Real world summer mileage expectations

[Kodawari]

Hello Everyone,
I have had my iMiev since April of this year and have spent quite some time reading the many articles on this forum (and learning a lot).
There has been much discussion about range and battery life and I would like some feedback on my summer driving experience. Lately, I have been zeroing the trip meter at every full charge to see how many miles I have driven before recharging. Not sure if what I am seeing is normal and would appreciate any feedback. Here is an example of today:
Started off with a full charge. The weather was very hot (over 90 degrees) and I was using air conditioning all the time the car was in use. I was able to drive 43 miles with the fuel gauge down to 2 bars. The 43 miles consisted of 21 highway miles between 50-60 miles per hour with the rest being local roads averaging around 35 miles per hour. For 25 of the 42 miles the car had four people on board. For the balance only two. The car was run in Eco mode the whole time.
Does 43 miles seem too low? Or, is this what other people are experiencing? I am thinking the car may not have made it to 50 miles before it ran out.
Just trying to get a sanity check here on the battery range.
Thanks for any advice you may have.
Matthew

 

[JoeS]

Hi Matthew, and welcome to the Forum. At 43 miles and two bars remaining, you'd just about hit 50 miles at 'empty'.

Without aircon and driving conservatively, your route description would lead me to expect about 7 bars remaining after the 43 miles.

However, there are too many variables -

Air Conditioning. Although not as bad as running the heater, I can see it alone easily destroying your range. It was a hot day (>90degF) and you ran the aircon for the entire trip (1 hour?) - offhand I'd point at that and say that's the culprit for this particular trip. Since we don't know how often the air conditioning cycles it is hard to quantify, but I'd guess a 25% hit in this situation would not be unreasonable.

Driving style - despite keeping the car in Eco, one can still get out of the green zone and override its benefits. Especially with a couple of passengers in the car, I tend to show off the iMiEV's peppiness and shoot my range all to hell.

Terrain - presumably flat?

Wind - any significant headwinds?

Tire Pressure - presumably at or above manufacturer's recommended 36psi. With four people in the car, this could easily hurt. You might try notching up the pressure a bit, say to 40psi, and see if it helps. I've noticed tire pressure loss over time on my iMiEV, perhaps attributable to the SE's alloy rims? - although I do admit to normally running excessively high pressure.

A couple of questions for you:

1. What was the RR reading when you first started the trip and turned on the aircon?

2. Normally, when you fully charge your car, what is the RR reading after it's charged?

 

[Don]

If you made this same trip in April with no A/C, how many bars would you expect to have left over after you got back home Matthew? Whatever the difference is, that's your A/C usage. It sounds like your last 2 bars would probably have taken you another 5 to 7 miles, for a about a 50 mile range in total

Assuming you had a few hills tossed in there, your trip sounds about correct to me. The A/C cost you a little, the miles above 50 mph cost you a little and if you had any hilly country, the 4 people in the car cost you a little - If you were 'demonstrating' the cars capability a little to your back seat passengers along the line somewhere, that cost you some too . . . . time with the needle out of the green Eco range always costs you

This is our second summer with the car (bought new a year ago May) and we regularly have summertime temps in the 90's here on the Gulf Coast, so we drive with the A/C on most of the time and I can easily make a 60 or 65 mile trip, though very little of that would be above 45 or 50 because we have discovered so many favorite 'shortcuts' which keep us off the freeways - Our trips probably average between 30 to 45 mph almost exclusively

I like to say you can make the car's range almost anything you like, if you are careful with speeds, acceleration rates and climate control usage. I drive exclusively in the B mode so that I get max regenerative braking all the time. Generally don't touch the brake pedal until below 15 mph or so and try to never let the red needle get above the straight up mark - Keep it in the green (and as low in the green as you can) as much as possible

Don

 

[Kodawari]

Hello Joe & Don,
Thanks for your quick reply. I collected some additional information that may help in answering your questions:
The winds were light the day I travelled.

There were probably a few mild grades on the highway but I would not say there were any "hills". I did try to keep the car mostly in the green zone but there were a few times on the highway that I needed to accelerate beyond that to maintain an acceptable speed.

I had just checked the tire pressures that morning and topped them all off to 36 psi. I have never considered running higher pressures. That is something worth consideration.

I did not check the RR reading the beginning of this days trip. However, I did check it on the way home. At that point I was one bar below the mid-point (on the fuel gauge) and the RR said 22 miles. I have found the the fuel gauge does empty faster on the bottom half of the "tank"(or is this just my perception). I had about 22 miles to make it home so perhaps I slightly beat the estimate?

This morning, after fully charging the car last night, I checked the RR reading and it was 62 miles. Immediately after turing on the air conditioning it dropped to 52 miles. So perhaps it is fair to say that running heavy air conditioning will cost ~ 10 miles off of whatever the planned mileage would be. I am not sure I can recall getting over 60 miles on one charge. This is why I am resetting the trip-meter each time now to see how I am tracking.
The RR number has varied quite a bit when charged. Perhaps I am just not being conservative enough with speed and accessory usage?

I am very encouraged on the 60-65 mile trips Don has achieved in the hot summer with air conditioning being used.

Don, I have a follow-up question about the use of B mode. Do you find this to be more economical in the use of battery charge than Eco mode? B mode still uses the same amount of battery power to move the car forward but has much more aggressive regenerative braking. Is not the savings in higher consumption to the drive motor in B mode not made up with the braking? Or does this really depend on terrain? I had thought the reduced drive motor consumption in Eco mode was more conservative even though it did not have as much regenerative braking. Really curious to hear your thoughts on this...

Another point I think you both have made very clear is speed is a big consumer. The lower the speed route that can be selected will make a big difference in battery consumption.

Thanks to you both for sharing your wisdom.

Matthew

 

[JoeS]

Matthew, I'll let Don answer your questions about B mode - it's a subjective preference. My comment is that you need to remember that any time regeneration kicks in and you don't need to slow down then that means that even though you are putting energy back into the battery it's not as much as you took out of the battery to get up to that speed in the first place.

If you really need to use air conditioning, you might check your aircon setting and maybe have it set to the minimum that's still comfortable in order to reduce its cycling. The ten-mile hit at RR=60 miles would probably be a five-mile hit at RR=30miles (i.e., it's a percentage and not an absolute number).

Yes, staying on back roads and avoiding the Interstate makes a BIG difference, as aerodynamic drag is the primary range-killer in the iMiEV. Just remember how hard it is to peddle a bicycle into a 30mph headwind.

Your fully-charged RR reading of 62 miles is somewhat low, as it should be in the 70's or 80's if you were driving conservatively for the last 15 miles before plugging in. You might review some of the hypermiling discussions on this forum; e.g., http://myimiev.com/forum/viewtopic.php?f=28&t=287 Incidentally, I've rarely, if ever, had the same RR number after a full charge - it DOES vary, and is simply a reflection of how one drove for the last 15 miles before plugging in.

I found it a pain to reset the iMiEV's trip meter and thus have installed an older Garmin 255W which has an instrument display which not only gives me trip mileage (easily resettable) but, if programmed for a destination, gives a continuous Distance To Go readout which makes it very handy to compare with the iMiEV's RR gauge.

 

[peterdambier]

Yesterday we got 133 kilometers or 83 miles, actually traveled some 80 kilometers.

It began with a short trip to an emergency med dusting a cabrio as soon as we got out of town and I grounded the pedal. Next came a visit to the city of Heidelberg spending more kilometers finding a parking not reserved or locked and then finding the right building of the hospital city and finding a way out of and through construction places.

I tried to conserve energy then because there are no sockets I can use and I dont even know where to find them. We did not use the refrigerator but I opened the windows sometimes at least. Above some 30 kilometers per hour or 20 miles it gets noisy.

Lots of traffic lights and roundabouts sometimes straight and 70 kilometers per hour or 45 miles and I did almost close the windows then. It was up and down hills sometimes flat. It was the same way back home. About half the travel was flat the other half was up and down hills. It was a good mixture of everything and top speed was 95 kilometers per hour or 60 miles per hour.

Temperature was 30 Celsius or 86 Fahrenheit. The hole thing was unplanned and badly prepared real life. We went some 80 kilometers and I would have done some 110 without headaches. I am sure the turtle would have got me 133 if not more.

Cheers
Peter and Karin (everything fine again)

 

[Don]

Don, I have a follow-up question about the use of B mode. Do you find this to be more economical in the use of battery charge than Eco mode? B mode still uses the same amount of battery power to move the car forward but has much more aggressive regenerative braking. Is not the savings in higher consumption to the drive motor in B mode not made up with the braking? Or does this really depend on terrain? I had thought the reduced drive motor consumption in Eco mode was more conservative even though it did not have as much regenerative braking. Really curious to hear your thoughts on this..

Matthew, I believe all 3 driving modes use the same amount of energy to get the car from a standing stop up to any given speed - There is no automatic 'savings' to be had using the Eco mode. It may be true that Eco does save a little if the driver isn't being careful, but if you're properly managing the Go Pedal you're not giving anything away by driving in either D or B. The B mode does require a bit more concentration to hold a steady speed without fluctuating in and out of regen, so it's not the best way for everyone

As Joe points out, anytime you come to a stop in any manner other than just coasting, you're unnecessarily losing some of the energy you used to get the car up to speed. This is especially true using friction braking, but even using the regenerative braking of B mode, you're probably only recapturing 2/3rds or so of the energy you would have wasted by using friction braking. Not needing to brake at all is best, but that's not always practical especially when driving in traffic

Best mileage is achieved by maintaining steady speeds, neither accelerating or decelerating. Going up small hills you can allow the car to slow just a bit, rather than pressing the pedal hard enough to maintain a steady speed going up and then you can very gradually regain the speed you lost on the downside of the hill and that will save energy

Your RR loss of 10 miles when you switch on the A/C after a full recharge is exactly the same thing I experience. Without using any A/C, 70 to 75 miles of range is achievable without too much trouble (assuming speeds of 30 to 45 mph) and you do lose about ten when you need the A/C

As you have already discovered, speed is the biggest range killer. The one time I made a trip completely on the freeway at a steady speed of about 65, I was shocked to see that 50 miles was really stretching things. That's when we began plotting 'shortcuts' which allowed us to drive slower and farther. Some of our 'shortcuts' really are shorter, but all of them allow us to drive farther than if we took the freeway to our destination

Even with all the stops and restarts of everyday city driving, the MPGe of the car is 126 city and only 99 highway - That gives you a pretty good indication of what higher speeds will cost you in range

Don

 

[DonDakin]

Hey all,

I thought I might chime in on this Imiev range discussion.

Range in the iMiev (or any EV for that matter) is really a function of how much you are in a hurry. I would also call that the root of
range anxiety. If your in a hurry and need to be on the highway then 50 miles is a good rule of thumb (with A/C) if your at 60 mph.

If you are not in a hurry and can drive slowly (30-40 MPH) and hypermile the car then 75-80 miles is a very reasonable number with the A/C on.

I concur with Don, all the drive modes (D,E,B) of the car are just aids to the driver to use less energy and recapture more of it for a given driving condition. These modes don't give you more range they just alter the speed profile to make it more efficient.

I think the drive modes are really great and I switch between them all the time.

IMHO The absolute best way to extend range is to plan charging at your destination. A simple 2 hour L2 charge will give you at least 25-30 miles in most cases. There is no driving technique that will give you that much range.

On a high mileage day if your not driving then you should be charging.

Don Dakin.......

 

[RobbW]

As Joe points out, anytime you come to a stop in any manner other than just coasting, you're unnecessarily losing some of the energy you used to get the car up to speed. This is especially true using friction braking, but even using the regenerative braking of B mode, you're probably only recapturing 2/3rds or so of the energy you would have wasted by using friction braking. Not needing to brake at all is best, but that's not always practical especially when driving in traffic

True, but if you have to stop (which you are required to do at red stoplights, lowered railway gates, or before running over a pedestrian), wouldn't it be best to use regen to capture back at least a portion of your energy use rather than simply coasting to a full stop? Coasting just prevents you from using energy, but it doesn't recoup any of it. When it's necessary to stop, I progressively use Eco and B to slow me down as much as possible, and the friction brakes only to come to a complete stop. Unless you're proposing not coming to a full and complete stop when required to by law, then I don't see how coasting to a stop is better than regenerative braking.

 

[Don]

Coasting is free mileage - You're making the best possible use of the energy it took to get the car up to speed, plus, many times if you see the need to slow or stop early enough, coasting might prevent you from needing to use any sort of braking . . . . the light may turn green by the time you get there, or the pedestrian may complete his crossing before he interferes with your momentum

True, if you must slow down faster than coasting to a stop, use of regen gets you back *something* whereas friction braking doesn't. If you prefer to drive it more like a 'normal' car and keep up with traffic and not coast up to every stop, then the extra regen of the B mode can provide significant savings over using the brakes, which is why I prefer to drive in the B mode 100% of the time

But still, best mileage happens when you accelerate and decelerate as little as possible - Add just enough energy to keep up your momentum, anticipate the need for any speed changes as far out as you can, decelerate a little going uphill and accelerate a little going downhill and you will find your total range improving as you get used to driving this very different car

Don

 

[fjpod]

As Joe points out, anytime you come to a stop in any manner other than just coasting, you're unnecessarily losing some of the energy you used to get the car up to speed. This is especially true using friction braking, but even using the regenerative braking of B mode, you're probably only recapturing 2/3rds or so of the energy you would have wasted by using friction braking. Not needing to brake at all is best, but that's not always practical especially when driving in traffic

True, but if you have to stop (which you are required to do at red stoplights, lowered railway gates, or before running over a pedestrian), wouldn't it be best to use regen to capture back at least a portion of your energy use rather than simply coasting to a full stop? Coasting just prevents you from using energy, but it doesn't recoup any of it. When it's necessary to stop, I progressively use Eco and B to slow me down as much as possible, and the friction brakes only to come to a complete stop. Unless you're proposing not coming to a full and complete stop when required to by law, then I don't see how coasting to a stop is better than regenerative braking.

yes...but any way you stop (except panic stopping with friction brakes), whether it be using the brake pedal, slowing down using B, E, or D, you will get the same amount of regen. The amount doesn't change, it's just that a slower or faster method may be better for the traffic situation you are in.

Ideal would be not having to use regen at all... that you could roll to a stop without having used so much acceleration that you need help stopping. This does not exist in the real world of driving.

I hear many EV and Prius drivers tell of how much they take advantage of regen braking. But this only means you have to accelerate again. It's only a second best scenario.

 

[Don]

yes...but any way you stop (except panic stopping with friction brakes), whether it be using the brake pedal, slowing down using B, E, or D, you will get the same amount of regen.

I disagree

A 'normal' (not a panic) stop using the brake pedal gives you some ratio of friction braking and regen, because the car automatically goes into regen when the brake pedal is depressed. The ratio in favor of friction to regen increases the harder you press the brake pedal, so as long as friction is involved, you're giving away some power. You certainly get more regenerated power back into the battery pack if you slow in B mode and don't touch the brake pedal at all until the car has nearly stopped using regen only. Anytime friction braking is involved at all, you're giving away (wasting) some power because you're not getting as much regen as you could be

Don

 

[RobbW]

Got it, Don. Thanks. I try to coast as much as is practicably possible. I understand the concept of free mileage. I used to coast as much as I could in my ICE vehicles, too. When anticipating a stop ahead, I will either let off the go pedal enough to balance between Regen & Eco (effectively neutral) or just bump it up into N. I will then coast as long as I can until I absolutely have to start braking. Then I drop it down into Eco to start the slowing process without freaking out the cars behind me. Then when I'm getting closer to the stop and the cars behind me have started braking too, I drop down into B for harder regen braking. At the very last moment, I will apply slight friction braking to come to the required complete stop.

 

[fjpod]

yes...but any way you stop (except panic stopping with friction brakes), whether it be using the brake pedal, slowing down using B, E, or D, you will get the same amount of regen.

I disagree

A 'normal' (not a panic) stop using the brake pedal gives you some ratio of friction braking and regen, because the car automatically goes into regen when the brake pedal is depressed. The ratio in favor of friction to regen increases the harder you press the brake pedal, so as long as friction is involved, you're giving away some power. You certainly get more regenerated power back into the battery pack if you slow in B mode and don't touch the brake pedal at all until the car has nearly stopped using regen only. Anytime friction braking is involved at all, you're giving away (wasting) some power because you're not getting as much regen as you could be

Don

It is my understanding, at least certainly with the Prius, that friction braking does not "blend" with regen braking. Friction kicks in suddenly during a panic situation or if you are crawling at less than 7 mph. I guess it could be different with the iMiev, but...??? So, is it published anywhere by MM?

Also, it is my unscientific observation that the amount of regen indicated on the dash, whether by brake pedal, or by drive modes, seems to create similar amounts of drag on the car. IOW, the dash indicates roughly the same amount of regen charge when you press firmly on the brake as when you shift into B. And, without going into panic stopping, the regen indicator indicates a higher re-charge the more you press on the pedal. So, the more pedal you use, the more regen you get. There does not seem to be a diminishing return by pressing the pedal more.

 

[fjpod]

Got it, Don. Thanks. I try to coast as much as is practicably possible. I understand the concept of free mileage. I used to coast as much as I could in my ICE vehicles, too. When anticipating a stop ahead, I will either let off the go pedal enough to balance between Regen & Eco (effectively neutral) or just bump it up into N. I will then coast as long as I can until I absolutely have to start braking. Then I drop it down into Eco to start the slowing process without freaking out the cars behind me. Then when I'm getting closer to the stop and the cars behind me have started braking too, I drop down into B for harder regen braking. At the very last moment, I will apply slight friction braking to come to the required complete stop.

I still maintain you get the same amount of regen by braking gradually as you do by using the various drive modes. It's kinda cool and convenient to do it with the stick sometimes, but it's the same as using the pedal judiciously. And the brake pedal gives the person behind you a signal.

 

[Don]

You can't tell too much about what's happening by observing the charge indicator on the dash because it pegs all the way to the left with only about 50 amps of regen . . . . but the regenerated power can (and does) continue to climb to over 100 amps even though you can't see any further increase on the gauge

I can see where this might confuse you to think that using some amount of friction braking still gets you all the regen possible because you can peg the meter to the left (50 amps) while friction braking (which might make you think you're getting all the regen there is to get) but you could be getting twice that amount (100 amps) by using the B mode alone and not touching the brake pedal

But - Even if 100% of the available regen could be had while friction braking, the length of time you're in regen would be shorter because of the friction slowing the car more rapidly than regen alone, so you'd still be missing out on some of the battery recharge you could be getting

It should be noted here that even more regen than the B mode is available by lightly touching the brake pedal just enough to turn on the brake lights, but not enough to begin any friction braking. The brake light switch engages maximum regen, but it's hard to hold the pedal exactly at that sweet spot short of friction braking because as the car slows and your body shifts forward, your foot just naturally presses a bit harder on the pedal. It would be nice to have an extra brake light switch in the form of a button atop the shift knob, so you could engage max regen (and turn on the brake lights) without actually having to touch the brake pedal

The friction brakes are fairly standard - Biased much more to the front discs than the rear drums - Probably even more so than on a normal car because the rear wheels are also braking with a considerable amount of regenerative braking, especially when engaged at high speeds

I know precious little about Priuses, but I see little similarity here between how the systems of a gas engine hybrid function compared to a fully electric car. On a Prius, any regen you get would be from the front wheels (because it's front wheel drive) so their friction braking is probably set up differently with less friction applied to the front wheels. For us, any friction braking means some amount of regeneration is being lost

Don

 

[misterbleepy]

I know precious little about Priuses, but I see little similarity here between how the systems of a gas engine hybrid function compared to a fully electric car. On a Prius, any regen you get would be from the front wheels (because it's front wheel drive) so their friction braking is probably set up differently with less friction applied to the front wheels. For us, any friction braking means some amount of regeneration is being lost

Prior to getting my Peugeot iOn, I drove Prius' for 8 years, so am pretty familiar with their braking/regen system.
Technically it is different, but maybe not as much as you'd think. While slowing down, either by lifting off the throttle or pressing the brake pedal, the ICE is disconnected and not using fuel, and so is pretty much out of the picture. Regen is used as much as possible before the friction brakes are engaged, even when the brake pedal is being used. It was very common (in the UK at least according to the user group I was a member of) for the front discs of a Prius to get heavily pitted due to rust formation and lack of use. This made it very easy to hear and feel when the friction brakes actually engaged - at 7mph and below, or if a fairly quick stop was needed.

What I find with this car is that it is very difficult to tell if/when the friction brakes are being used. Does anyone know for sure whether they are always used when the brake pedal is pressed, even if it is lightly pressed, or does it behave like a Prius and only use them if absolutely necessary?

My guess would be that they are always used, as the regen braking is done from the rear wheels, so there should be some front braking to maintain stability, and also if I look at my front discs, they are shinier than my Prius discs used to be (I live by the seaside, and salt is ever present...)

 

[RobbW]

I still maintain you get the same amount of regen by braking gradually as you do by using the various drive modes. It's kinda cool and convenient to do it with the stick sometimes, but it's the same as using the pedal judiciously. And the brake pedal gives the person behind you a signal.

I use the Eco and B modes' regenerative braking mostly out of preference. As you stated, it's cool and convenient to brake by the stick. I think it is awesome to be able to slow down without using the friction brakes AND regenerate a little power at the same time. Plus, it should extend the life of the brake pads, right? I remember reading elsewhere on these forums folks speculating on how long the OEM brake pads will last because of the regen braking. Someone even stated they wouldn't be surprised if they lasted 150K miles, although they also stated it was unlikely they would be around to see them last that long!

 

[RobbW]

It should be noted here that even more regen than the B mode is available by lightly touching the brake pedal just enough to turn on the brake lights, but not enough to begin any friction braking. The brake light switch engages maximum regen, but it's hard to hold the pedal exactly at that sweet spot short of friction braking because as the car slows and your body shifts forward, your foot just naturally presses a bit harder on the pedal. It would be nice to have an extra brake light switch in the form of a button atop the shift knob, so you could engage max regen (and turn on the brake lights) without actually having to touch the brake pedal

If lightly pressing the brake pedal turns on the brake lights which in turn engages maximum regen braking, wouldn't that mean it is just a switch? If it is just a switch, shouldn't some crafty person be able to wire up an accessory switch within arm or finger's reach that would perform the same function? If what you say is true, that it is the brake lights coming on that engages max regen, surely you should be able to wire a switch that manually turns on the brake lights, right? Or is it a mechanical process that engages max regen when you lightly press the brake pedal, and the brake lights only come on as a consequence of lightly touching the pedal? Meaning, the brake lights coming on really have nothing to do with whether or not max regen is engaged?

 

[JoeS]

Attached to the brake pedal is an encoder (potentiometer?) that provides a brake-pedal-position signal back to some computer. I believe it also feeds a rate detector which causes the brake system to apply serious braking if one "jams on the brake". Regeneration can be modulated using the brake pedal, which is why I *think* it is not a simple switch actuation. As an aside, on my Gen1 Honda Insight, the brakelight switch indeed activates regen, which varies with motor rpm.

Mitsubishi evidently worked long and hard at the seamless integration of regenerative and hydraulic braking, and, indeed, they've done it well as I simply cannot tell when the hydraulics kick in as the brake pedal is depressed - almost begs for a pressure gauge to monitor the brake hydraulics.

Don, I believe fjpod was referring to any of the various forms of regen application, including brakes before they engage the hydraulics - thus I think you are both in "violent agreement" with each other.

Back to RobbW's point: I've been toying with the idea of getting a brake-pedal-position encoder to see if a nice manual control could be developod - recall, my ideal is a steering-wheel mounted paddle that would allow variable-regen control. The new Smart ED has this as an option, but their paddle "shifter" only provides three discrete levels of regen (one of which is ZERO regen, which is great for highway driving).

Gawd, we got off-topic. Maybe move this discussion to a separate regen thread so we can find it in the future?