant acceleration/regen braking and running at 70mph.
4.6kWh of regen does seem high. Is your journey predominantly downhill. I commute 18miles to work down a valley and home back up the valley. I see significantly more regen going into work than returning.
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post #8 of 10 (permalink) Old 02-05-2020, 10:30 PM Thread Starter
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Maybe this will help.

I know the regeneration was high but I purposely drove like an idiot to regen as much as I could. When I normally drive the route, it will regen about 1.5 to 2 kWh.

This morning I purposely was letting go of the accelerator to max regen. I would go to 70 and then let go the accelerator and allow it to regen down to 40. I repeated this process many times in order to maximize regeneration.

The problem I have is what the app is telling me. If I did the math correct, I almost used as much energy driving to equal the amount regenerated.

If that’s the case, why did the battery eat up so many miles on the range. It almost makes sense that it used up that amount of mileage on the battery because accelerating to 70 many times would use a lot of energy. So that part makes sense. What does not makes sense is what is reported in my car as regenerated power of 4.6 kWh.

When I meant odometer going backwards I meant to say if anyone has ever noticed regen adding to the battery range?
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post #9 of 10 (permalink) Old 02-05-2020, 11:22 PM
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[The miles/kWh figure the car reports can be off by a bit under the driving conditions you forced upon the vehicle; that said, let me try to explain the same thing that McRat said]

The car reports net consumption in miles/kWh. You drove 11.2 miles like an idiot and used 4.78kWh per your calculation. Given how you drove, that's a reasonable consumption number.

The car also reports the regen value. Because you repeatedly forced it into regen, the total regen number is high.

The *net* consumption reported by the car folds that regen number in. The net consumption is mostly correct. The regen number is for your entertainment. How is it interesting? It's interesting because if you had driven an ICE car that regen value would have been lost to friction brakes, and not recovered. So your overall consumption was still reasonable, even though you drove like an idiot.
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post #10 of 10 (permalink) Old Yesterday, 07:33 AM Thread Starter
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Thanks for the explanation
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