Comparing BMS data on the Soul EV with the Ray EV

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I am currently driving a 2012 Kia Ray EV with about 56,000km on the odometer.
Here are some photos taken on a recent range test.
I am using the same torque codes to read the BMS as we use on the Soul EV.

I charged to 100%, drove 100km until the battery was below 10% and then recharged to 100%.
The Ray EV does not display SOC, nor is there a reading in the BMS for SOC (display).
At 100% charge SOC (BMS) displayed 90%. At the end SOC (BMS) displayed 9.5%.







At each of these points I took a screenshot of the BMS data.







Energy charged = 14 kWh for 90% (roughly) => Full pack 24.5/0.9 = 15.5kWh
Energy discharged = 14 kWh for 90% (roughly) => Full pack 14/0.9 = 15.5kWh
Regenerated Energy on the trip was 5kWh.

Ah charged = 40 Ah for 90% (roughly) => Full pack 40/0.9 = 44.4Ah
Ah discharged = 41 Ah for 90% (roughly) => Full pack 41/0.9 = 45.5Ah
Regenerated Ah on the trip was 16Ah.

These numbers at first seemed reasonable but then I checked with this.



From the external stand in 4 hours of charging I loaded 13.7kWh. There is no way I could have got 14kWh into the battery.
I was loading 16A at just under 220V. The input power was just under 3.5kW. The external c harger is correct.

The energy draw on the battery was between 2.6kW and 3.0kW depending whether the EWP was on or not. Assuming an average of 2.8kW the efficiency of the process is about 80%. I was watching this data on the screen, but didn't take a screen shot. I have the logs so will be able to get a more accurate value. Using this value suggests that in 4 hours I got 11.2kWh and thus the usable pack capacity is 12.4kWh

Update - from the logfile actual average energy draw was -2.83kW, so in 4 hours I would have charged 11.32kWh. Efficiency = 82.7%.
This reading would give a max battery capacity of about 12.6kWh.
Seems a more reasonable number given my Soul EV with 27kWh would drive 200k on a similar trip.

The main lesson here is that the Cumulative Energy Counters reported by the BMS are not to be trusted.

Have you a Chademo plug on this car ?
Chademo kWh-meter (in DC) can be more accurate than type 1 charger (in AC) ... no ?

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Yes the Ray EV has a Chademo inlet. I will test that later.
Here is a graph from the charging session yesterday.



Am curious why does SOC (BMS) not increase in a straight line. why the change between 38% and 44% where it goes up faster?
Does the Soul EV show this behaviour too?

SOC BMS is always a formula between the max voltage (at the cell ! so 4,15v for example ... or less depending of the others cells) and balancing stage (cell deviation) with a correction of Ah-meter.

so ... battery is old or car have been storage for months before you run and charge.

That's why, in industrial usage ... we use LifePO4 for long period and not Li-Ion/Li-NMC.

JejuSoul said:

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Am curious why does SOC (BMS) not increase in a straight line. why the change between 38% and 44% where it goes up faster?
Does the Soul EV show this behaviour too?

Click to expand...

I saw a similar increase on the loaner Soul EV I used a year ago. That car was the dealers demo and had probably always been c harged to 84% at their 20 kW Chademo. Had all zeros on deterioration values and around 1000 km on the odometer as I recall.
When I used a Chademo FC on the road to work, the last SOC% between 81 to 84% went really quick, so I guess some adaption to new situation occured.

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Yes. I assume the BMS will adjust the SOC during charging if it figures out it is badly calibrated.
Here is what happens on my Soul EV.

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Done another range test on my Ray EV. This time drove 91km over 3 days and got down to 4.5% SOC (BMS). It shows turtle!
Does anyone know for sure what SOC (BMS) shows when the pack is empty with the Soul EV. I have never been below 10%.



The stats based on the Cumulative Energy Counters are -

Energy charged = 14.6 kWh for 95% (roughly) => Full pack 14.6/0.95 = 15.4 kWh
Energy discharged = 9 kWh for 95% (roughly) => Full pack 9/0.95 = 9.4 kWh
Regenerated Energy on the trip was 4 kWh.

Ah charged = 42 Ah for 95% (roughly) => Full pack 42/0.95 = 44.0 Ah
Ah discharged = 42 Ah for 95% (roughly) => Full pack 42/0.95 = 44.0 Ah
Regenerated Ah on the trip was 12 Ah. (This time there was no mountain driving.)

The Ah numbers are consistent with the test done two weeks ago.
I am struggling to make sense of the kWh figures. I don't know what such a huge discrepancy means.

Update - from the logfile actual average energy draw was -2.742kW, so in 4 hours and 8 minutes I would have charged 11.33 kWh.
This reading would give a max battery capacity of about 11.9 kWh.
It is very similar to the previous value. It seems the actual energy capacity now in the pack is about 12 kWh

kWh are based on the voltage measure.
When you charge the pack and it is old, the voltage is always high than rise.
At contrary, when you discharge the pack, the voltage SAG really HUGE when you use to drive.

at cell level, it's like that :
- cell can evolve from 3,00v to 4,20v
- builder allow only 3,20v and 4,15v
- when you charge and the pack is old, the voltage evolve from 3,90v to 4,10v (and BMS strategic change to balance the cell from 4,00v to 4,15v for example)
- when you discharge, the cell voltage evolve (when it is old) from 3,85v to 3,30v (4,15v~4,10v is a hollow point)

and then, the kWh is different than the Ah.
on Bike, we only measure the Ah because is more like the fuel liter in a tank.

kWh is good to see ageing effect on a pack.
Usually, on bike, the cells are deviate before the SAG voltage of the pack.

On this Kia Ray EV, it's a good product so all cells aging together.

What is your cell deviation at drive and at 7kW charger and at Chademo 43kW charger ?
It's a good indicator, too ... especially when the pack are below 10%.

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Just like in my previous test SOC (BMS) did not increase in a straight line. Why the change between 38% and 44% where it goes up faster?
This time I do not believe it is badly calibrated, given that I have already done a calibration test a week before.



Also the Cumulative Energy counter shows the same anomaly. This explains why the Energy Counter cannot be used to measure the capacity of the battery



The Cumulative Current is the same.



To show this is not real. The Energy Draw does not show this effect.

JejuSoul said:

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Done another range test on my Ray EV. This time drove 91km over 3 days and got down to 4.5% SOC (BMS). It shows turtle!
Does anyone know for sure what SOC (BMS) shows when the pack is empty with the Soul EV. I have never been below 10%.

Click to expand...

Yes, when I did a 100% to 0% range check last summer, the battery turned off at 297.2V while the SOC (displ) went from 1.0% to 0.0%.
The SOC (BMS) showed 2.5% and went to 2.0% a couple of seconds later and stayed so for two minutes until I connected the charg er.

Elmil said:

Yes, when I did a 100% to 0% range check last summer, the battery turned off at 297.2V while the SOC (displ) went from 1.0% to 0.0%. The SOC (BMS) showed 2.5% and went to 2.0% a couple of seconds later and stayed so for two minutes until I connected the charg er.

Click to expand...

Thanks Elmil, that's useful data for comparison. From August 5th last year on the Battery Ageing thread.

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For the Soul EV we have the AVTA site laboratory data. - https://avt.inl.gov/vehicle-button/2015-kia-soul

From the Vehicle Specifications and Testing Results we can see that -
Nominal Voltage = 360V
Number of Cells = 96
Nominal Cell Voltage = 360 / 96 = 3.75V

Total Energy Capacity in kWh = Nominal Voltage * Total Capacity Ah = 360 * 85 = 30.6 kWh
Usable Energy Capacity in kWh = Nominal Voltage * Usable Capacity Ah= 360 * 75 / 1000 = 27 kWh

From the Battery Pack Laboratory Testing Results we can see that as the pack approaches empty (the last 10%), the available energy left in the pack drops quickly.



The picture above is a lab test of the full pack. Presumably bypassing the BMS which only allows access to the usable portion of the pack.
The full pack has a voltage range from 225V to 415V. Cell Voltages from 2.3V to 4.3V
The usable pack has a voltage range from 297V to 398V. Cell Voltages from 3..09V to 4.14V

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Here is a graph of the capacity charged against battery voltage for my Ray EV. Notice how voltage rises quickly in the bottom 10% of the pack.



I have never driven my Soul EV below 10% SOC so I have never seen this on my Soul EV. But using the data above given by Elmil and Leefer I assume the effect is the same.

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Here is the graph from charging my Soul EV 0-100% (2-95% BMS) last summer. The voltage rise is pretty much the same, as expected.

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Thanks Elmil, knowing how the Soul EV behaves at the very top and bottom of the battery pack when SOH is 100% is probably going to be useful for comparing the changes that occur as the battery degrades.

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Here's the Ray EV chademo charging from 17% to 80% .Took 16 minutes. Ambient temp = 24C






The Average Energy Draw = -32kW. Time = 974 secs. I added 32 * 974 / 3600 = 8.57 kWh ( => estimate of total pack size 11.97 kWh)
CEC final - CEC start = 11877.4 - 11866.0 = 11.4 kWh ( => estimate of total pack size 15.93 kWh)

I estimate pack size by dividing first by .63 because 63% was added. And then multiplying by .88 because SOC BMS on the Ray EV has a range 2.0 % to 90%.

So like the two L2 charges when I calculate using the energy draw I get a pack size of about 12 kWh. But using the Cumulative Energy Counter I get a pack size nearly 15.5 kWh.

Am writing about the temperature increase during Chademo here TMS Behavior

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Here's another Ray EV chademo session - charging from 10.5% to 80% .Took 18 minutes. Ambient temp = 20C



I will also discuss this charging session at - Somes graphics about Chademo Charge Station.

The Average Energy Draw = -34.4kW. Time = 977 secs. I calculated 34.4 * 977 / 3600 = 9.33 kWh ( => estimate of total pack size 11.8 kWh)

CEC final - CEC start = 11895.0 - 11882.5 = 12.5 kWh ( => estimate of total pack size 15.83 kWh)

I estimate pack size by dividing first by .695 because 69.5% was added. And then multiplying by .88 because SOC BMS on the Ray EV has a range 2.0 % to 90%.

As before when I calculate using the energy draw I get a pack size of about 12 kWh. But using the Cumulative Energy Counter I get a pack size nearly 15.5 kWh. The energy counters are clearly wrong. Seen from the display on the Chademo stand. Total energy going through the external stand is 10.41 kWh. This doesn't include the efficiency loss going into the battery.



Adding 9.33 kWh implies an efficiency of 89.6%.
Adding 12.5 kWh is impossible.

My current thinking is that my actual energy capacity is around 12 kWh but the Energy Counters are still working as if there had been no degradation.
They are just assuming that 1 complete battery cycle is the original usable battery capacity. Anyone got any better ideas.

Update:
Originally I used his equation - it includes the time cells were balancing but no energy was going in.
I changed it to remove the time balancing.
Either way pack size ends up to be about 12 kWh.
The Average Energy Draw = -33.8kW. Time = 1060 secs. I calculated 33.8 * 1060 / 3600 = 9.95 kWh ( => estimate of total pack size 12.6 kWh)

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Here's my car L2 charging from last week. My odometer is 56,000km.
Why the change between 38% and 44% where it goes up faster?



And here is a different Ray EV; odometer is 28,000km.
A 16A L2 charge manually stopped at 65%.
The same change in slope between 38% and 44% where it goes up faster.



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The Soul EV does not have this correction in SOC mid slope during charging. But it seems a similar behaviour is also seem in the Nissan L eaf.



From - What is a "Gid"?

A possible explanation was -

Ingineer said:

The Battery ECU computes SOC and Watt-hours remaining by 2 methods; One is by coulomb counting with a hall-effect ammeter, and the other is by watching open-circuit voltage of the pack and performing a complex calculation based on multiple inputs. Because the coulomb counting method has some drift due to the hall-effect system, Periodically the battery ECU will dynamically adjust these figures to keep them accurate.

Click to expand...

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I have now logged 9 charging sessions with my Ray EV.
Sessions 1,2, 8,9 are 16A
Sessions 3,4,5,6,7 are Chademo

Each time I have recorded a triplog using Torque and calculated two values.
The first is the Ah Capacity of the pack as measured by the Cumulative Current Counter.
The second is the Ah Capacity of the pack as measured by adding up the battery current going into the battery each second.

I know the first value cannot be a measure of my existing pack, because it is greater than the value measured by the external stand.
In fact I believe the Cumulative Counters are calibrated to stay constant at the original usable pack capacity.



The high value each time is the original battery capacity.
The lower value is a calculation of the battery capacity now.
The difference between them is how much the BMS thinks the battery has degraded.
I assume multiple Chademo sessions in a row upset the calibration and deterioration looked much worse than it really is.
Session 7 in particular was a Chademo at lunchtime on a hot day.

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My latest project is to test the charging efficiency of the two cars (Ray and Soul EVs) with their differing cables.
Will the Soul EV charge at 16A more efficiently with a 16A cable or a 32A cable?
How bad is it to charge a Soul EV at 32A with a 16A cable?

The Ray EV comes with a J 1772 Cable that is recommended for 16A. (The cable is 3 * 2.5 mm2 and 1 * 0.85 mm2)

The Soul EV EV comes with a J 1772 Cable that is recommended for 32A. (The cable is 3 * 6 mm2 and 1 * 0.75 mm2)

It is possible to use either cable on both cars.I haven't collected the torque data yet, but the obvious difference is that the 16A cable gets quite hot, if you use it on the Soul at 32A.

I was puzzled why the cable has only 4 conductors, when the plug has 5 pins.
The answer can be seen in the slides here - j1772 Connector Conversion for Avcon Cables
The 5th pin has a cable coming from the handle of the connector itself. It means power will be cut when you press the button to release the connector, preventing any sparking.

Yes, PROXIMITY pin use the PE (Earth) because it's the GND of the 12v signal from the PILOT (1 wire from EVSE card from the supply).
PROXIMITY pin is only a set of resistor from GND level.

Almost all signals from a electric controller must be from the GND level (if you close an switch, you forward the GND to the correct entry of the controller).

And, Yes, the MECANICAL push button is an electrical button, too : it provide the ON/OFF signal for the onboard charger.

Soul EV have an signal on the dashboard if the Type 1 is plugged but the electrical button is stuck.
http://www.automobile-propre.com/forums/kia-soul-ev/mon-voyant-du-cable-de-charge-clignote-en-rouge-t5445.html

Try this : use tap to push the mecanical button on a type 1 plug ... and then, plug in the EV.
The charge indicator flash after 10 secondes ... because you don't have release the mecanical button (PROXIMITY pin is enabled, not a normal case after 10 seconds).

A spider's web have stuck my button.
And Torque help me to see this (and the Soul EV, too).