Phoenix Range Test Sept 15, 2012 planning!

[spooka]

Thanks Tony for all the effort you put into getting this test implemented. Thanks also to the others that were up all night getting the cars ready and everyone that volunteered their Leaf and time for the cause. When I arrived in the morning, everything was set up efficiently and ready to go. Quite impressive. I am disappointed at the "nudges" ITT that weren't there criticizing the effort because apparently testing wasn't performed under perfect laboratory conditions. I am in the medical field, I have seen/reviewed many clinical trials and I can tell you that Tony got this as right as anyone could have with the time constraints and multiple issues that needed to be dealt with.

I just dropped my Leaf off at the dealer for my battery test. The tech told me I would receive capacity data in the report I get tomorrow when I pick the car up. He said it is quite in depth. We'll see. All questions I had about capacity and names of people I could speak with about this were pushed off by the tech. He did tell me he thinks this is a heat related issue. I was surprised to hear that type of statement from him.

Thanks again Tony for not wasting my time. I put myself and my family up in a hotel overnight to be able make the test and it was worth it just to see you pull this off! WOW

 

[MrIanB]

If I lived within range I would have been there in a heartbeat but, Austin Texas is toooooooooo far to reach. Lol

Ian B

 

[TonyWilliams]

 

[azdre]

Who is who?

I'll 'out' myself, opossum on the far left, azdre hiding behind him.

 

[edatoakrun]

Not a "smoking gun", but a significant and avoidable source of inaccuracy, IMO.

I guess it depends on what range effects you consider "miniscule"(sp). Do you disagree with the opinion I posted last night?

...If they all had 6 bars on the battery temp gauge, I doubt you could have had more than ~20 F variation in battery temperatures at the times the charges were completed.

No one, AFAIK, has accurately calculated how much more capacity the batteries have (assuming the BMS does not intervene at some higher temperature) when the battery temperature is increased this amount, but I think most would say this is probably no more than 2% to 3%. Not huge, but probably quit a bit more significant than the accuracy caused by the variable levels your windows are open while you drive, or for that matter, whether your tires had 36 or 40 lbs of pressure.

A simple way of avoiding most of this inaccuracy in future "mass" tests might be to charge the entire "fleet" to anywhere from 80% to 95%, let the temperature normalize to near ambient (overnight, in your situation) and top them off just before the test.

You know.... 2% of 80ish miles max range is.... wait for it... 1.6 miles!

1.6 miles is significant? When we are seeing overall ranges between 50 and 80 miles or so?

Tony, you know what? You also forgot to make sure the wind was consistently 6MPH from 5 degrees East of North by altering the route dynamically throughout the morning to compensate. Dang! How could you have missed that?

edatoakrun, with respect, enough of this. You missed your opportunity to comment on the particulars during the 1.5 weeks that Tony had his proposal out and during which the rest of us made contributions to it. It's a little late for doing so now. He covered far more variables than most of us would have even considered I think.

Actually I did comment, on page 28 of this thread.

I mentioned the battery temperature only as a factor for the recharge capacity test, since It did not occur to me that anyone would do a range test and not try to control for battery temperature variations during charging.

Good to see thes (sp) range tests planned. I have been conducting range tests of my LEAF, and suggesting how useful they are to all LEAF drivers, for over a year now.

You are planning to monitor your recharge capacity after the range tests, I hope?

I haven’t seen much mentioned about this on this thread.

If you monitor the recharge, you should be able to determine accuracy of the the two m/kWh reports from each LEAF (and the battery capacity value they are calculated from), the KWh use as reported by carwings, as well as the values in Wh of each gid, or (lost) capacity bar in your LEAFs.

If you control for battery temperature, The only variables on the recharge I can think of would be BMS operation (if the”100%” charge level allowed is different from the previous “100%” charge level) and variable charging efficiency, which probably will vary with battery degradation.

In fact, relying on memory rather than written records of an earlier test's recharge led me to make a similar error in one of my range tests last Spring, as I posted at the time:

...About another 6,500 miles and nine months after my first range test, and after repeated tests in different conditions, I feel certain that my capacity loss is fairly small. Perhaps the largest variable remaining, is battery temperature when charging. Unfortunately, IMO, we have not gathered sufficient data to understand the larger amount of total battery capacity accepted by a warmer battery, and how much, and at what high temperature, the total charge may begin to be limited, temporarily or permanently, by the charge management system.

(And later, I mentioned my error)

...Oops.

My other observations have led me to believe that this cooler ambient charge temperature might be expected to reduce kWh capacity by about (?) 3%, so my total loss could be more like 3%, more or less, with the many other unknown uncertainties. I have several reports of 60-something F ambient charges, leading to 17.-something kWh capacity, but have none at a significantly higher temperature, since last summer.

I probably will try one more test, when the temp get back to the 90’s, and then wait till later in the day, to charge to 100%...

http://www.mynissanleaf.com/viewtopic.php?f=31&t=9064" onclick="window.open(this.href);return false;

IMO, the uncertainty in the results caused by battery charging temperature variations did not invalidate my range test of last Spring, and it does not invalidate the results from the Arizona test run on Sunday. But we cannot develop better test protocols for future efforts, without discussing the ways previous efforts could have been improved to increase accuracy of the results.

You can learn from your (and others') mistakes, or you can repeat them.

Your choice.

 

[EatsShootsandLeafs]

I think temp while charging is important and it affects capacity, but that this is an issue best left for Nissan's engineers to consider when they have a lot of time and need to gather a lot of data-- enough to influence product development and software.

The intent of Tony's study is to simply identify if range of bar-depressed Leafs is impacted and approximately to what degree; I.e. are all the heretofore stated estimates generally accurate. All variables affect the study but not all change the meat of its conclusions.

------------

Tony when the results are ready I hope you create a new thread, one about the findings whereas this one is more about the prep work of the event.

 

[vrwl]

Who is who?

I'll 'out' myself, opossum on the far left, azdre hiding behind him.

Those of us who watched your local news video have seen both opossum and Scott Y previously, so when I saw the pics, I thought it was opossum, and then of course, you were the only female there, so I had to assume it was you since your car was one of the ones tested. Great work to all, many thanks for the hours and hours of work, the dedication to the cause, and the great amount of thought put into this range test. It is much appreciated.

 

[EVDrive]

Some person on this thread is getting annoying. The temp the temp. Yes we get it. You made your point 20 times.

I disagree about the utter importance of having every car charged at the same temp. Sure it would be nice but nobody is so ocd, i hope, that they would not charge their car until it was stored in a cooler first. This is a test of how heat and time impact battery life and range in the real world. This is not a test of what a leaf can do in a lab where everything is controlled and perfect. Nissan has done those tests.

We want to know on average what range we can expect after our cars loose capacity bars and how the heat accelerates the loss of range. We also want to know if there is an instermenation error on the car that makes us think the battery has lost more range than it has by limiting charging based on faulty measurements.

Bring on the results, enough complaining about the pack temp variations at charging which are a constant changing variable for us all each time we charge throughout the year.

 

[edatoakrun]

="EVDrive"]

...Bring on the results...

I agree. The delay in releasing the data seems to be causing irritability in some...

Are we now waiting for the results of another test, before releasing Sunday's results?

Is this additional test being run today?

 

[surfingslovak]

I agree. The delay in releasing the data seems to be causing irritability in some...

Are we now waiting for the results of another test, before releasing Sunday's results?

Is this additional test being run today?

Ed, would you it be possible to stop the armchair quarterbacking? Do you have that in you?

 

[gbarry42]

Wow, tough crowd. I'm glad Tony only has to deal with Nissan, and not you guys

 

[evnow]

Altitude doesn't "kill" range, though the effect is very significant on roads that require a lot of regen, to reduce your speed to the more efficient lower range required to rack up lots of miles. On mild ascents and descents, those that do not require regen or friction braking, the ascent energy is 100% recovered in the subsequent descent, though there is probably still a small loss of efficiency due to the more variable kW use, than on a otherwise comparable level route.

You are kidding, right ? There is never a 100% recovery - given the number of elements in between, even if each one is 95% efficient, you get to below 80% overall efficiency with regen.

 

[DaveinOlyWA]

Altitude doesn't "kill" range, though the effect is very significant on roads that require a lot of regen, to reduce your speed to the more efficient lower range required to rack up lots of miles. On mild ascents and descents, those that do not require regen or friction braking, the ascent energy is 100% recovered in the subsequent descent, though there is probably still a small loss of efficiency due to the more variable kW use, than on a otherwise comparable level route.

You are kidding, right ? There is never a 100% recovery - given the number of elements in between, even if each one is 95% efficient, you get to below 80% overall efficiency with regen.

trying to determine regen efficiency and recapture is EXTREMELY difficult but something i have been working on off and on for a while mostly with doing downhill runs to determine rate of regen and how many (if any) GIDs i regain.

just off top of my head without doing any # crunching since i have no real numbers to crunch but i would be surprised to find that we are getting anywhere near 80% back.

it might be that high, but remove losses from rolling and air friction, gravity, etc and what you get is not much

 

[GRA]

Altitude doesn't "kill" range, though the effect is very significant on roads that require a lot of regen, to reduce your speed to the more efficient lower range required to rack up lots of miles. On mild ascents and descents, those that do not require regen or friction braking, the ascent energy is 100% recovered in the subsequent descent, though there is probably still a small loss of efficiency due to the more variable kW use, than on a otherwise comparable level route.

You are kidding, right ? There is never a 100% recovery - given the number of elements in between, even if each one is 95% efficient, you get to below 80% overall efficiency with regen.

trying to determine regen efficiency and recapture is EXTREMELY difficult but something i have been working on off and on for a while mostly with doing downhill runs to determine rate of regen and how many (if any) GIDs i regain.

just off top of my head without doing any # crunching since i have no real numbers to crunch but i would be surprised to find that we are getting anywhere near 80% back.

it might be that high, but remove losses from rolling and air friction, gravity, etc and what you get is not much

I've read statements from engineers that it's 50% to 70% depending on the technology (batteries, flywheels or ultracaps), with the latter two being superior IIRC. ISTM that 100% regen would violate the 2nd law of Thermodynamics:

"The Second Law of Thermodynamics states that 'in all energy exchanges, if no energy enters or leaves the system, the potential energy of the state will always be less than that of the initial state.' This is also commonly referred to as entropy."

I'm feeling a Montgomery Scott moment coming on . . .

 

[tbleakne]

My understanding is that one preliminary observation from these tests is that the Gid readings were a little flakey near the bottom for these degraded batteries. This does not seem too surprising. Presumably the BMS has an accurate model of absolute coulombs vs voltage for a brand-new battery. The Gid calculation must use a model to compute the amount of charge between Turtle and the minimum SOC it has seen lately, since it can only count relative coulombs passing through the battery. Only a car that has discharged all the way from maximum charge to Turtle knows the real number of coulombs that were stored in the battery. It can use that along with the voltage curve to calculate the total number of Watt-hours in terms of Gids, at 80 Whr per Gid.

With degraded batteries, it is reasonable that the model of coulombs vs voltage will begin to diverge somewhat from reality. Since these cars were driven to Turtle, one would think the BMS could store a new, more accurate model, so that Gid counts would be more accurate until further battery degradation occurs.

 

[edatoakrun]

Altitude doesn't "kill" range, though the effect is very significant on roads that require a lot of regen, to reduce your speed to the more efficient lower range required to rack up lots of miles. On mild ascents and descents, those that do not require regen or friction braking, the ascent energy is 100% recovered in the subsequent descent, though there is probably still a small loss of efficiency due to the more variable kW use, than on a otherwise comparable level route.

You are kidding, right ? There is never a 100% recovery - given the number of elements in between, even if each one is 95% efficient, you get to below 80% overall efficiency with regen.

...On mild ascents and descents, those that do not require regen or friction braking, the ascent energy is 100% recovered in the subsequent descent...

I would appreciate it if someone else would make a try at explaining the two different concepts, the recovery of ascent energy in descent, and the efficiency rate of regenerative braking. I've tried, at least a half dozen times, on various threads, and for over a year now, with little success.

 

[JeremyW]

Altitude doesn't "kill" range, though the effect is very significant on roads that require a lot of regen, to reduce your speed to the more efficient lower range required to rack up lots of miles. On mild ascents and descents, those that do not require regen or friction braking, the ascent energy is 100% recovered in the subsequent descent, though there is probably still a small loss of efficiency due to the more variable kW use, than on a otherwise comparable level route.

You are kidding, right ? There is never a 100% recovery - given the number of elements in between, even if each one is 95% efficient, you get to below 80% overall efficiency with regen.

...On mild ascents and descents, those that do not require regen or friction braking, the ascent energy is 100% recovered in the subsequent descent...

I would appreciate it if someone else would make a try at explaining the two different concepts, the recovery of ascent energy in descent, and the efficiency rate of regenerative braking. I've tried, at least a half dozen times, on various threads, and for over a year now, with little success.

I think what is being described is simply coasting. The thinking that you are simply trading kinetic energy (driving up some hill) for potential energy (being at a higher altitude), and coasting on the way down to trade the potential for kinetic energy (freewheeling down the hill). In theory, you'd have 100% recovery, but since there's rolling resistance, i^2 r losses in motor windings, air resistance, the climate control you forgot you left on, etc etc... YOU WILL NEVER HAVE 100% RECOVERY EVER IN THE REAL WORLD.

Coasting is the least loss though.

 

[dgpcolorado]

...Coasting is the least loss though.

Only in situations not approaching terminal velocity. (We've had these discussions before... )

 

[sub3marathonman]

...On mild ascents and descents, those that do not require regen or friction braking, the ascent energy is 100% recovered in the subsequent descent...

I would appreciate it if someone else would make a try at explaining the two different concepts, the recovery of ascent energy in descent, and the efficiency rate of regenerative braking. I've tried, at least a half dozen times, on various threads, and for over a year now, with little success.

I think what is being described is simply coasting. The thinking that you are simply trading kinetic energy (driving up some hill) for potential energy (being at a higher altitude), and coasting on the way down to trade the potential for kinetic energy (freewheeling down the hill). In theory, you'd have 100% recovery, but since there's rolling resistance, i^2 r losses in motor windings, air resistance, the climate control you forgot you left on, etc etc... YOU WILL NEVER HAVE 100% RECOVERY EVER IN THE REAL WORLD.

Coasting is the least loss though.

JeremyW summed it up pretty good.

The only thing I'll try to add is a possible clarification to what I think edatoakrun was focused on. That would be the subsection of potential energy called gravitational potential energy. Focused ONLY on gravitational potential energy, the answer is you do "get back" 100% at the bottom of the hill. However, as is understood, you don't "get back" all the work and energy you (or the car) did to get to the top of the hill.

As a runner, I can tell you I don't want to run up and down a hill if there is a tunnel through it that's flat.

 

[LEAFer]

As a runner, I can tell you I don't want to run up and down a hill if there is a tunnel through it that's flat.

That's because a runner is like an ICE; you don't have regen . If a runner were more like an EV the choice of tunnel versus hill would less obvious. (Yes, you should still take the tunnel, but the difference in NET energy expenditure is significantly smaller in the case of the "regen runner". Unfortunately, no such thing as a human "regen runner", but the point is ... it's not a good analogy here.)