Battery Ageing Model

[AndY1]

Why is Soul EV averaged (blue X) so much lower than the My Soul EV (pink X) values? Shouldn't it be somewhere in between?

 

[JejuSoul]

Why is Soul EV averaged (blue X) so much lower than the My Soul EV (pink X) values? Shouldn't it be somewhere in between?

The Soul EV averaged data is from ten different cars. The 'My Soul EV' data is all from my car. My car has slightly less deterioration than the average of the ten. Graphing the two different types of data is not meant to show exact results, because: 1) none of the Soul EVs of the ten reporting deterioration data on this forum are from Phoenix, 2) the AVT battery deterioration is laboratory measured - ours is not, 3) the AVT fleet data comes from cars that are driven the same way on the same roads.

What this graph might show is that the deterioration of the battery in hot climates might not be much worse than elsewhere if the battery has good thermal management. We don't know yet if the Soul EV battery has good thermal management in regards to deterioration. Will be interesting to see the future AVT laboratory data.

 

[AndY1]

Why do you think you Soul's battery is deteriorating more slowly than of the other ten? Is it the ambient temperature? Depth of discharge?

My Ampera's battery is submerged in Dexcool and is liquid cooled with the car's AC unit and liquid heated with a 1.8kW heater. If it reaches 30°C, it cools the battery down to 24°C - when parked (connected to the grid or not) and when the car is on.
If the battery temperature goes below 8°C, the 1.8kW heater heats it up to 14°C, but it starts heating only when the car is turned on or when it's connected to the grid.

 

[JejuSoul]

Why do you think you Soul's battery is deteriorating more slowly than of the other ten?

There is no statistical significance in the small differences currently measured. (Except for 1 car in Switzerland that had high deterioration quite quickly). As yet we have nothing to show that climate, driving style, type of ch arger makes any difference to deterioration. All we can see is that if these deterioration rates are real and if they continued in a straight line for 6 years most cars would need a battery replacement. But the line probably won't be linear!
Here's the latest data for the 10 cars.

 

[ZuinigeRijder]

In the Soul Spy topic a spreadsheet is given, showing different values you can get from OBDII.

But there are 2 different values:

• State of Charge of Battery(BMS)
  SOC Display

There are not the same on my Kia Soul EV (and also not by others).

A measurement a few days ago, without fully charged showed (2% difference):

• State of Charge of Battery(BMS) 55 %
  SOC Display 57 %

Today, when charged for 100% there was a difference of 5%:

• State of Charge of Battery(BMS) 95 %
  SOC Display 100 %

And when driving home, the difference between those were becoming smaller.

My theory is that you can compute the State of Health (SOH) with those 2 values.
The BMS SOC is related to the full capacity of the battery (30.5 kWh).
The Display SOC is related to the capacity for driving (27 kWh).

So it means that I have already lost 5% of the total capacity. But probably the SOH is meant regarding the driving capacity.
In this case:

State of Charge of Battery(BMS)	95	%	remaining	29.0	kWh	SOH	107	%
SOC Display	100	%	remaining	27.0	kWh

As long as the remaining driving capacity is above 27 kWh, the SOH will be above 100% and SOC Display will be 100%.

Also the Max Deterioration and Min Deterioration of the batteries is available for the OBDII.
For me these are 11.6% and 10%, with the formula's in the spreadsheet. But I think those values need to be divided by 2, so approx 5%.

 

[2soul]

I've noticed the same difference in SOC Battery and SOC Display values, fluctuating between 2-4% - difference smaller as you drive.

If your theory is correct, I've lost about 4% capacity - which sounds reasonably realistic given the mileage (19000km/12000miles) and if we are going to compare with other EVs. 4% is approx. 1,2kWh of the total capacity, which means the total remaining battery capacity is 29,2kWh. The remaining buffer would then be approx. 2,2kWh. It would be interesting to know how much buffer capacity the BMS holds before we experience a real drop in range.

 

[JejuSoul]

My theory is that you can compute the State of Health (SOH) with those 2 values.
The BMS SOC is related to the full capacity of the battery (30.5 kWh).
The Display SOC is related to the capacity for driving (27 kWh).

I don't think it will be that easy. The SOC (display) starts higher than the SOC(BMS) but once you get down to a low SOC it reverses. There is always a buffer of unused capacity. So if you were right SOC(BMS) should always be lower.
I want to see more data taken by a variety of cars at 100% SOC to see how useful this really is.
I very rarely charge up to 100% so have no data yet for my car. Will post when I do.

It would be interesting to know how much buffer capacity the BMS holds before we experience a real drop in range.

I agree. Given that it is winter none of us would be able to record any loss of range for at least a few more months. But I doubt any of the cars with currently measured OBD data have lost range, or if they have it would be too small to measure. The first car to show a loss in range would probably be iletric's who has done over 42,000km.

...I am curious to see what the 2nd summer of this car will be like. I expect starting range at at least 88. It was 90-91 last fall (before the cold).

2soul can you post some data about your car. Location, age, km, max det, min det, Cum Energy Charged and Discharged. I would like to add your car as a data point in the battery deterioration graph.

 

[Tom]

I drove downhill a month ago and I recuperated arround another 1.5kWh still as the SOC (display) was showing me a 100% SOC.
I started with 95% SOC and rec was 3.2kWh within a distance of 12.7km.

Usually I can drive downhill at home from 700 to 500 meter above seelevel within 10km wit no problems and fully rec even if the SOC is 100% BUT there it was to steep and
after arround 10km my rec was not longer in action and I had to use my regulary breaks downhill........what a energy waste .....and I was charging the car to 95% the night befor.

 

[JejuSoul]

About the two values for SOC.
One possible interpretation is that the Soul Ev is similar to the N issan L eaf.
From the Post Your Battery Degradation Results thread here http://mynissanleaf.com/viewtopic.php?f=31&t=13371&start=510

There is more than one SOC%.
There is an internal SOC% used by the computer systems inside the L eaf and you can get that number from l eafspy.
The other is the dash SOC% and it shows true in the middle but fudges on a curve at the top and bottom of the pack.
100% from l eafspy is not the same as 100% from dash.

Another possibility is that SOC(BMS) shows the SOC for the current total battery pack capacity.
There is always a buffer at the top and bottom of the pack that cannot be used.
SOC(display) shows the SOC for current usable battery pack capacity.
Hence if SOC(BMS) shows 95% when SOC(display) shows 100% it means that the buffer at the top is 5% of the the current total battery pack capacity.
Similarly if SOC(BMS) shows 5% when SOC(display) shows 0% it means that the buffer at the bottom is 5% of the the current total battery pack capacity.
We don't know the current total battery pack capacity from this, and don't know the degradation.
But if as Tom pointed out above we could measure how many kWh you can add to the pack after 100% charging has finished perhaps we could get these values.

An extra point to this. Lots of people complain that they can never recreate the original high mileage on the GOM that comes when the car is brand new.
Perhaps this is because the new battery is fully charged. It is built that way - nothing sneaky on Kia's part. A brand new battery has 30.5kWh.
But users will only be able to charge it up to 100% of usable capacity which is 27kWh.

 

[ZuinigeRijder]

Also the Max Deterioration and Min Deterioration of the batteries is available for the OBDII.
For me these are 11.6% and 10%, with the formula's in the spreadsheet. But I think those values need to be divided by 2, so approx 5%.

Interesting enough, the battery degradation has been diminished according to the read-outs:
Max Deterioration from 11.6% to 11.1%
Min Deterioration from 10% to 9.6%

Did someone else see this happen?
Note that here in the Netherlands the cold weather was changed in one day from 0 degrees Celcius to +13 degrees Celcius.
Also the BMS does not cope well with this, because the predicted range is now way off (too low) the actual range.

 

[JejuSoul]

Interesting enough, the battery degradation has been diminished according to the read-outs
Did someone else see this happen?

Yes. It is common. See the battery calibration thread. My car had quite low deterioration for a long while then made a sudden large jump down. After that it rebounded upwards for a few weeks before stabilizing. I think the readouts often have a substantial error. This gets corrected every so often.

...the cold weather was changed in one day from 0 degrees Celcius to +13 degrees Celcius. ...

Here the cold weather changed in two days from -6 degrees Celsius to +11 degrees Celsius. There has been a very fast melt. My house had about 30 cm of snow. The mountain behind about 1m 30cm.
The GOM on my car has rebounded fairly quickly. Back at 155km from 108km. But I did not drive in the snow.

 

[Tom]

I drove downhill a month ago and I recuperated arround another 1.5kWh still as the SOC (display) was showing me a 100% SOC.
I started with 95% SOC and rec was 3.2kWh within a distance of 12.7km.

Usually I can drive downhill at home from 700 to 500 meter above seelevel within 10km wit no problems and fully rec even if the SOC is 100% BUT there it was to steep and
after arround 10km my rec was not longer in action and I had to use my regulary breaks downhill........what a energy waste .....and I was charging the car to 95% the night befor.

I wrote here something wrong at all.

So I try it again with the right values:
I drove downhill a month ago and I recuperated 3.2kWh within a distance of 12.7km..
I started with 95% SOC.
At some point I had the 100% SOC and as the Soul usually does, it still recuperated.
After this distance of 12.7km I had the follwing values with the OVMS command trip:
Dis: -2.2kWh
Rec: 3.2kWh
Sum: 1.0kWh

So the batterie was charged with 2.2kWh with a start SOC of 95%.

By the way: The batterie temperature (and the car) was arround freezing point at the moment we started with 95% SOC.

 

[ZuinigeRijder]

On this forum the SOH is measured as being 96.2 % after driving 34000 km and also using CHADEMO regularly.

Unfortunately no information about the minimum and maximum battery degradation numbers which can be measured by OBDII dongle.

 

[JejuSoul]

ZuinigeRijder: thanks for posting that. I will post about how we find the SOH on the Soul Spy thread. In terms of battery ageing this data seems reasonable and fits with what we are seeing. That 96.2 % after driving 34,000 km will be measuring usable capacity not total as we have been doing until now. This car is in Switzerland. It's pretty much the same as the deterioration in range posted by mtndrew1 from Southern California - "I've only lost 5.56% of usable capacity in ~21,000 miles"

 

[JejuSoul]

Nothing new in the data we are collecting. We have no measurable difference in the deterioration from any climate, driving style or type of ch arger. In fact by some statistical fluke the current trend lines for my car in South Korea, Elmil's car in Sweden and an average of 14 cars around the world are all identical.
In the graphic below my car is blue, Elmil's pink. The cars are the same age, but his has driven twice as far. The values on my car are static for a while and then yo-yo around. His seem a bit more stable. Neither seem very linear though, so fitting a linear trendline should be taken with a very large grain of salt. Also note that all of these cars still had 100% SOH. We don't know yet how this scale will match actual deterioration in range.

 

[Elmil]

As it happens, I had another decrease of my deterioration values last night.

Date        Km        Max   Cell    Min    Cell   SOC
2015-11-01           9.3%   32     8.3%    1   92.5%
2015-11-05  18780    9.8%    2     8.4%    8   92.5%
2015-11-19  19751   10.3%   24     9.2%    1   91.5%
2015-12-23  22610   11.2%    3    10.2%    8   92.0%
2016-02-29  27339    9.8%    2     8,8%    8   92.0%
2016-04-04  30209    7.9%   37     6.5%   20   92.5%

Since friday morning and during the weekend I drove a total of 180km from full charge down to 5% displayed. When parked at home I left the car running until flashing turtle at 3%. Charged overnight (230V/2kW), and the deterioration values changed at the very same charge level as the previous times, i.e. when all 96 cells were at 0xCC (4.08V).

The used energy during driving, and the charged energy:

Discharged (97% of usable): 25.1kWh   72.0Ah
Charged (97% of usable):    26.1kWh   72.0Ah

It seems my battery has lost a little bit of capacity, but not as much as you could expect after 30000km.
Having 30000km service next week, will be back with updated SOH value then.

 

[Birkeland]

Then I have finally gotten an OBDII bluetooth adapter to work with Torque Pro.

My data:
km: 19.094
Max deterioration: 7,2%
Min deterioration: 4,9%
Car age: 12 months
Location: Norway
Cumulative Energy Charged: 3.990kWh
Cumulative Energy Discharged: 3.889kWh

It has been over a month since I charged the car to 100% (I usually leave it at 40% and charge the car to 60-70% with my 6.6kW charger just before I need it). I will recharge my car to 100% soon to see if the balancing of the battery cells will change the numbers.

 

[JejuSoul]

Birkeland: good to see those deterioration numbers. Your car seems to be below average. Perhaps Scandinavia will gain a lead here given Elmil's improved numbers in the post above. To calibrate your battery pack you need to charge to 100% then drive the pack down to nearly empty and then charge to 100% again. It is on this 2nd 100% charge that calibration occurs. I have had my car for nearly a year and have never gone below 13% yet. I began a calibration test today and will complete it tomorrow. Results can be either up or down. We just all hope to be lucky like Elmil.

Results for my calibration test:- charged to 100%, drove 200km, charged to 100%
I stopped driving and started charging at 9% SOC.
GOM before 174km, GOM after 178km. My highest so far this Spring.
Deterioration values did reset. min det reduced from 6.8% to 5.5% at just above 4.08V (some cells were showing 4.10V) It was at 92% SOC, Battery pack =393V
max det reduced from 9.0% to 8.5% at 100% after I turned the car off to unplug the charger.
I have seen much greater movement in these numbers recently that was not associated with charging to 100%.

Energy charged = 25.0 kWh for 91% (based on the BMS data) => Full pack 25/0.91 = 27.47kWh
Energy discharged = 23.9 kWh for 91% (based on the BMS data) => Full pack 23.9/0.91 = 26.3kWh

The energy charged figure is simple; it is the difference in cumulative energy charged before and after charging.
The energy discharged is the difference in cumulative energy discharged during driving minus the regenerative energy put back into the battery.

In my case the 200km driven included a significant mountain stretch. (up 1100m). The regenerated energy was 11.3kWh

 

[Birkeland]

I charged from 27% to 100% during the night to prepare for the calibration by driving the battery almost empty and charge it back up again. But when I woke up this morning, the values had allready changed:

Before charge:
Min deterioration: 4,9%
Max deterioration: 7,2%

After 100% charge:
Min deterioration: 3,7%
Max deterioration: 5,4%

JejuSoul: Will the battery calibrate further by me running the battery almost empty and chargeing it back up again as you described?

 

[JejuSoul]

Birkeland: the only way to know if the numbers will change again is to try it and see. Your numbers are already the best for any car we have tested so far. Don't be surprised by any change up, down, or not at all. I am not sure these numbers are that important taken as a single reading. Averaged over 6 months maybe. My car has jumped around by as much as 6% recently.

The other useful thing to do when driving down from 100% to zero is to monitor the Cumulative Energy Charged and Discharged counters. Even though my Deterioration numbers are worse than Elmil's currently I am able to get more energy into and out of a full charge. He has driven twice as far so that makes sense. He probably has some actual deterioration at 30,000 km. At 15,000km I probably don't. It will be interesting to see your figures.