Hypermiling the i-MiEV

[JoeS]

Jenn: OMG, that's frightening! :shock: Remember the warnings in the manual. Sounds as though their programming has a safety backup, but you don't want to test it :evil:
I always push the lever to the right when going up into N from D.

To answer rokeby's ScanGaugeII question: I tried hooking mine up and it never connected but just kept trying...

 

[NeilBlanchard]

Joe,

I think your posts on regen and hypermiling are spot on, and I agree with you on almost all points. But I think that it is quite possible to improve the aerodynamics with modifications. Smooth wheel covers and rear wheel skirts and a Kamm back would be the first things I'd recommend.

There is a thread started for a more involved mod which would be to build a boattail that doubles as a storage trunk:

http://myimiev.com/forum/viewtopic.php?f=14&t=326

Truth be told, I don't own an 'i', but my brother is buying one. I will be kibitzing with him, for sure.

 

[JoeS]

Neil, welcome to the myiMiEV forum. I recall all your wonderfully-informative posts on the Aptera forum.

Thank you for the update about the boat tail. We also have a thread on drag coefficient:

http://myimiev.com/forum/viewtopic.php?f=10&t=264

Where jray3 already posted a great picture of a Gen1 Honda Insight with a nicely-done extension:

http://myimiev.com/forum/viewtopic.php?p=2189#p2189

We're also waiting for oahumiev to let us know how the airtabs turned out.

I've already made a cardboard cutout for an iMiEV wheel skirt, but hope to get down to the local plastics shop to see what they have or else I'll make a couple of skirts out of carbon-reinforced doorskin. I already have a clamp arrangement in mind, but it's all a work-in-progress with other priorities...

On this thread, for now I've been holding off addressing the iMiEV's biggest range deterrent (poor aerodynamics) ... didn't want to get into the whole discussion of drafting and what is 'safe' vs. dangerous.

At the bottom end of the scale, I've made some amazingly-low low-speed energy consumption measurements, which I have yet to publish on this thread:

http://myimiev.com/forum/viewtopic.php?f=10&t=391

People are finding out just how difficult it is to get a windless perfectly-level stretch of road and be able to take power-level vs. speed measurements.

Elsewhere, made some current measurements which show that the iMiEV's max regen is over 100A, with a max power current draw being a little over 150A:

http://myimiev.com/forum/viewtopic.php?f=10&t=288

For me, this will all have to wait, as we're leaving town for a few weeks... hopefully I'll still find connectivity.

Once again, welcome.

 

[NeilBlanchard]

Thanks for the welcome! He actually picked his "raspberry" 'i' up last night, and got to drive it to and from work today.

He's still feeling out the regen situation. He has a fair bit of time in driving his wife's Leaf, so I'm sure he'll do fine.

 

[Andros99]

This is the exact case with the Prius too (I own one and have the most popular mypermiling
vid on youtube) I'm ordering my Imiev in two weeks.

So, here is my answer. To make it easier to hold your foot in the no-regen spot, It would be
really cool to have a soft detent spot there (in the pedal travel). This can be accomplished by mechanical means.
Alternately, a tactile vibrational feedback on the pedal would be perfect. It would softly vibrate right at that position.
This would be accomplished by using IR LED sensors and a Cell phone vibration motor. That's safer than a mechanical system.
You don't have to look at the gauge and it trains your muscle memory as to where the sweet spot it.

Regen is useful over a certain angle of decline on the road. That's the spot where regen doesn't slow you down.
An indicator to show you what that angle is- would be comprised of a two-axis accelerometer and either
schmidt trigger comparator or a full-on microcontroller driving LED's. It's actually a simple project.
It's really that no battery chemistry can efficiently take a charge in such a short time. Ideally, this would be handled
by super-caps. I have no idea why nobody has done this.

I'll be showing plans for a Level 1 solar charging system and and elegant rear-end collision avoidance system in the next 4 months.
The above items may find their way here too.

I'm getting excited!

Bob-Hot Springs :mrgreen:

 

[JoeS]

This is the exact case with the Prius too (I own one and have the most popular mypermiling
vid on youtube) I'm ordering my Imiev in two weeks.

So, here is my answer. To make it easier to hold your foot in the no-regen spot, It would be
really cool to have a soft detent spot there (in the pedal travel). This can be accomplished by mechanical means.
Alternately, a tactile vibrational feedback on the pedal would be perfect. It would softly vibrate right at that position.
This would be accomplished by using IR LED sensors and a Cell phone vibration motor. That's safer than a mechanical system.
You don't have to look at the gauge and it trains your muscle memory as to where the sweet spot it.

Regen is useful over a certain angle of decline on the road. That's the spot where regen doesn't slow you down.
An indicator to show you what that angle is- would be comprised of a two-axis accelerometer and either
schmidt trigger comparator or a full-on microcontroller driving LED's. It's actually a simple project.
It's really that no battery chemistry can efficiently take a charge in such a short time. Ideally, this would be handled
by super-caps. I have no idea why nobody has done this.

I'll be showing plans for a Level 1 solar charging system and and elegant rear-end collision avoidance system in the next 4 months.
The above items may find their way here too.

I'm getting excited!

Bob-Hot Springs :mrgreen:

Hi Bob, you've included a number of interesting ideas and comments -

Re: no-regen spot detector/notifier. Yes, the concept you outlined would certainly work. For myself, I just throw the iMiEV into neutral many many times throughout a typical drive (I'm used to driving a stick shift).

Re: road slope detector. Without the front hood, I still have a problem detecting subtle slope changes. When my wife is with me, we run a program called Motion-X GPS HD on the iPad which give the percent slope. Unfortunately, it has a time delay of quite a few seconds. On an Interstate downslope of ~2%, my Gen1 Insight can maintain ~65mph in neutral; however, the iMiEV noticeably slows down in the same situation. Gotta fix that Cd!

Re: rapid battery polarity reversal and supercaps. If I recall reading, there have been several experiments using supercaps in parallel with the batteries to provide the instantaneous power or energy absorption (sorry, don't have the links). What you said about batteries' inability to instantaneously recharge efficiently has me intrigued, as our iMiEV drops into regen hundreds of times during a typical drive, and I've measured regen currents of over 100A. I have had my fuel gauge go up while regenning on long downslopes.

Good luck with your new iMiEV and I'm sure many of us are interested in hearing about your projects,
JoeS.

 

[jray3]

Regen is useful over a certain angle of decline on the road. That's the spot where regen doesn't slow you down.
An indicator to show you what that angle is- would be comprised of a two-axis accelerometer and either
schmidt trigger comparator or a full-on microcontroller driving LED's. It's actually a simple project.
It's really that no battery chemistry can efficiently take a charge in such a short time. Ideally, this would be handled
by super-caps. I have no idea why nobody has done this.
Bob-Hot Springs :mrgreen:

Maybe it's because we could just stick one of these to the side window and glance at it when speed is steady....
http://www.tiltmeter.com/basic_models.html

 

[JoeS]

I had a EUREKA! moment at some point in my 11-hour drive up to the Sierra foothills on Christmas Day. It has to do with maximizing the car's range while going downhill. Let me explain…

As some of you may have read earlier in this thread, I am a great proponent of coasting wherever possible: after all, what is more efficient than a vehicle moving while consuming zero energy? This all stems from my Gen1 Honda Insight ICE/hybrid hypermiling technique whereby every downhill has me putting the car into neutral and shutting off the fuel injectors as the car roars down the hill (this is safely done in this particular car because the engine automatically restarts if needed). With the i-MiEV I continued this routine: most of my everyday downhills are shallow and the car coasts nicely down the hill while maintaining the speed limit.

Well, this Christmas Day marathon drive made me think about the optimization of RANGE rather than simply conserving energy. The scenario is a traffic-free country highway where one gets to a 6% downgrade that lasts several miles.

In the past, I would simply kick the i-MiEV into Neutral and let it happily roar down the hill, its aerodynamic drag limiting the car's maximum speed.

Now, I got to thinking, what if I tried to scavenge some of the car's kinetic energy instead of letting aerodynamic drag do that? So, rather than letting the car get up to 65+mph while coasting, I now simply engaged D-E-B to keep the speed down to about 35mph. As with many downhill runs not in Neutral, this often added enough charge to the battery pack for the fuel gauge to go UP, which simply coasting would not do. In either case, it's always nice to see RR increase despite the car having travelled a bunch of downhill miles.

Just another controlled test needing to be run, with CaniOn providing quantitative information. Anyone care to do the math ahead of time?

Edit: I just re-invented the wheel as we already have a thread on just this topic:
http://myimiev.com/forum/viewtopic.php?f=28&t=1685

 

[NeilBlanchard]

Joe, I think your method works in situations with a steep hill and long enough to do this, and/or where you have to stop at the bottom anyway. And if, you are far enough into the drive to be able to "fit" it into the battery.

 

[PV1]

Joe makes a lot of sense. Instead of burning off extra energy into moving air, put that energy in the battery instead. After all, air resistance is our number 1 energy consumer. If traffic permits, I try to put the car in neutral before the top of some hills so I can coast and gain speed on the downhill, then I drop it back into gear to regen as I approach the speed limit.

I have a lot of fun driving back from the annual Mother Earth News Fair. The trip out really tests my hypermiling skills. It's only 56 miles, but I have to climb two mountains to get there. The first year, I let the car fully charge for my trip home, not thinking that regen's reduced above 85%, let alone 97% charge. I started down the first hill (which is the steepest), dropped the car into B mode, and....nothing. I was sailing down the hill at 50 mph with almost no regen! That was one of the few times my friction brakes actually got used. So, being cold and damp from the mountain rain, I turned the heater on full blast, which didn't help as much as I hoped. I shut the heater back off since I was now at the bottom and had to give near full power to get up the next hill. Then it leveled out for a while until I come up on "Three Mile Hill". Going down this hill is the first time I've gained a bar while driving. With a 35 mph speed limit, I could go down the hill in ECO with no pedals and maintain speed. This year, I stopped the charge at 92%, which helped with the first hill. I was able to hold back with regen for a little bit before it starting cutting back. I was still cruising when I hit bottom, though.

 

[DogMan12]

I coast and manage hills on my daily commute, and usually consume one bar for the 16.5 miles inbound with a net elevation loss of 1,300 feet. It takes 6 or 7 bars to get home.

WHEN THERE IS NO ONE ELSE ON THE ROAD I accelerate gently on the downslopes and coast on the flats and even many uphills. My speed varies a lot, from 30 to 50. WHEN THERE IS TRAFFIC I coast downhill and power uphill, maintaining no more than a 5 mph variation in speed, +/- 2.5 mph of the speed limit.

I actually do the same things in my ICE commuter, and have achieved 45-50 mpg overall in a car rated at 37 mpg.

There is no way around the physics of work. Acceleration is work. Press the go pedal like there is a raw egg between it and your foot, and you will be efficient even without radical hypermiling techniques.

 

[jray3]

DogMan, sounds like we have a similar commute, though I only have 525 feet of net elevation loss over 16 miles. I agree with these points. Even on a 6% downslope it's hard to coast past 65 mph. If you've got the time and won't hold back traffic, regenning down the mountain at slow speed would yield dividends. Here's a post with mountain road trip details.
http://myimiev.com/forum/viewtopic.php?f=9&t=1177&start=10&hilit=Leavenworth

 

[DogMan12]

None of my grades are steep or long enough to get much out of regen without slowing down below 30, which even for me is too slow. I don't mind taking 26 minutes, but that is about as long as I want to take on the road. At .09/kwh, getting deep into the last 5% of efficiency is just about bragging rights on forums, ( :lol: ) not about any significant savings.

 

[JoeS]

As you read the previous posts on this thread, you can see that I abruptly stopped the discussion before addressing the key i-MiEV range-robbing element: aerodynamic drag at speed.

The solution is elementary: have some large vehicle push the air aside and then follow it. The range-increasing results are dramatic! This graph http://myimiev.com/forum/viewtopic.php?p=17565#p17565 needs no explanation - imagine traveling at 60 mph while only facing an effective headwind of, say, 30 mph: from the graph, instead of a range of 50 miles at 60mph we now get a range of 100 miles!

No, I'm not advocation NASCAR-style drafting, but a significant benefit can be derived from following large vehicles, yet at a distance that allows for taking evasive action in emergencies.

As some of you might recall, last June while traveling on Interstate 5 in my Gen1 Honda Insight I was hit from behind by a drunk driver. Before the accident I had been safely following a huge truck for a couple of hundred miles but, unfortunately, the truck had just turned off the highway and I was left nakedly exposed continuing down the highway at 60mph (the speed limit for cars on this very long and straight Interstate is 70mph), of course in the right lane. Within a couple of miles I got whapped as this drunk veered from the left lane into mine while traveling at what I estimate to be >100mph. The string of cars in the left lane was passing me going around 70mph and this driver came upon them quickly and suddenly veered into the right lane not seeing my small car there. I'm happy to be alive, but this incident got me thinking about the whole issue of efficient driving, visibility, and safety.

Following trucks has the major disadvantage of one not being able to see the road ahead, which means that road debris can unexpectedly and unavoidably suddenly appear from under the truck. Sadly in recent years, this is also a peril for all small car drivers as SUVs and pickup trucks have proliferated the landscape. This is also the major hazard motorcyclists face on a daily basis.

The other traditional concern of following trucks too closely simply doesn't apply: barring a sudden-stop accident by the truck ahead and given reasonable responsiveness by the car driver, in an emergency the car will stop much faster than a truck.

In California, multi-axle trucks have a speed limit of 55mph, which means that they usually travel at 58-62mph, a speed that is just fine for covering longer Interstate distances in our i-MiEV. Based on my own recent experience described above, the major advantage of driving at 60mph and following a truck is that the truck offers a visual barrier to anyone coming up quickly from behind.

When following trucks or other large vehicles, each of us must decide for ourselves what the comfortable and safe distance is for that particular scenario. For example, I do try to avoid situations whereby I'm sandwiched between trucks, and instead prefer just tagging along behind a solitary big rig.

After three years of driving my i-MiEV, I must say that I've rarely employed this range-maximizing technique. Almost all of my driving entails highway trip distances of under 60 miles, which the i-MiEV does comfortably without resorting to extreme hypermiling. It is only the occasional extended trip between sparse recharging opportunities which benefits from having this ace up my sleeve, if needed.

 

[RobbW]

I have been intrigued reading through this thread on hypermiling our iMiEVs. JoeS, you did an awesome job with all your pointers! I so wish I could employee these hypermiling techniques. Alas, I live and commute in suburban Chicagoland with too much traffic to employ most of the techniques and not enough topographical change to take advantage of coasting/regenning down hills/mountains and such. My biggest obstacle with employing any hypermiling techniques during my normal commute is other drivers. I don't want to piss off any of my fellow commuters.

I have to deal with typical Chicagoland drivers with their complete lack of any patience and usual "screw you" attitudes. Anything I do in my Meepster that would slow down the flow of traffic is going to put me on "The List". And since I usually drive the exact same route at the exact same times of the day every day, I'm usually driving with the exact same drivers every day. So, I don't want to become known as "That Guy" whom everyone else constantly tries to beat out and gets all pissy when the end up behind me.

I'd be happy to read anyone's tips, techniques, advice and recommendations for hypermiling in urban/suburban commuting environments. Or is any potential gain from hypermiling too insignificant to be worth the effort and the ire of fellow commuters?

 

[JoeS]

...I'd be happy to read anyone's tips, techniques, advice and recommendations for hypermiling in urban/suburban commuting environments. Or is any potential gain from hypermiling too insignificant to be worth the effort and the ire of fellow commuters?

Robb, I hypermile my Gen1 Honda Insight to save gas (the one that was crunched had a lifetime 77.0mpg over 95K miles). When I first got the i-MiEV, I continued with my hypermiling kick (to save on energy and not stress the motor and battery pack) until I slowly came to the realization that I don't need to do that, except on long trips where I'm stretching the range. With my fully-amortized PV solar, my electricity is free, and the motor and battery management simply won't let me overstress those components (but I never run my battery down low, and I become a featherfoot at about 3 bars). On a daily basis I have now reverted to my old leadfootin' ways and, especially during rush hour traffic, I 'go with the flow'. In your case, and since you're not pushing your range limits during your commute, I think the only benefit would be a negligible financial gain, which I do not think is worth the effort or "ire of fellow commuters", as that would result in their looking askance at EVs.

That said, hypermiling is a skill that belongs in everyone's toolbox, as there will be occasions when one needs to eke out a few more miles...

 

[jray3]

I don't want to become known as "That Guy" whom everyone else constantly tries to beat out and gets all pissy when the end up behind me.
...Or is any potential gain from hypermiling too insignificant to be worth the effort and the ire of fellow commuters?

Well, I'm also swimming with the same fish often, and besides being the only i-MiEV in my neck of the woods, MR BEAN is somewhat conspicuous, with the personalized plates and big 8-ball emblem up top. I employ regen to slow down waay before red lights, but then rocket through the intersection as the light turns, while the bozos who impatiently passed me are sitting still at the start line. I swear that I've seen some beneficially-modified behaviors from individual drivers after they pass through several such intersections with me... Plus, I haven't been coal-rolled yet, unlike another here.

Thing is, my commute is short enough to drive it like I stole it, so my technique tends to be more about 'winning the race' rather than true hypermiling!

 

[JoeS]

WARNING
After failures of my Yokohama tires, perhaps the result of my previous tire overinflation, I wish to emphasize that the manufacturer's specification is 36psi. Please take this into consideration when reading my previous discussions on tire pressures.
http://myimiev.com/forum/viewtopic.php?p=24356#p24356

 

[JoeS]

So, the question on the table is "how do I know I'm hypermiling successfully?".

Let's see,

1. When fully recharging the car after a drive on level ground in average temperatures and not much wind, the Range Remaining (RR) is > 85 miles (137km).

2. When you first set off with a 'full tank', you go at least ten miles (16km) before the fuel gauge drops from 16 to 15 bars.

3. While driving, the fuel gauge is at the halfway mark (8 bars) and RR reading is >45 miles (72km).

4. After driving for a couple or three hours and the car stops inexplicably, you realize you've just driven over 100 miles (160km) without looking at any of the gauges…

 

[RobbW]

So, the question on the table is "how do I know I'm hypermiling successfully?".

Let's see,

1. When fully recharging the car after a drive on level ground in average temperatures and not much wind, the Range Remaining (RR) is > 85 miles (137km).

2. When you first set off with a 'full tank', you go at least ten miles (16km) before the fuel gauge drops from 16 to 15 bars.

3. While driving, the fuel gauge is at the halfway mark (8 bars) and RR reading is >45 miles (72km).

4. After driving for a couple or three hours and the car stops inexplicably, you realize you've just driven over 100 miles (160km) without looking at any of the gauges…

Sadly, I don't meet any of those criteria. I just don't drive in an environment that is conducive to maximizing any hypermiling techniques. I do what little I can when I have the opportunity.