A Case of Diminishing Return

[jray3]

The compromise I'd prefer would be a battery that's normally charged to 80% or so, with a 100% SOC option to enable for highway trips, etc...

Well, that's exactly what the LEAF does, isn't it? Or is that your point?

For what it's worth, Mitsubishi has stated this feature would not have been worthwhile for the i-MiEV based on their battery chemistry and management system, implying that charging your i-MiEV to "100%" (or at least as far as it will charge) doesn't create the same level of problem as charging a LEAF to 100% (i.e., using the "full charge" option). While it wouldn't be a good idea to park the i-MiEV with 100% SOC for weeks, the normal ups and downs of nightly charging and daily driving shouldn't pose much problem, and we may be guilty of over-thinking things a bit in our attempts to improve battery performance. I suppose time will tell.

Guilty as charged! I want Mitsu to either warrant pack capacity (even if based upon some operating rules that the onboard computer logs could verify), automate an option for charging to less than 100% SOC, or explain why. Has Mitsu provided anything other than poorly translated or poorly spoken vagaries about their confidence in the battery design? I'm certainly more confident in their design than Nissan's, but lack the info to determine whether it's worthwhile to make effort for 80% charges (at a cost of deeper daily discharges and/or more frequent recharging).

 

[DonDakin]

Actually I think a slightly larger battery would be nice. But I agree a bigger battery brings problems.

Maybe 20 kW would be nice for the imiev.

If you look at old ev's with pbso4 battery's they were stuck at about 30 miles unless they were a truck. Li brings that up to 60-80 miles. Like tony said the next step is a lighter and more powerful battery to bring us up to 200 miles. When we get there I think we will have arrived.

But the real answer for the imiev is more quick charging, I could see an imiev easily doing 200 or 300 mile trips with enough chademo. Mind you 300 miles would add about 3 hours of charging to the travel time but considering the benefits of the daily 40 mile usage for me that would be fine.

But realistically if you want to do a road trip with more then 2 people you need a bigger car then an imiev. An imiev is really not for a family trip,more like you and the honey meander down secondary roads for a 5 day weekend.


I'm sure I will do some road trips in the imiev but only when there are many redundant chademo chargers in the area. To tell the truth I can't wait for that day to come.

But

In the meantime I check out plug share for possibilities and enjoy that little car every day.

Don.....

 

[Wulnoth]

At least I've got someone in my corner, DonDakin.

Don (The Mod) I know you know your stuff, I've read many of your posts here, but without involving in considerable calculation I dare to say that what is needed for a considerable increase in range would cost a great deal less than a 60kWh battery.

If you where to say that there isn't enough room for a large enough battery to give 150 miles range I would defer to your undoubted knowledge on the subject, but if there is room without a total re-design, any increase in battery capacity would render improvements over and above what might be suggested by ratio alone.

I think you would agree that battery weight alone would not be particularly range detrimental, I get much the same range per charge driving alone as I get when carrying two or three passengers, perhaps 5% difference in all.

I'm sure my passengers combined weight (approx 200kg) if translated into extra batteries would afford much improvement, I appreciate that I'm vastly over-simplifying things and not naive enough to think that such a rudimentary approach would work but I'm equally sure that a 60kWh battery wouldn't be needed.

The Tesla model S small battery model has a 60kWh battery and a range of 240 miles.
There are reports of a Nissan Leaf with 48kWh battery (ie. double capacity) I'm betting they get more than 200 miles range with that car, and both of those vehicles are significantly less efficient than the I-MiEV.

I understand that you believe you use the right vehicle for the journey (tool for the job) but I believe I can use an EV for all journeys, either with an electric infrastructure or with additional battery power, preferably both.

 

[Wulnoth]

Re Don's remark about not being able to use my I-MiEV with the same freedom as my Honda Legends before it, of course this was entirely predictable and I had hoped that the infrastructure in the U.K. would quickly allow unhindered roaming within our small island, indeed it did seem to be happening with the rolling out of a very usable CHAdeMO network, but just as the installation company was about to reach me, they suffered what appeared to be a viral fault which has set things back a year or more.

It goes without saying that without the infrastructure I would not be able to drive the two vehicles the same, but that remains my aspiration for EV's.

I think few of us want less from our EV's , we should want much much more, the only respect in which ICE cars might better EV's is being warmer, a sole advantage of the otherwise totally wasteful generation of heat.

 

[JoeS]

Our discussion has turned from having a car with sufficient battery size to meet most of our needs into explaining that in a few cases our perceived needs are a wee bit more than what we have. In my case, CHAdeMO would fill the gap; at the time I bought my iMiEV there were no CHAdeMO stations, but I'm pleasantly surprised at their proliferation. Hopefully Mitsubishi joins Nissan in installing them at their dealerships.

Instead of equating battery size with range, what about dramatically improving aerodynamics to achieve the same result with an existing battery pack? For example, there's VW XL1 (if only they would make this a BEV), Sim-Cel, Mitsu's CA-Miev, and a number of EVs from the X-Prize contest a few years ago that NielBlanchard had identified. I, for one, wish Aptera had come to fruition.

There presently is no ultra-aerodynamic BEV in production, with perhaps the Tesla coming closest - its low Cd is probably the main reason its range doesn't precipitously drop with high speed (like our i-MiEV). My Sparrow (similar configuration to that gas-powered Elio) does quite well from an efficiency standpoint (I have no idea what its Cd is), but I haven't bothered to fully populate any of my Sparrows with Lithiums to get to 100 miles.

 

[Don]

I think you would agree that battery weight alone would not be particularly range detrimental, I get much the same range per charge driving alone as I get when carrying two or three passengers, perhaps 5% difference in all.

Actually, that was a large part of the 'Case of Diminishing Return' this thread is all about - The other part was the high cost of battery power to get the extra range and then using that extra power less often . . . . a poor return on your investment

But you want to have your cake and eat it too - Triple the range, no significant extra weight and all for only 5,000 pounds!!

The 60 Kw Tesla gets 3.5 miles to the Kw and the heavier 85 Kw car only gets 3.1 miles to the Kw which is a loss of more than 10% . . . . not the 5% you mentioned. This was adding about 1/3rd more pack capacity, which only increased the range by 1/4th

You are suggesting a larger battery for your iMiEV which would increase the range by 3X, so the weight differences would be even more dramatic than with the Tesla, and since it would require major changes to the car (you are correct that using existing technology, it wouldn't even fit, let alone addressing the dramatic weight difference) so the $10K extra Tesla charges for the upgrade would be a drop in the bucket for the costs to make an iMiEV a 200 mile car

It's just the wrong car to begin with. It's not a touring car, it's a city car. It will go 80 miles per hour, but it's not fun to drive at those speeds on the freeway with the wind buffeting you get from larger vehicles. If you truly want/need a 200 mile car, you should begin with something better suited to that type of usage, IMO

Again, buy what you need, but not more - Going 'overboard' with an EV is both costly and not a good return on your investment. Your proposed 200 mile iMiEV would easily double it's price and you'd still have what is basically a $12K 'econo-box' . . . . but you'd be spending near Tesla money

Don

 

[Don]

Instead of equating battery size with range, what about dramatically improving aerodynamics to achieve the same result with an existing battery pack? For example, there's VW XL1 (if only they would make this a BEV), Sim-Cel, Mitsu's CA-Miev, and a number of EVs from the X-Prize contest a few years ago that NielBlanchard had identified. I, for one, wish Aptera had come to fruition.

There presently is no ultra-aerodynamic BEV in production, with perhaps the Tesla coming closest - its low Cd is probably the main reason its range doesn't precipitously drop with high speed (like our i-MiEV)

I doubt you'd get more than a 10% to 15% increase in 'real world' range just by minimizing the Cd of the car as much as possible, but in the process, you would certainly sacrifice much of what many of us bought the car for - The utility of the current design. It's easy ingress and egress, it's relative comfort for 4 adults, (my brother says our car has 'the most comfortable back seat he's ever ridden in') it's ability to haul significant cargo with the seats folded down, it's short overhangs on both ends which make city parking a breeze. I think major changes to the body configuration would be less practical at adding extra range than adding another 8 Kw or so to the battery pack . . . . and the body changes would probably cost more and would certainly make the car less useful

I think that in order to see even a 10% increase, you'd have to do your testing mostly at higher speeds, where the Cd really comes into play. Driving it around at 30 or 35 mph like many of us do, the increase would likely be more on the order of 5% (just my guesses, mind you) and I for one wouldn't consider giving up the utility that would be lost for the small increase in range. I'm sure others opinions will vary, but I bought the car in a large part because of it's utility - I would not have even considered the purchase if it had been a sleek sporty design with an 75 mile range opposed to the current 62 (which would represent a 20% increase . . . . very hard to do I think) if it meant living with a back seat suitable only for small children, a reduced cargo capacity and an extra foot and a half of overhang

Don

 

[JoeS]

Don, of course we have to preface any discussion by identifying the driving scenario. Around here, especially when commuting, one usually spends about five minutes on city streets and then hops onto a freeway and then roars along 10-40 miles and then spends another few minutes on city streets after getting off the freeway. Freeway/Interstate speeds mean rarely going below 55mph, even in the right lane.

Since I'm no longer a commuter, my i-MiEV satisfies almost all of my local needs which on average I would say are a 50/50 mix of city streets and freeway driving. What I'm now looking for is a very efficient long-distance car to replace my Insights, but, as you point out, without over-buying battery capacity which would rarely be used. Ballparking numbers, I would say that our i-MiEV's 70mph usable range is about 50miles whereas it's 40mph range is easily 75miles, a 50% improvement.

 

[Wulnoth]

O.K. Don,

I didn't realize that you were on a crusade here, I am merely expressing the wish for slightly more range.

I did say 150-200 miles would be nice but you keep quoting me as saying 200 miles and three times the capacity.

As for losing 5% when carrying passengers, I drove two friends around a couple of days ago, I drove thirty six miles with forty four miles remaining which from experience is little different from driving alone.
I'm not hell bent on converting anybody else, it's just that without the infrastructure vehicles with slightly more range will go a long way to make EV motoring meet my total requirements, of course I also hope for the infrastructure.