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Malm, 2011 i-MiEV, Portugal

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offgridQLD
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Post by offgridQLD »

As in the dash guage always agree with canion 100% to the instant. There was a list showing the percentage on canion corasponding to each of the 16 bars. Dig it up or I will find list it out. Follow it Acmotor. You will find your cars bars diss appear at the very second the listed % on canion vs corrosponding bar on your dash.


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Post by offgridQLD »

"I am not convinced of the % SOC that canion shows even though it gets it generally from the imiev."

This is what I'm getting at you can see the table below how every BAR relates to a exact % SOC on Canion. It never changes and is the same on every car. So Acmotor if you use canion you will see that the onset of two bars corresponds to 22% SOC on canion (the very second that it happens bars on the dash gauge and Canion SOC % are linked they are the same thing....without question! Its not an interpretation. It's the exact trigger points (a rule that never changes) try it yourself. So in your example using number of bars remaining and calling them 1kwh each is a bit rough. (yes I know you have 100's of logs to you can find patterns and iron out your +/-. Though why not use Canion that way you don't have such a big margin or error. How do you know if you have just switched to 3 bars (28% SOC) Or are just about to switch to 2 bars (23.5%) Big discrepancy between the two but on the dash (due to its 1/16 incrementation) both would show 3 bars. You only a 1 bar resolution. VS 0.5% resolution.

Even stopping at 2 bars 22% and recharging (noting the KWH from the wall ) and ignoring to add 22% to the total is ok. Just as long as each time that you recharge you are doing it from the same SOC %. This is what I was trying to do. When I do my not so regular (capacity test) and I picked 22% (the onset of two bars) as my start point that I will always use. If I had 24% SOC when I stopped I would just run the heater for a little bit to knock off the 2% So I know I am always recharging from the same %SOC back up. Pick a number it could be 25% SOC it doesn't matter.

When we are trying to determine a potential few % capacity loss having a 5% error margin by using the 16 bars isn't the best in my view. Even if you just pick a 5% block on Canion and measure whr from the wall for 5% and take note of that to see if its getting smaller.

Using bars is like trying to measure the 100m Olympic sprints using the hr hand of the clock.Image Its been simplified so people can relate to it like a old fashion fuel gauge but it just getting its data from a much more refined scale. To be honest they would have been much better of using a digital % number in the dash. It has more meaning to me than 16 bars that 1 step away from a 3 LED green, orange, red fuel gauge Image


16 BARS 100% SOC
15 BARS 92% SOC
14 BARS 85% SOC
13 BARS 80% SOC
12 BARS 75% SOC
11 BARS 70% SOC
10 BARS 65% SOC
09 BARS 60% SOC
08 BARS 55% SOC
10 BARS 65% SOC
09 BARS 60% SOC
08 BARS 55% SOC
07 BARS 50% SOC
06 BARS 45% SOC
05 BARS 40% SOC
04 BARS 34% SOC
03 BARS 28% SOC
02 BARS 22% SOC
01 BARS 17% SOC
Last edited by offgridQLD on Thu, 13 Aug 2015, 05:22, edited 1 time in total.

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Post by acmotor »

yes....
Needless to say, 100% SOC is representing less kWh as the vehicle ages.
10% SOC does not represent 1.6kWh available energy.
I was of the understanding that in turtle you cannot do 130kmph ?? or even half that.

I hate to suggest it but maybe you will need to visit vehicle full stop and see what canion says.
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Post by offgridQLD »

Yes I agree that the 100% capacity represents less and less capacity as the car get older.

like yourself. My regular rule is nothing below 20% SOC (the onset of two bars flashing is 22% SOC) So I get to a charger ASAP and typically avoid anything below 20% SOC by doing so.

I just thought it would be good to clear up that Canion and the dash gauge always agree as they are using the same simple data yet the dash display only shows it in 16 increments but I have listed the actual % of each trigger point that will never change. The amount of energy that each % represents will though and we all agree on that.

As for when the BMS pulls the pin and stops the wheels from turning or limits performance I don't know I haven't pushed my luck (others would know) All I can say is that turtle light comes on at 8.5% SOC no bars on the dash gauge. I can put my foot to the floor on our street and a good 90- 100kph with the needle berried to the right in the power section (as in the car is still pulling and would keep doing so until speed limit cut off.

The cells voltage at turtle 8.5% is over 3.6v on all cells at rest. So yes sure the car must be hiding some capacity below the turtle ...being conservative. Yes I to don't consider that capacity that I would use.
Image

Though there is a overriding rule that if a cell reaches 2.75v the BMS will pull the pin no matter what the SOC on the capacity gauge is.

I'm not going to take my car down to 0% SOC just to come up with a number I'm happy to use the 22% (two bars) as my lowest SOC and measure what the BMS is letting me consume (Or what it is calling 78% of my capacity) I can put a KWH number to it and watch it change. Though I am having trouble with consistency of that number as mentioned but perhaps that's down to temp variations when testing (SEQ this time of year is all aver the place one day 28C) the next evening 10C. So I will pay more attention to battery temps.

Acmotor, I guess if you made sure you started your metering at the (onset) of a particular bar vanishing then you could have a stable datum to start from each time.Otherwise you just have to be content with a 5% error margin vs a 0.5%.
Last edited by offgridQLD on Thu, 13 Aug 2015, 08:41, edited 1 time in total.

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Post by offgridQLD »

Just for comparison this is last time I took it to turtle (8.5% SOC) one year ago.Looks like cell 56 is the strongest cell both times. But we are talking 20mv variation at that low SOC. I'm very impressed with the LEV50 Cells and how they are managed in the car Image I might continue to do this test every year.

Image
Last edited by offgridQLD on Thu, 13 Aug 2015, 08:27, edited 1 time in total.

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Post by offgridQLD »

Yes forget about 16kwh number that keeps getting thrown around might be ok for marketing of the car but doesn't relate much when the car is in use.

Personally for me it's all about voltage. The car stops charging when the cells are at 4.105V and it turns off at 2.75V (on any cell) hard and fast rule. 4.105v is always 100% SOC. How much capacity you have between the two voltage points is your max usable capacity.

How much capacity the BMU wants to call 100% to 22% incrementation and self calibrates it's self for is up to the BMU. If it want's to call 100% to 22% just 5kwh then so be it not much you can do about it.
Last edited by offgridQLD on Thu, 13 Aug 2015, 08:42, edited 1 time in total.

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Post by acmotor »

Yep, that's what I was saying about the voltage limits.

Do the test printscreen at 100k/h and power meter pegged i.e. cells under load. I think it is a better measure of cell health.
e.g. one I took a while back at 1 bar

Image

edit: GPS wasn't on at the time

I still understand that turtle won't let you access full power, but I can't speak from experience as I have never been there.
Next time you go there grab a screen under load.
Last edited by acmotor on Thu, 13 Aug 2015, 08:58, edited 1 time in total.
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Post by offgridQLD »

Nice screen shot. You were doing 101kph at the time by the dash speedo up the top. I like that under load test. Your pack looked healthy. I will do the same next time I am at 16% SOC.

Ask Malm for a screen shot He seems to linger in the shallows often Image

I was thinking the same thing Acmotor. That some kind of dramatic limitation on performance the second turtle was activated. Like a limp mode. Though I didn't find that. Perhaps there is some kind of lower SOC where this is activated (perhaps its voltage dependent. Though I haven't noticed any crawl mode at turtle onset. Though I didn't spend very long there as I was driving around the block.

PS, Did you hear the news that some one in WA just purchased a new complete pack for just $5700. What do you make of this?
Last edited by offgridQLD on Thu, 13 Aug 2015, 09:07, edited 1 time in total.

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Post by reecho »

Soon as any of the cells hit 2.75V power drops immediately. You can get a bunny hop effect.... Image

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Post by acmotor »

Yes, following skylogger posts on battery swap.
If I could pay $6,000 for the originally advertised 160km range I would jump at it.
The reality is I am still happy with my present 100km range though.

I guess the exercise of the 2010 pack says that battery care is important.
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Post by Malm »

Interesting that turtle appears at different SoC in different i-MiEV. In mine, turtle appears at 9,5% SoC. But I have the information that in other i-MiEV it appears at 10%.

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Post by Malm »

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Post by Malm »

0,0% and no turtle anymore. The car will stop no matter what voltage you are.

https://www.youtube.com/watch?v=PkWW5w2e4XU
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Post by offgridQLD »

Yes I agree Malm. All other % SOC increments from 100% down are the same on every Imiev. Though like you say the Turtle doesn't follow this rule.

What I'm starting to think is that the Energy meter or (usable capacity settings) in the Imiev is something I want to know more about. I don't feel this restriction is always correct and perhaps in some cases its restricting the usable capacity to much.

I base this on how strong- high the cell voltage is even when you are at turtle.

The only real way to know is to cycle the weakest cell in your pack and measure the whr/AH capacity at the cell level. The good thing is we have some one in AU who recently replaced his pack with a new one and has access to his old cells now. So he can perform this cell level capacity test and we will know the answer then Image

Then we can stop messing around with Bars, Turtles and flashing dash gauges and start playing with some real usable data.

Kurt.


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Post by acmotor »

yes, more info required.
There is pack voltage, cell voltage and energy totally in pack and energy available limit due to an individual cell voltage.
A 'discharged' pack may still have several kWh left in the stronger cells but no accessible due to the low voltage on the weakest cell.
The energy meter and canion would read zero when the weakest cell reaches lower voltage limit.... or do they report the other energy still in pack ?
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Post by offgridQLD »

"The energy meter and canion would read zero when the weakest cell reaches lower voltage limit.... or do they report the other energy still in pack ? "

I think it's a bit different to that as they dont line up (as in 0% SOC dosn't = a cell at 2.75). The energy meter/Canion will go all the way down to 0% SOC and then car will stop moving. As in the BMS pulls the pin on everything. The only other time that will happen is if any cell hits 2.75v on the way. no matter what the SOC is on meters.

I have never hit 2.75V (BMS LVD) and even at 8.5% SOC my pack individual cell voltage is so high and balance differential is only 20mv variation). That I'm almost sure I would hit 0% SOC and be a long way off of hitting 2.75v on any cell. So it would be the 0% SOC on the dash gauge/Canion that would activate the BMS disconnect based on 0%SOC and end the fun(not LVD on a cell).

So we all agree the whr capacity from 0% SOC - 100% SOC gets smaller and smaller as the car ages. Though what we don't know enough about (or how good a job it's doing) Is the logic behind how the Imiev reconfigures a new 0-100% capacity. How often, how much and based on what?

It can't be redetermined by going 2.75v and recharging to 100% (as most of us have never hit that low voltage befor, myself included. There is some predetermined logic for the life of the car that determines the new capacity. As mentioned it can be reset using the factory programing tool. As a newly installed pack was restricted to the old packs limited capacity until it was reset.


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Post by offgridQLD »

I also wonder if the old pack was put back into the car without resetting the capacity calibration. Would the old pack have more usable scope. Or would it hit LDV(2.75v) with 40% SOC on the dash gauge. Apparently the replaced old pack still had good balance so a week cell starts to not look likely.

Oh the fun I could have with two packs Image

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Post by Malm »

It will stop with 40% SoC and one cell at 2,75 V. No doubt about that. Two years ago my car stopped at 14,5% SoC, and I'm not the only one who reported this behavior. But after some time it did a recalculation of its capacity, and after that, with less energy in every bar, it goes to 0,0% SoC.
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Post by offgridQLD »

"Two years ago my car stopped at 14,5% SoC"

Well there is proof that the BMS gets it wrong. Though did it stop at 14.5% SOC because you hit 2.75v on one cell?

I assume the BMS can get it wrong in the other direction to. Car stops at 0% SOC and all cells in balance + a good reserve to go.

I have the feeling the car in question (one with pack replaced) has a BMS that thinks the battery capacity is less than it really is. Time will tell when it's cycle tested on the bench.

If not then the pack must have been abused a lot some how.



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Post by Malm »

yes, 2,75 V in the weakest cell.

The car in question was used in a hot climate. If the car is for many days constantly at 40 ºC to 50 ºC, then I will expect to see the capacity going down very fast.
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Post by Malm »

I believe, 4 years and 4 months ago, my i-MiEV had 48 Ah. I bought it new in April 2011. At that time I was not aware about the effect of 40 ºC in my battery, so, in the summers of 2012 and 2013 I made several long journeys with it, day by day (I was spending more time in the car then doing anything else).

In march 2014, the result was 36,4 Ah. In three years I lost 11,6 Ah, that is less 24,2% of the original capacity.

I said to myself, no, I will not be here with crossed arms looking to this disappearing capacity, so I made to changes: 1 - i-MiEV always stays at night outside, because temperatures at night will be lower then inside and 2 - When temperatures are above 25 ºC the cold air from de AC will be going to the pack.

In Juliet 2015 I finally went to the fourth annual check. And the result was an astonishing 35 Ah. In one month, three months and fifteen days, I only lost 1,4 Ah (1,08 Ah/year).

So, in the first three years I lost 3,8 Ah/year

In the last 15 months I lost 1,08 Ah/year

No one, four years ago could show me this. That's a big lesson that I took myself. I think no other I-MiEV in all world is showing how big is the influence of heat in the longevity of the battery. Take it or not, that's yours choice.



Last edited by Malm on Wed, 19 Aug 2015, 04:35, edited 1 time in total.
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Post by offgridQLD »

Yes it is a known fact that elevated temperature over the life of the battery will have a negative impact on its life.

I do my best to avid it. Car is always parked in a cool garage under my house (one is a air conditioned garage over summer) I have flexibility when I use my car to So I can choose to not go out in the middle of a hot day or park it out in the heat for long periods on hot days.

While I totally agree with your thinking on battery temperature. I do also wonder if some element of your results are to do with the non linear degrading of the battery. For example it could degrade the first 20% in 3 years then take a further 6 years to degrade the next 20% (just an example).

Yesterday I did a very balanced mixed drive (A even mix of city 60kph, outer city 80kph and freeway 100kph and a good mix of hills and flat section. It was spot on 100km distance (50km each way) On the way back I had AC on. I had my range extender with me (25kg of battery and 15kg of inverter) Just incase I wanted to extend the trip.


I returned with 5 bars (some where around 36-38% SOC on my energy meter. I always consider from new My Imiev has a safe 100km range. Though reality it's a very conservative safe range.

Kurt



Last edited by offgridQLD on Wed, 19 Aug 2015, 05:08, edited 1 time in total.

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Post by Malm »

I see your point and I also agree degradation will go faster in the first year, no matter what. But for me with temperatures of 40 ºC day by day without letting it going colder, will make degradation go fast even in a battery who lost already 40%. So, at the end of the first year, its all about temperature, nothing else meters.
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Post by Malm »

Ok, not only temperature, time is also important. Maybe only time, and high temperatures just speed the clock.
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Post by offgridQLD »

Time at a high temp. The weighted average temp of the battery. Spending 2hrs at elevated temps (say 40C) is much less impact than a average temp over the life of the car. 25c vs 20c over its life.

I also think to get best value from the battery you need to use it.

I was thinking of what might be the value proposition of the Imiev in comparison to small efficient petrol car. Using a best case scenario. Some one who has a 80km trip every day 7 days a week ( 560km a week 30,000km PA) would drive 150,000km over 5 year (and lets just say that's how long the battery last). In Au the battery is $5,700 for a new one. That's 30,000km for $1,140 . $3.80 pr 100km driven. Not that good (even if your recharge power is free) As $3.80 could purchase about 3lt of fuel and the Imiev uses about $2 in offpeak electricity to recharge after 100km driving (for people on the grid) so $5.80 pr 100km about the equivalent of 4.4lt / 100km in petrol costs.

For the table to turn more you would need more life in years from the battery.

Still for me cost isn't everything even if its the same price as having a very efficient petrol car I prefer electric car for many other reasons.

kurt
Last edited by offgridQLD on Wed, 19 Aug 2015, 05:43, edited 1 time in total.

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