Hypermiling the i-MiEV

[Don]

I suspect most of us use these cars more in urban traffic than in places where we would want or need to use higher speed hypermiling skills. You can still get RR's of 80 or 85 miles in typical stop and go traffic if you accelerate very gently keeping the amps needle well below the mid mark *and* decelerate very gently only using the brakes after you're down to less than 10 to 15 mph. This does mean following an extra couple car lengths farther back than *most* drivers do, so you're not constantly making quick reactions to the changes in speed of the traffic in front of you

It still amazes me how many people drive with their brakelights flashing on and off several times per mile - Try not to be 'that guy'

After 'learning' to drive our EV's this way, I do pretty much the same in the gas powered cars too and the difference in MPG this makes is quite remarkable. I just keep thinking that 'Friction Braking Is Wasting Energy' and try as hard as I can to do as little of it as possible. I've gone more than 100,000 miles on the factory brake pads on a couple cars in the past already, but much of that can be attributed to downshifting manual transmission vehicles - Using constant 'B' mode and touching the brakes as little as possible was an easy thing to learn, given my long history of using minimal friction braking

We still get typical RR's in the mid 70's, in urban settings with an occasional 80 to 85 thrown in when we make trips that involve little to no speeds above 50

Don

 

[MalcolmReynolds]

I get the impression from some of the replies in this thread that possibly there is some confusion about how hypermiling fits their own use in the city or urban setting. Some of the techniques here are applicable to all driving environments and others are specific to less city oriented driving. For example the tire pressure thing is a no brainer. I have been driving my vehicles at the max sidewall pressure for many years now. You will notice less rolling resistance, better economy, and you will get a lot better tire wear. Simple, safe, easy to do.

For the city driver you still can employ some techniques. Don mentioned don't be "that guy" who is on the brakes, hammer down, on the brakes from light to light. Hypermiling is driver awareness. Watching the traffic, watching the lights, give yourself space, smooth on and off the go pedal. Back off and regen or coast whenever possible. Many times this works very well when watching the traffic lights and timing them. Any time you can avoid coming to a complete stop and conserve any momentum you are going to save energy.

Unlike others here who seem to be concerned about the permanent state of angry distracted and nut case drivers on the road I personally ignore them now. I am going to drive my drive, not worry about the fact that the others around me are insane. I am going to back off early and roll/regen to the light, I am going to easy on the go pedal. I am going to try to avoid coming to a complete stop any time it is possible. If that means backing off really early when I can see the light has changed ahead of me "then so be it" that is what I will do and I will let everyone go flying past me. I will be in the "slow lane" and will be trying to stay out of everyone's path.

I don't just look at this as saving energy, extending range, but largely also the significant reduction in wear and tear on my vehicle. This applies to a ICE, PHEV, or BEV equally.

Also look around for routes to your destination that may be more conducive to your driving. Watch for elevation changes and try to see if you can use them to your advantage. For example many of the local businesses that I frequent for my shopping if I go one way there is a more gradual incline going to the stores, it is a main road with lots of traffic and higher road speeds. However there is another "back way" that is a much steeper climb going to the businesses that is slightly longer way to get there. However I found that by watching the energy consumption even though it is longer I can use that route going back home from the stores and it is largely a coast/regen most of the way home. Plus it is a slower set of side streets with less traffic.

So analyze your possible routes and just think it through. This all works very well for your local driving conditions for locations and areas that you travel often since you know the streets, the traffic lights, and exactly where you are going and where you need to be in the lanes to position yourself for turns etc. It is when you get into less familiar territory that you have to just be situation ally aware and adapt. These techniques are for everyone, not just BEV drivers.

After a while it becomes second nature and I can't personally fathom driving like everyone else. Every time I stomp on the go pedal or twist my wrist on my motorcycle I am very aware of it. It just doesn't make sense, never has, but we all just seem to want to go with the flow. The "flow" is how we got into this mess to begin with. Once you get beyond that "peer pressure" to conform you will stop worrying about what everyone else thinks.

My advice is to just try to stay over in the "slow lane" and let the congo line keep going past. I tell them if they don't like my driving stay off the sidewalk! LOL Most of the time you will see them again at the next traffic light and still just as "angry" as ever. It is their permanent state, don't take it personally.

Hypermiling is not only fun, safe, can save you some money, but you will save your car a lot of abuse in the process. It all adds up to a win for you if you can add some of these techniques to your skill set.

 

[FiddlerJohn]

I measured regen efficiency several times uses two i-MiEV cars. When the front i-MiEV, going 30 mph, uses 8 BARS (~7 kWh) the towed i-MiEV using regen B adds 4 BARS (~3.5 kWh). This implies the i-MiEV is about 70% efficient from battery to wheel/road, and the round trip back to the battery is about 50%. So regen cuts range like braking, but only cuts half the range as braking.

 

[Phximiev]

I measured regen efficiency several times uses two i-MiEV cars. When the front i-MiEV, going 30 mph, uses 8 BARS (~7 kWh) the towed i-MiEV using regen B adds 4 BARS (~3.5 kWh). This implies the i-MiEV is about 70% efficient from battery to wheel/road, and the round trip back to the battery is about 50%. So regen cuts range like braking, but only cuts half the range as braking.

"B" versus "Eco"?

 

[bradleydavidgood777]

To me this indicates that you lose efficiency using B or Eco mode instead of using D, N and light brake (charging only brake) appropriately and planning far ahead so that you can avoid braking at all if possible which gives you a full 100% efficiency rather than losing 50% every time you let off the accelerator in B.

 

[Don]

'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

 

[JoeS]

I personally find it impossible to keep my foot in that 'sweet spot' of zero power and zero regen, confirmed by using CaniOn.

There is no difference in the vehicle's energy consumption efficiency amongst D, ECO, and B. Any efficiency improvement comes from NOT using the brake, and in ECO the vehicle forcing you to drive efficiently by reducing the accelerator pedal input effect.

There is a more-nuanced portion to this discussion, which Aerowhatt and I have been debating for a year and which I am still trying to confirm. The premise is this: when in N the quiescent power draw of the car is less than when it is in any of the drive modes.

I love extremely-high regen (example: Bolt in L) and use B in both city driving and mountain driving; however, for the open highway downhill or coasting to that traffic light a block away I prefer zero regen and invariably pop the car into N.

 

[Don]

I personally find it impossible to keep my foot in that 'sweet spot' of zero power and zero regen, confirmed by using CaniOn

Keep practicing Joe - It's not that hard . . . . you'll get there eventually.

Note that the guy who did the 97 mile trip suggested using B mode was one reason he was able to make it so far, something most drivers don't seem capable of doing

https://www.youtube.com/watch?v=PWq304cPonM

. . . . . for the open highway downhill or coasting to that traffic light a block away I prefer zero regen and invariably pop the car into N.

Since the drive modes are electrically controlled, it shouldn't be that hard to put a switch on the gear shift knob to give you zero regen anytime you press it, no matter what drive mode you're in . . . . should it? That would be an addition we could all use. I love the max regen paddle in my Volt and I often wish I had a second one for no regen at all. Fiddling with the mechanical shifter to get me an electronic result seems so . . . . 20th century! :lol:

Don

 

[PV1]

Another complication with feathering the pedal at zero power is that the car moves the zero point dynamically with speed. If conditions allow, start down a hill at around 15 MPH, find zero power and hold the pedal steady. Watch the gauge move into Charge as your speed increases. The same happens, but adding motive power, as you lose speed.

I'd love to retrofit those paddles found in new JDM I-MiEVs into our current cars. I wonder how difficult it would be to add a switch to the wheel to put the car in neutral at any time, effectively adding a coast paddle.

 

[Aerowhatt]

'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.

 

[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
View attachment pict_2018-06-30_09-32-08.png
Using B full time for the run the result was 7.9 Mi/kWh
View attachment pict_2018-06-30_09-44-08.png
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.

,View attachment thumbnail-2.png

View attachment thumbnail.png

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 RRTG 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. :roll: :mrgreen:

 

[PV1]

Here are the numbers from this morning's drive in Koorz. I have a hard time believing this number, considering the car has not moved in the last month+ and I had low tire pressure. I wasn't even trying to hypermile, though I did deploy a few efficient driving techniques.

Thoughts?

 

[jray3]

Good job PV1, but since your average road speed was only 37 mph, I think the efficiency number is realistic.

 

[CZeroOwner]

Hey, the trip home is only 16 miles, so what's the problem?

Many thanks JoeS for reopening this topic. As you point out there are two factors that determine how far you can drive, the RR and the speed. The car tells us the RR but it doesn’t tell us at what speed that range can be driven. If you drive at a constant speed in the same direction on a level highway then after 15 miles the car computes the RR at that the car’s speed. If you change speeds then a process begins that recalculates the RR at the new average speed. This is also what you observed when the RR changed from 32 to 16 miles.

I had something a bit different in mind. I wanted to know how fast I could drive and still reach the next charging station. I figured that this would give the shortest overall travel time. To do this I needed the following numbers, the remaining kWh in the battery, the distance to the charging station and the watts at any speed. The remaining kWh is the SoC times the battery’s 100% capacity. I know the distance to the charging station. Computing the watts at any speeds requires a model of the car that computes the watts as a function of speed. I programmed this model into OBDZero. It is a textbook model that includes rolling resistance, drag and auxiliary watts. The last is e.g. heating. With this, the app finds a speed that gives the same kWh as that remaining in the battery. Here are the app screens.

At the start of a trip I enter the top number, the distance to the next changing station. While driving, the app re-computes this distance based on speed and time. The second number is the difference between the RR and the distance to the station. That’s the number you compute using your GPS. This is big help for me because I’m bad at doing arithmetic in my head. The bottom number is the speed the model suggests. I have used this function many times over the last 6 years and like you I have never seen the turtle while on the road. (But I have experimented with running the heater until the turtle appeared.)

To return to your point, It occurred to me that this Drive function could also compute the “hidden” speed behind the actual RR. The next two screens show the Drive function in this mode. When the distance to the next charging station is 0, the middle number is the RR. The bottom number is the speed that will result in the true rest range agreeing with rest range computed by the car.

I’m rather proud that my 2011 CZero still shows more than 100 km when fully charged. But there is a natural explanation. We have only driven 35000km. On the other hand the “hidden” or suggested speed is always low 30 - 40 km/h, when I first start the car. As soon as I get out on to the highway the RR drops quickly but the speed increases. After some miles on the highway the suggested speed and the car's average speed are more or less the same.

There are more details in the OBDZero user manual
https://obdzero.dk/wp-content/uploads/2022/08/OBDZeroUserManual38.pdf

 

[JoeS]

CZeroOwner, thank you for creating this unique approach. Sadly, in our heavy-traffic urban environment it is often difficult to employ hypermiling techniques without interrupting traffic flow. Case in point is simply coasting when seeing a red traffic light ahead will result in a half-dozen lane jumpers piling up in front (sigh).