Battery University a good resource for battery info

I came across some interesting articles and research on the website below, covering a wide range of topics from battery use in EVs, to battery charging, temperature and depth of discharge usage characteristics:
http://batteryuniversity.com/learn/article/electric_vehicle_ev
http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

It is interesting to realize in Table 4 on the 2nd page referenced there, that with an 8 year "design" for EV battery life, that would lead to almost 3,000 charge/discharge cycles on the battery. To achieve that, it looks like the maximum cell voltage is reduced to achieve better longevity. With 192 batteries in our battery pack, they must be wired in a combination of series and parallel formats, to the equivalent of a series string of 96 sets of 2 parallel batteries, and a cell charging voltage of approx 3.95 VDC @ 84% charge (based on what I have noted as a charging voltage at a DCQC station of approx 390 VDC) ... which would indicate the batteries are only used to approx 60% (or less) of their fully usable capacity in order to achieve the approx 3000 charging cycles.

There is also lots of info on that website on cell phone battery tests and longevity ... all interesting reads for those who want to understand the batteries in our vehicles.

Thanks for the link - lots of interesting info.

This image helps me visualise why the Soul is advertised as 27kWh but has a real capacity of 30.5kWh
The spare capacity is hidden from the user at the top and bottom of the batteries charge.

It also seems to show why the driver would initially see a very slow degradation in range.
The loss is hidden in the reduction of spare capacity.
Also once the spare has gone it is probably sensible to be more cautious charging between 20% and 80%.

Note the image is a hypothetical example not the actual description of the Soul's battery.
Edit: if the image fails to display click http://www.batteryuniversity.com/_img/content/ev-driving-range-web.jpg

irfca said:

With 192 batteries in our battery pack, they must be wired in a combination of series and parallel formats, to the equivalent of a series string of 96 sets of 2 parallel batteries.

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Yes, I think you are right. According to the U.S. Advanced Vehicle Testing Activity the Soul EV has 96 cells.
We also know that the pack is built from 192 SK Innovation 38 Ah pouch cells with NMC (LiNiMnCoO2) cell chemistry.
The pouch cells are combined in pairs.

There's more details in the YouTube video here with Steve Kosowski. (Product Manager from Kia USA)

https://youtu.be/AtJ9GoYUPyU

This image is from the YouTube video above

From the Service Manual we can see how the 96 cells are laid out and numbered.



This becomes useful when we use an onboard diagnostic (OBD) tool to view the voltages of each cell.
(Soul Spy has not yet been written, but this is the kind of detail I would want it to show.)
These images are from Kia's Diagnostic Software.

Here's a picture of how the batteries are laid out in a real car.
Stack of 14 under the front seat. 10 then 10 in the footwell between front and rear seats then 14 under the back seat.
It will be the same on the other side of the car. 96 cells in all. 2 pouches per cell.

I guess JejuSoul wanted to upload this picture:



I documented the battery info of the Soul EV in a canadian forum 2 days ago as well, I put some pictures from the service manual there :

http://menu-principal-forums-aveq.1097349.n5.nabble.com/Specs-de-la-batterie-td33967.html

Direct link to AVT testing (which are good) : http://avt.inl.gov/fsev.shtml

Here's the specs from the manual:

SiLiZiUMM: the image I posted is an actual photo of the battery layout.
It is hosted on a Korean blog and does not always display here.
I edited the post to use a copy of the image I uploaded to tinypic.

Of particular interest - the position of the batteries is in the center of the car. They will not be hit by either a front or rear collision.

As per the data you shared i think you are saying correct. By the standard of Advanced Vehicle Testing Activity the Soul EV has 96 cells.We also know that the pack is built from 192 SK Innovation 38 Ah pouch cells with NMC cell.The pouch cells are also combined in pairs.

https://www.7pcb.com/

Wonder why they say the battery voltage is 350V, when a 4.06V x 96 is 389.76V.
My car, when fully charged, has a voltage of at least 395V, which means a capacity of more than 29kWh.

I love my Soul EV

goev said:

Wonder why they say the battery voltage is 350V, when a 4.06V x 96 is 389.76V.
My car, when fully charged, has a voltage of at least 395V, which means a capacity of more than 29kWh.

I love my Soul EV

Click to expand...

Hi

How do you know the voltage is at least 395V? If this is correct, than it is very interesting

Birkeland said:

How do you know the voltage is at least 395V? If this is correct, than it is very interesting

Click to expand...

I know because I asked the car
I used an OBD-II WiFi dongle with my iPhone and asked the car by sending request 2101 to 2105 on the can-bus. Then it'll give me all the info.
The format is explained here: https://docs.google.com/spreadsheets/d/1YYlZ-IcTQlz-LzaYkHO-7a4SFM8QYs2BGNXiSU5_EwI/edit#gid=0

I used EOBD-facile and its ECU -> terminal. Quite simple to use, but the decoding of the data is a manual job

Hopefully this will be a lot easier when SoulSpy Android App is available.

Elmil originally posted this in the Battery Ageing Model thread. I reposted it here, so I can reply in this thread. I'm reading through that journal article and some of the others cited in it. It's very theoretical. I want to keep the other thread for more practical comments about our data.

A nice diagram showing causes for battery ageing at anode and their effects: from Journal of Nanomaterials

A lot of information about EV batteries, especially regarding aging and temperature:
https://deepblue.lib.umich.edu/bits...Dissertation Final.pdf?sequence=1&isAllowed=y

This is an older general video about battery life and expectations:
https://www.youtube.com/watch?v=9yKe2DMnY1Q

And a recent video about range of EV's:

https://www.youtube.com/watch?v=cdplBU61wso

-
Some info about state-of-function (SoF).

From this page on the Battery University Site - http://batteryuniversity.com/learn/article/how_to_monitor_a_battery

Capacity is the primary indicator of battery state-of-health (SoH) and should be part of the battery management system (BMS). Knowing SoC and SoH provides state-of-function (SoF), the ultimate confidence of readiness, but technology to provide this information in an effective way is being improved.

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Then looking at this article for further info on SoF - click link to download pdf

“Review and recent advances in battery health monitoring and prognostics technologies for electric vehicle (EV) safety and mobility,”

...
SoF takes into consideration the weight of range of SOC, the charging.discharging rate, the environmental temperature, and other degrading influencing factors. In fact, how the battery performance meets the real power demands during battery operation is expressed by state-of-function (SoF). One of the ways to determine SoF is to calculate the ratio of the remaining accessible power in the battery module and the maximum possible power which could be stored in the pack ...

Click to expand...

ZuinigeRijder said:

A lot of information about EV batteries, especially regarding aging and temperature:
https://deepblue.lib.umich.edu/bits...Dissertation Final.pdf?sequence=1&isAllowed=y

Click to expand...

Thanks. There is 1 chart in that file I particularly liked.



This shows the deterioration for an NMC battery cell produced by EIG. - http://www.eigbattery.com/_eng/designer/skin/02/01_03.asp
The cell capacity completely collapses after 1100 cycles.
I am not sure how seriously to take this product. I don't know if it can be compared to the NMC battery by SK Innovation that we have. Look at the pictures below to see why.



They make cells for the Korean Golf Cart manufacturer CT&T. There are some amusing photos of this company's appearance at the Detroit Auto Show in 2010 - http://blog.caranddriver.com/korean-ev-maker-ctt-visits-detroit-says-annyong/

Here is also an interesting article with a lot of references:
http://www.mdpi.com/1996-1073/9/12/1025/pdf

Forecasting the State of Health of Electric Vehicle Batteries to Evaluate the Viability of Car Sharing Practices

Summarizing the results from the literature on EV Lithium-ion battery degradation, the capacity loss in lithium-ion batteries (CLLithium–ion) may be attributed to two main elements:

CLLithium–ion =(lcalendar,lcycle) (1)
where lcalendar stands for calendar life loss, which is the continuous slow degradation of the battery due to the passage of time, regardless of whether the battery is being used or not. lcycle stands for cycle life los, which depends on the chemistry of the battery as well as the way the battery is being used during charging and discharging.

lcalendar =(stemp,SoC) (2)
Furthermore, the calendar life loss is considered to be largely affected by the storage temperature (stemp) and the charge state (SoC):

lcycle =(crate,btemp, SoC, DoD) (3)
while the cycle life loss is considered to be affected by four main interlinked factors: the charging– discharging current rate (cr), the battery temperature btemp, SoC, and the depth of discharge (DoD):

These parameters seem to be interlinked, and it is difficult to exactly quantify the individual impact of each of them

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There was looked at how car sharing affects the SOH:

Considering the recharging practises, the co-housing members tended to recharge the shared EV prior to use (same day, in the morning) or late in the evening (if they were planning to use it early next morning). The car-sharing company members were obliged, as previously mentioned, to plug in the vehicle for recharge after every use (Figure 4). In the same manner, the EV would not be unplugged from the charger until the next user shared it, and this sometimes could take more than a week (Figure 5)
....
However, considering the battery SoC, it is evident that, in 20% of cases, the car-sharing company’s vehicle was recharged, but its battery SoC was higher than 90%. Almost always, the battery was left to fully recharge. For the co-housing members, the EV battery was fully recharged only half of the time, while the values of the SoC, at which the battery was plugged in for recharging, were more evenly distributed (Figure 8)

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And the conclusion is that

On a scale of five years (a typical battery pack warranties), this would mean that the battery of a vehicle shared by a car-sharing company will reach its theoretical end of life limit more than a year sooner than the one shared in a car-sharing practice similar to that of the co-housing community.

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This is a great article about Battery Lifetime: https://cleantechnica.com/2016/05/31/battery-lifetime-long-can-electric-vehicle-batteries-last/

What shortens lithium battery life?
- High temperatures.
- Overcharging or high voltage.
- Deep discharges or low voltage.
- High discharges or charge current.

Click to expand...

A number of benefits appear when an electric vehicle battery is sized for long range. A larger-capacity battery results in a lower average depth of discharge and consequently longer cycle life and lower peak charge/discharge rate. If maximum charge is limited to 80% under everyday driving conditions, maximum voltage is avoided. If the battery pack is also thermally controlled, both maximum voltage and high temperatures are avoided. In this way, controlled conditions can increase battery life substantially.

Click to expand...

My take-away for the Soul EV is that it is better to charge to 80% in general and do not drive near empty, but often recharge to 80%. In my daily driving practice I only charge at work, so from 80% till 40% next day. So it might be better to charge at home from 60% to 80% just before leaving the next day, because this increases the number of recharge cycles possible with the battery pack. A different chemistry is used in the Kia Soul EV, so the figures may be different.

irfca said:

I came across some interesting articles and research on the website below, covering a wide range of topics from battery use in EVs, to battery charging, temperature and depth of discharge usage characteristics:
http://batteryuniversity.com/learn/article/electric_vehicle_ev
http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

It is interesting to realize in Table 4 on the 2nd page referenced there, that with an 8 year "design" for EV battery life, that would lead to almost 3,000 charge/discharge cycles on the battery. To achieve that, it looks like the maximum cell voltage is reduced to achieve better longevity. With 192 batteries in our battery pack, they must be wired in a combination of series and parallel formats, to the equivalent of a series string of 96 sets of 2 parallel batteries, and a cell charging voltage of approx 3.95 VDC @ 84% charge (based on what I have noted as a charging voltage at a DCQC station of approx 390 VDC) ... which would indicate the batteries are only used to approx 60% (or less) of their fully usable capacity in order to achieve the approx 3000 charging cycles.

There is also lots of info on that website on cell phone battery tests and longevity ... all interesting reads for those who want to understand the batteries in our vehicles.

Click to expand...

Indeed the second article has some nice tables/figures: http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries


Figure 1: Capacity drop as part of cycling.

Table 2: Cycle life as a function of
depth of discharge. A partial discharge reduces stress and prolongs battery life, so does a partial charge. Elevated temperature and high currents also affect cycle life. Note: 100% DoD is a full cycle; 10% is very brief. Cycling in mid-state-of-charge would have best longevity.

Table 3: Estimated recoverable capacity when storing Li-ion for one year at various temperatures. Elevated temperature hastens permanent capacity loss. Not all Li-ion systems behave the same.

Table 4: Discharge cycles and capacity as a function of charge voltage limit. Every 0.10V drop below 4.20V/cell doubles the cycle but holds less capacity. Raising the voltage above 4.20V/cell would shorten the life. Guideline: Every 70mV drop in charge voltage lowers the usable capacity by about 10%. Note: Partial charging negates the benefit of Li-ion in terms of high specific energy.


Figure 5: Effects on cycle life at elevated charge voltages. Higher charge voltages boost capacity but lowers cycle life and compromises safety.


Figure 6: Capacity loss when operating Li-ion within given charge and discharge bandwidths.
Batteries charging to 85% have a longer life span than enabling full charge. Although longer lasting, a less than full cycle does not fully utilize a battery.
• 75–65% SoC offers longest cycle life
• EVs use 85–25% SoC to prolong battery life
• 100–25% SoC gives long runtime, makes best use of battery, but reduces battery life.