Hypermiling the i-MiEV

[Aerowhatt]

I thought of a quantitative test for this best gear choices for the hypermiling debate.

Using a well known stretch of highway, I used canion to compare two back to back (as identical as possible) runs. One using D and N as needed and the other leaving the car in B the whole time. Both runs I used the same efficient (smooth changes and finessed pedals) driving style. Reseting the trip at the base of the on ramp and taking a screen shot at the stop sign at the end of the off ramp. I found the details interesting. The most important data is the Mi/kWh summary achieved for each run.

Using D and N as needed the result was 9.5 Mi/kWH

Using D and N as needed

pict_2018-06-30_09-32-08.png (120.43 KiB) Viewed 8169 times

Using B full time for the run the result was 7.9 Mi/kWh

Using B mode only

pict_2018-06-30_09-44-08.png (121.42 KiB) Viewed 8169 times

The bottom line is that D and N as needed resulted in 9.5/7.9 = 120 % the efficiency of the same drive at the same speed under the same conditions in B mode.

On the way home I thought "hey I should have done the test in every drive mode for comparison". I'm curious, so I will go back and compare full time D, E, and B again under the same conditions.

Aerowhatt

[Aerowhatt]

For completeness I went back and compared E mode and B mode on the same stretch of road. Take note that this was a different day and conditions were different than the conditions in the graphics in the previous post. In the previous post there was a pretty decent headwind. In the following results there was a slight tailwind.

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Eco mode only

thumbnail-2.png (89.92 KiB) Viewed 8168 times

B mode only

thumbnail.png (91.69 KiB) Viewed 8168 times

Aerowhatt

[DkubusEV]

'Loose efficiency?' - Better tighten that up!!

It all depends on the driver - You can 'coast' in B without shifting to N just by feathering the pedal so you're neither using power nor regenning. One pedal driving, no shifting required. The ammeter on the dash will tell you when you're in that sweet spot, but once you get used to driving this way, you can tell by the seat of your pants when you're neither using power or braking . . . . and when you need braking, just lift all the way off and you won't be swapping your foot from the go pedal to the brake

Don

The sweet spot doesn't matter because "coasting" in gear doesn't exist. When in gear the inverter is energized and supporting a rotating field in the motor which matches the rotational speed of the motor armature (which requires power to do). "Coasting" in gear is actually regening enough, to make enough power to create and support this field. It's easy to demonstrate to yourself with canion. A downslope on which you can steady state coast (in N) at 40 mph will yield an instantaneous miles/kWh in the range of 13 to 19 (in any drive gear while the amp needle is held at zero). That same stretch at 40mph in N will yield an instantaneous miles/kWh in the range of 130 to 190. It is ten times less efficient to "Coast" in a drive gear as you describe, than to actually coast in N. It's not in question, it is a demonstrable fact! Zeroing the needle in a drive gear is a very different thing than shifting into N. The second one is rightly called coasting. The first one is something else entirely.

Aerowhatt

P.S. The guy who did 97 miles recommending B as the most efficient mode for Hypermilin. He simply doesn't know any better. B mode is only most efficient for "jack rabbit driving" because it reduces friction braking in the driving style. Hypermiling is the antithesis of "jack rabbit driving" . . . so. He could do much better than he did using D and N. It's a a mathematical fact.

Absolutely what I would have thought would be the case, cheers for the confirmation. ive been driving my petrol cars like this my whole driving life and it gets me great economy. I think for my vehicle I will try to wire in some "swap over relays" so that I can just have a switch that can control a "dead man pedal" switch so that if you activate the "coast switch" then every time you lift off the accelerator pedal completely then the relays will select N right away until you re-apply the pedal....

just a theory for now as I still need to construct my aero body and install my 2010 imiev into it.

[bradleydavidgood777]

P.S. The guy who did 97 miles recommending B as the most efficient mode for Hypermilin. He simply doesn't know any better. B mode is only most efficient for "jack rabbit driving" because it reduces friction braking in the driving style. Hypermiling is the antithesis of "jack rabbit driving" . . . so. He could do much better than he did using D and N. It's a a mathematical fact.

I have been practicing hyperspacing a lot - sometimes to work and back. Went to the shore two days in a row this past weekend. Charged at the Nissan dealer half way there both times but basically proved that I could make it all the way at a reasonable pace. And one long stretch is two lanes each way so I can go slow no problem and gain extra range. Anyway, more on that later and videos to come, maybe tomorrow! The point of this post is that I completely agree with Aerowhatt and believe that it is fact. I only drive in D and N on longer trips. I would only consider B if I was in the city in stop and go traffic and low on range. Otherwise I find it much more efficient and comfortable to drive in D and N and stay way back from others and watch way ahead so that I'm hardly using regen at all, just D and N. I get super ranges this way. When I need to brake, I do it early and just touch the brake - you can feel and see the regen level. Works very well. I don't think there is anything worth debating. The facts are stated with the canion reference and also the towing of the second i-miev. Plus it just makes sense. Completely coasting is more efficient than any gears being engaged. Less parts engaged = more efficient. Simple really.

[JoeS]

Thought I'd share a neat trick I've developed, but first some background...

My wife's i-MiEV is becoming 'range challenged'. This i-MiEV (named Moto) which we bought used was probably abused as a child. With under 45K miles on the odometer, Canion shows the battery at 32Ah and with 'normal' driving its range is down to ~45 miles. This contrasts to my other i-MiEV (named Mitti) which, despite showing 37Ah on Canion, still ekes out at least 60 miles if I need it. Remember, we sold our third i-MiEV (Mitsi) a few year back. But I digress...

I have an old GPS mounted on each of my i-MiEVs for the express purpose of using its instrument panel to easily display the Distance To Go (DTG) to a programmed destination. Here are some older photos:





I use this DTG number to bounce off the i-MiEVs RR (Range Remaining) to make sure I stay out of trouble. DTG is the upper-right number in the above photo.

As long as RR>DTG, I'm ok.

Sooo, what's the story? A couple of days ago, since my i-MiEV still had the bike rack with bikes on it, I had borrowed my wife's i-MiEV for a quick trip to a gourmet food take-out that a friend recently started (in the middle of this pandemic!), but I took a circuitous route to take care of some business and didn't fully charge before leaving. Anyway, there I was down in San Jose with 8 bars and RR-32 - 'perfectly normal' you might say, as that is exactly what my other i-MiEV would read. Hey, the trip home is only 16 miles, so what's the problem?

The problem is that the outbound trip had an altitude drop of 600ft and I hypermiled all the way on a 45mph expressway and I had started with maybe 12 bars and covered at least 20 miles going there. The trip back was freeway for 13 of those 16 miles...

I could easily have stopped at a nearby EVgo DCFC for a few minutes, but, nooo, I was determined to go straight home (I was hungry), knowing full-well that the RR=32 was, in reality, really closer to the 16 miles I had left to cover (because of the aforementioned hypermiling and altitude drop), because I was now going on a freeway (where even 55mph in the right lane is iffy) and had the 600ft climb to get back home.

Remember, the RR calculation is a moving average based on how the car was driven for the preceding 15 miles (24km).

OK, ok, I'll shut up - what's the trick?

Simple: I put my home destination into the GPS and have a nice clean DTG (Distance To Go) number displayed on the screen. 16 miles exactly. Remember, the Range Remaining is displaying an artificially-inflated 32 miles.

Trick: If I could maintain a 2:1 ratio of RR:DTG for the entire trip then I'd be ok.

Sure enough, after I hopped onto the freeway the RR started dropping precipitously and the ratio soon dropped below my 2:1 comfort level... long story short, arrived home with one bar blinking... whew!

After over 150,000 miles combined of i-MiEV driving neither my wife nor I have ever seen 'turtle'.

Postscript: along the way I had a number of DCFC stations I could have gone to, so there was really no drama except for the last two miles climbing home.

Thanks for listening.

[ed5000]

Congratulations on "making it"!

This could have been a very difficult dilemma as you would need two different fuel sources. To solve this you would have to turn around and coast downhill to the nearest fast charger and plug in. Then you could hunt around for some emergency fast food. A fossil fuel gas station sandwich would also have done the trick.