Hypermiling the i-MiEV

[JoeS]

Jenn: OMG, that's frightening! Remember the warnings in the manual. Sounds as though their programming has a safety backup, but you don't want to test it
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:

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:

viewtopic.php?f=10&t=264

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

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:

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:

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

[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

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

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:
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.