Look Inside Kona Electric Battery And See Real Capacity

[KiwiME]

So, given that CDC, CCC and cell voltages are measurements and expected to be reliable we can deduce that the SoC derivation from that data needed correction. Have you checked the SoC and corresponding voltage against the LG Chem curve, referenced in blue on my graph above?

 

[KiwiME]

A final graph just for the record showing the contribution of regen. Net depleted coulombs in blue = consumed in red - regened in green.
Where the lines loop to the left is where I gain SoC on downhills.

 

[herode10]

So, given that CDC, CCC and cell voltages are measurements and expected to be reliable we can deduce that the SoC derivation from that data needed correction. Have you checked the SoC and corresponding voltage against the LG Chem curve, referenced in blue on my graph above?

I did check in the past the voltage vs SoC and it is scatter like yours. I will check against le LG Chem curve you presented. How can I get the data points of that curve?
This curve shows that in the last 5 % SoC, the voltage is dropping drastically. Given that the Coulomb are constant over the entire SoC range, this would mean there is a lot less energy per % SoC available in this last 5% compare to the first 95%. I never discharge my battery under 8%, so no data to confirm this.
Does this curve reflects the usable range of the Kona battery pack? There is talks that Hyundai keeps a buffer zone at both ends.

 

[herode10]

I did check in the past the voltage vs SoC and it is scatter like yours. I will check against le LG Chem curve you presented. How can I get the data points of that curve?
This curve shows that in the last 5 % SoC, the voltage is dropping drastically. Given that the Coulomb are constant over the entire SoC range, this would mean there is a lot less energy per % SoC available in this last 5% compare to the first 95%. I never discharge my battery under 8%, so no data to confirm this.
Does this curve reflects the usable range of the Kona battery pack? There is talks that Hyundai keeps a buffer zone at both ends.

Here is a voltage vs display SoC for a 100% to 11%:

 

[KiwiME]

Here's an image of the data I entered from the E63 cell datasheet. I don't think I can attach an .xls here, sorry, you'll have to type it in.

 

[herode10]

I discuss this in a previous post. I recorded a discharge from 100% SoC display to 11%. I plotted the Net energy used versus display SoC. Since the curve is not perfect linear, I did a 2nd order polynomial regression and obtain this result:




Using the polynomial equation, I create a table were I calculate the energy used for each % SoC as the battery discharges toward 0%. There are to much scatters in recorded data to obtain a linear result. The regression equation gives a much better result. Here is a snippet of this table:



Using the table, I calculated the delta energy between each %SoC to see many kWh in theory are used for each % SoC from 100 to 0 % Here is a snipped of it:



This table produced the following graph:



I don't have any data below 8% SoC so this part is pure theorical. This result shows that there is about 34 kWh available from 100% to 50% and 30 kWh left in the last 50% SoC.

 

[herode10]

Here's an image of the data I entered from the E63 cell datasheet. I don't think I can attach an .xls here, sorry, you'll have to type it in.

View attachment 12930

I replot my previous battery voltage vs SoC graph. I divided the battery pack voltages by 98 to give the average cell voltages instead. I added the LG OVC points on top of it.

 

[KiwiME]

That's even a better fit than I had. Perhaps I need to take a trip with less hills.

 

[herode10]

I pulled data from 4 different dates


The SoC value where the CCC and CDC counters passe each other has drift with time for me. I gather some data close to the date I got the latest BMS update and some others each months after that. I observed at least 2 time a SoC correction without any CCC, CDC, CED or CEC changes. I chose a point on March 10th and one on March 15th, since on March 15th I observed a 3% SoC correction. I can't explane this correction but it explanes some SoC shift at CCC and CDC crossing.

View attachment 12873

Yesterday, I was able to trigger a new SoC correction again. To acheave it, I start the car and turn off all accessories (climat control, radio, lights,...). I leave the car running as it for about 30 minutes. My SoC yesterday was at 39.5% and it suddently shift to 42.5%. The SoC where CCC = CDC was at 65.5% since July 2nd, with this SoC correction, it has moved to 68.5%. I drove about 3500Km since the last correction.

This seems to be a recalibration of the SoC based on some BMS variable. Since most of people will rarely leave their Kona turned On not moving for an extended period of time, this would mean that their SoC will be off calibration at some point?...

It would be interesting if someone else could try this.

 

[Carguy88]

Alright, alright, alright... I know it's been a few years since this topic has been discussed, but i truly just have one question that needs answered: Am I hurting my battery charging it to 100% every day knowing that there's most likely a factor of safety SoC on the high end?

I only stumbled across this thread because a Youtube review by two Hyundai techs of the Kona mentioned that it had an actual capacity of 67kWh and not 64kWh so it's safe to fully charge everyday.

 

[KiwiME]

Quoting "actual" v.s. "useable" battery capacity seems to be a popular subject among car journalists and some websites who are trying to appear that they have the inside scoop. Some manufacturers quote this as well but it's beyond me why since you can't access the full capacity. The technical term engineers use for this is "marketing BS".

Sure, the capacity is limited to about 95 to 97% but that's how EV manufacturers are able to offer a product using a lithium-ion battery that lasts longer than one in a smartphone or similar. That small margin results in achieving about 1200 full-charge cycles down to 80% SoH instead of perhaps only 400 to 600. There's nothing different about an EV battery other than that and far better thermal management.

Test cycle numbers are measured in a lab by carrying out repeated charging and discharging of cells over that specified application range. You can find these tests described in the cell datasheet. For example google LG Chem E63 for the early Kona cell.

Because one mode of degradation is related to how long the cell sits at any particular SoC, as owners we have the option to "game the numbers" by trying to keep the SoC away from the lowest and highest edges where time-based degradation is the highest. I'll emphasise that it's an option because rather than recognise opportunity some responders simply drop the mic and say "well, the car is leased so I don't care".

So, to answer your question, you're not "hurting" the battery by charging to 100% because it's been designed for this. But if you want to extend the life one easy way to do it is to add your own margins at both ends of the range.

 

[JoeS]

Alright, alright, alright... I know it's been a few years since this topic has been discussed, but i truly just have one question that needs answered: Am I hurting my battery charging it to 100% every day knowing that there's most likely a factor of safety SoC on the high end?...

For me, it's not a matter of "hurting" the battery as it is to maximize its lifespan with minimal degradation. This topic has been beat to death on virtually every BEV forum. Yes, every manufacturer has their own version of a safety margin at both the top and bottom end.

Battery longevity discussions can be separated into Cyclic Aging and Calendar Aging, with variables (e.g., Temperature) associated with each. Probably one of the best sources of information I've found is over on the Tesla Motors Club's forum, with a number of quite authoritative posters there with peer-reviewed backup information to support their assertions. I follow a gentleman named AAKEE on many threads there, and perhaps this thread (starting with Post #18 and a summary of links on Post #21) might help answer your question:
https://teslamotorsclub.com/tmc/threads/bestest-idealest-battery-charging-percentage-band.287025/

For myself, I keep my (wife's) Kona's SOC at 50%-60%, increasing that to 80%-90% just before a longer trip. My seldom-used 2013 Tesla MS85 has been sitting at 50%SoC (with a 13.6v float charger on its 12v so the car sleeps and never wakes up) for years and only gets charged higher just before taking off on a longer trip. At 130,000 miles its battery SOH is still >90%. It has been used exclusively for very long trips with lots of Supercharging, but I've never charged it to 100% and only rarely go over 90%SoC. OTOH, our two 2012 Mitsubishi i-MiEVs (EPA range = 62 miles, closer to 45 nowadays) are our everyday local daily drivers which often get charged to 100%, but, again, just before taking off as they are never allowed to languish at 100%.

 

[ChrisV2H]

Thx

I remembered opening another one a year ago. here are more pictures

Thanks for the battery photos Vid. Also resurrecting the old thread, do you know if there are any inline fuses in the HV junction box just behind the 2 HV connectors?

 

[electriceddy]

Thanks for the battery photos Vid. Also resurrecting the old thread, do you know if there are any inline fuses in the HV junction box just behind the 2 HV connectors?

3 displayed in this video, one each for PTC heater, HVAC (A/C - heat pump) and the 3rd for OBC (on board charger)

 

[ChrisV2H]

3 displayed in this video, one each for PTC heater, HVAC (A/C - heat pump) and the 3rd for OBC (on board charger)

Thank you for that video, very interesting. However apologies, I used the wrong terminology. I was interested in whether there are any fuses INSIDE the battery in the black box that both the HV connectors seem to feed into. I'm interested in whether there is any protection against short circuits in the cables between the battery and the HV junction box in the youtube video you posted.

Thanks again

 

[KiwiME]

Why not post a photo and point to where you mean? The only other HV fuses aside from where EE has mentioned are inside the battery pack itself and those are accessible from under the back seat.

 

[ChrisV2H]

Why not post a photo and point to where you mean? The only other HV fuses aside from where EE has mentioned are inside the battery pack itself and those are accessible from under the back seat.

Hi,
I've re-added the screenshot of the box I mean from my first post and also found this photo elsewhere of the box I'm interested in:

From the teardown here, I think it's the contactor box.

The fuse you mention under the back seat must be in the service disconnect plug, is it a single fuse, or are there 2 fuses for each of the HV connectors.

The reason I'm asking is that I'm repurposing a 64kwh battery pack and would like to know if the HV harnesses are protected from within the pack, or only at the point of the junction box which EE linked to.

 

[KiwiME]

I think the thread title "look inside Kona Electric battery" was figurative that than literal! Not many in an 'owners' forum would have intimate knowledge of the pack internals, certainly not me. You might want to try a DIY solar forum as this sort of thing is not what is normally discussed.

The 600A fuse mentioned below is the only fuse mentioned. From an engineering perspective I don't see why any more would be needed.

 

[ChrisV2H]

I think the thread title "look inside Kona Electric battery" was figurative that than literal! Not many in an 'owners' forum would have intimate knowledge of the pack internals, certainly not me. You might want to try a DIY solar forum as this sort of thing is not what is normally discussed.

The 600A fuse mentioned below is the only fuse mentioned. From an engineering perspective I don't see why any more would be needed.

View attachment 22840

Thanks for the reply, that schematic is very helpful. I don't want to go higher, far far lower. 25A is enough for my needs, I was hoping there might be a low power fuse on the HVAC HV connector to protect against cable damage outside the battery (rodent damage would be my primary concern!).

Thanks again