Power appears to be dependent on regen mode

tomrh · Oct 16, 2013

Try the following: drive 55-60 mph on a flat road in D-mode. Keep the right foot calm, don't increase or decrease speed. Observe the power gauge, it should be somewhere in the green eco area. Now switch from D to B, observe the power gauge after a couple of seconds, remember to keep everything else unchanged. What happens?

Does anyone have an explanation of this phenomenon?

(We have a discussion going on at the Norwegian i-MiEV forum.)

Llecentaur · Oct 16, 2013

My Czero is probably always in B.

Let me guess, power gauge goes up, car accelerates ?

PV1 · Oct 16, 2013

Don't know about the faster speeds, but nothing changes around 40 mph.

tomrh · Oct 17, 2013

Llecentaur said:
My Czero is probably always in B.

Let me guess, power gauge goes up, car accelerates ?

When switching from D to B, power gauge goes down. And the higher speed the more significant jump. But speed remains constant. That's what's really puzzling me.

In other words, driving in B seems to improve range compared to D. I tested it yesterday, I actually spent 6 battery bars on my commuter distance in B where I normally would spend 7 in D.

tomrh · Oct 17, 2013

BTW - it just came to my mind that my observations may not be possible to reproduce in an US i-MiEV since the regen modes are different.

My european i-MiEV: C has less regen, D has medium regen and B has the strongest regen.

US i-MiEV: D has less, Eco has medium and B has the strongest regen? Then my C is your D, and my D doesn't exist in a US i-MiEV (it should equal to Eco w/respect to regen, but european D has no power restrictions, we have no Eco mode).

But still it would be interesting to know if there actually is a diffenence in power consumption among the various driving modes of your US/Canadian cars?

NeilBlanchard · Oct 17, 2013

Maybe the B mode has the limited power setting like the Eco mode?

siai47 · Oct 17, 2013

Two things are in play here. First, let's talk about regeneration and not pedal postion. Starting in D and then E and finally B, the amount of regen increases with each change. If you want to check it yourself, start out at a steady speed (say 100 KM) in D and release the accelerator. Watch the regen gauge then move to E and then to B. Each time you will see more regen. As far as driving modes and pedal "feel" the D and B mode use the same pedal postion and movement to create the same amount of torque from the motor---only the amount of regen changes when the pedal is released. The E mode feels different as the pedal response is "softer" then the other two modes. For example, you need to push the pedal farther to achieve the same motor torque then in the other two modes. That's why (if you hold the pedal position constant) the car slows down when going from D to E and then picks up speed again going to B. Even though you can acheive the same power output in E as in the other modes, the pedal needs to be pushed all the way to the floor before the position/torque maps match. Therefore the E mode keeps torque output more consistant when applying minor inputs and limits the excessive use of torque when not needed---that's the ECO part of the deal.

RobbW · Oct 17, 2013

Herein lies my conundrum. Up until last week or so, I have been having fun shifting through all the modes as necessary to optimize my range. I like to bump up into N when I can coast for long distances and then bump down through each mode to gradually "brake" my speed using regen as I approach a stop. This past week or so, I have started to tire of the constant shifter jockeying and decided I wanted to just pick one mode and use that exclusively. Doing so allows me to relax and enjoy the ride more. However, I cannot decide which mode I want to stick with, Eco or B. I like the controlled, efficient torque of Eco mode, but really like the strong regen of B mode. I really wish Mitsu had reversed some of the features of the Eco and B modes. I would prefer Eco at the bottom with its limited torque/power AND with the max regen from B mode. I want B mode second after D mode with the same max power output as D but slightly more regen.

Don · Oct 17, 2013

I wish 'B' was where 'D' is because I drive in 'B' 100% of the time and shifting from neutral to the next click is easier than me having to shift all the way down through 'D' and 'Eco' to get to 'B'

Actually, what I *really* wish for is a paddle on the steering wheel which would give you max regen when you pull it - That way, you could use any mode you liked and have max regen available anytime you liked - Best of both worlds

Don

Malm · Oct 17, 2013

tomrh said:
Llecentaur said:

My Czero is probably always in B.

Let me guess, power gauge goes up, car accelerates ?

Click to expand...

When switching from D to B, power gauge goes down. And the higher speed the more significant jump. But speed remains constant. That's what's really puzzling me.

In other words, driving in B seems to improve range compared to D. I tested it yesterday, I actually spent 6 battery bars on my commuter distance in B where I normally would spend 7 in D.

I have verified it myself on my i-MiEV. Driving steady, with constant speed and keeping the accelerator pedal steady, when i changed to B amperes used fall by 7, and then go up after i return to D.

tomrh · Oct 17, 2013

Malm, thank you for supporting my claim by measurements!

What siai47 says makes sense, but I experience that the power gauge jump is not followed by a speed change. My speed remains constant, only the power gauge changes. While power consumption is low and speed is high, as would be on a flat road, B seems to require less power than (european) D.

Tonight I drove 45 mph upwards a hill, and the power gauge was in the white area to keep that speed constant. I switched back and forth between D and B. And guess what, this time D displayed less power consumption than B. Both speed and pedal depth were constant during the "gear" shifts.

That makes me believe that (european) D is somehow optimized for high power driving and B is optimized for low power driving. I also experience that B and C (european Comfort mode) has the same pedal vs power characteristics except for regeneration where B has a lot and C almost nothing.

Malm · Oct 17, 2013

I confirm what tomrh says, the power gauge jump in not followed by a speed change. When we change to B, we don´t feel any kind of breaking, and the instrumentation confirm that. And the car just keep on going at the same speed.

Don · Oct 17, 2013

Interesting

I've always felt that I go farther using 'B' mode all the time, but I assumed it was because I was using the brakes so little because I was using regen for slowing all the time, but now it appears there may be even more to it

Don

siai47 · Oct 17, 2013

We might be looking at apples and oranges between the calibration of the drive system in the European vs. US spec vehicles. I my US spec vehicle, without changing pedal postion, a shift from D to E will show a current reduction (as indicated by the dash gauge) and slow the car. Going from E to B will increase current and start to pick up speed. Going from D to B (or vise versa) shows no change in current or speed. Going from E to D will also increase current and start to pick up speed. That's what I have observed in both of my I-MiEV's. For urban driving I find the E (ECO) mode works out best for me, however like other posters, I would like more regen in ECO.

tomrh · Oct 18, 2013

That might be true, siai47. Eco seems to be completely different, we have no power restrictions on the european driving modes.

But dwelling at the measurements by Malm, is it really possible to optimize an electric motor within specific current ranges? In B mode it appears that engine losses are somehow minimized while drawing small currents. But this comes at the price of bad efficiency while drawing much higher currents. The opposite with european D-mode where low currents seems to have the lower motor efficiency. This mode is obviously meant for urban and "sports" driving with higher accelerations and decelerations.

Gasoline and diesel engines are different, diesel engines are more effective at lower rpm's. But even gasoline engines may be tuned to have very different efficiency curves vs rpm. As an example, my old Mitsubishi Spacewagon 2.4 GDI has a much higher torque and efficiency at lower rpm's than normal gasoline engines. Maybe we observe the same with i-MiEV - the driving modes are simply a selection of different tunings of an electrical motor?

Malm · Oct 18, 2013

tomrh said:
That might be true, siai47. Eco seems to be completely different, we have no power restrictions on the european driving modes.

But dwelling at the measurements by Malm, is it really possible to optimize an electric motor within specific current ranges? In B mode it appears that engine losses are somehow minimized while drawing small currents. But this comes at the price of bad efficiency while drawing much higher currents. The opposite with european D-mode where low currents seems to have the lower motor efficiency. This mode is obviously meant for urban and "sports" driving with higher accelerations and decelerations.

Gasoline and diesel engines are different, diesel engines are more effective at lower rpm's. But even gasoline engines may be tuned to have very different efficiency curves vs rpm. As an example, my old Mitsubishi Spacewagon 2.4 GDI has a much higher torque and efficiency at lower rpm's than normal gasoline engines. Maybe we observe the same with i-MiEV - the driving modes are simply a selection of different tunings of an electrical motor?

Tomrh, i´m following your findings and i'm amazed. Just keep going, i think you are going in the right path. Let me say you three sings: congratulations, congratulations and congratulations for your findings. I will support you with my data, if they confirm what you are reporting. Maybe tomorrow i can obtain some unambiguous graphs.

tomrh · Oct 18, 2013

Thanks, Malm. I must add that it was another Norwegian guy with nick "uppis" who initially discovered this. I followed his instructions and was pretty amazed. The i-MiEV continues to surprise me, there is always more to its inner workings than we think we already know. I do not know electric motors very well, but googling "electric motor tuning" brings forward many hits where racing enthusiasts give away tuning tips for maximizing power etc. And some say they use software for tuning. So some sort of built-in tuning profiles should be possible.

As I said I'm not at all into the inner workings of electrical motors, but I read somewhere that the magnetic field strength of the permanent magnet has a square impact. And then I thought of something. Could it be that some secondary current is used for increasing the strength of some magnetic field, which in turn would provide higher efficiency? The idea is that the european D mode would enable this current while B disables it. And at low power consumption this secondary current becomes significant, meaning D uses more power than B. Just a thought. Hopefully someone with a more profound knowledge of electric motors will comment on this thread.

NeilBlanchard · Oct 19, 2013

Quick side note: the Smart Electric Drive has an option ($190) for paddles behind the steering wheel, that let you toggle between no regen, normal regen, and maximum regen. That's a no-brainer. Oh, and the lease is $2K down and $139/month for the base Smart ED. Heated seats are the other smart option...

Malm · Oct 20, 2013

"What siai47 says makes sense, but I experience that the power gauge jump is not followed by a speed change. My speed remains constant, only the power gauge changes. While power consumption is low and speed is high, as would be on a flat road, B seems to require less power than (european) D." tomrh, Oct 17.

"I confirm what tomrh says, the power gauge jump in not followed by a speed change. When we change to B, we don´t feel any kind of breaking, and the instrumentation confirm that. And the car just keep on going at the same speed." Malm, Oct 17.

Now in video:

http://www.youtube.com/watch?v=j-sKHw445XA

ZsoZso · Mar 13, 2014

Malm said:

Do I interpret this graph correctly if I conclude that the max regen is only about 4.5kW (328V with -120A)?
That sounds very little compared to the Tesla Model S which has 60kW max regen.

Power appears to be dependent on regen mode

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