Measuring battery degradation..

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FloridaSun

FloridaSun

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On a new Kona Electric, the SoC BMS shows about 95.0 to 95.5% when the SoC display is at 100%.
I made the assumption that the initial degradation will show the SoC BMS increase as the battery degrades. So, the last time I checked the SoC BMS at 100% was before 20k mile (I'm going to hit 30k miles today) and my SoC BMS showed 95.5% at 100% Display SoC. I just charged to 100% for a 300 mile road trip today and my SoC BMS has increased to 96.5%... 1% degradation.. So, if my understanding is correct, I still have 3.5% buffer remaining before my range will start decreasing.. Range shows 331 miles at 100% right now..

Interestingly, my voltage of the battery increased from over 10k miles ago.. It was 408.1 volt before 20k miles and it is 408.7 vots now. Max Regen at 100% is now 70.1kw while it was 71.0 kw at 100%
Screenshot_20200620-110716_Torque.webp
Screenshot_20200620-110508_MyHyundai.webp
 
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That's the way I read it as well, but I think its still important to correlate to periodic actual range tests under similar drive conditions. Unfortunately we don't have access the the Hyundai scan tools than can measure battery resistance and likely access to more pertinent variables. At best our imperfect tools and range test will give us reasonable guesstimates on degradation. It would be reasonable to expect degradation to be in the 1-2% per year range. Its not usual to see a larger degradation 3-5% in the first year and then significantly slower rate of around 1% there after. For whatever its worth my BMS SOC at 100% indicated charge was 95% when the battery pack was brand new 6 moths ago. It now reads 96.5 to 97% with roughly 13,000 km on the ODO. Most of my charge cycles have been 60-80% SOC from a A/C charger , with exactly 4 D/C charges.

Of an interesting side note that may or may not be helpful I see that Bjorn Nyland recently did some degradation/ range testing on his model 3 performance after 60,000 KM driving and he estimates( with help of "scan my tesla" obd tool) a 6% degradation. Now he also makes note over 60% of the KMs driven were DC fast charged and then compares to a similar battery capacity model 3 LR with similar KM but only 30% DC charging. That car only experienced 4% degradation. Hard to make any real conclusions with such a small sample size but their evidence is consistent with information that comes from sources like the battery university.
 
BlueKonaEV said:
... 95.0 to 95.5% when the SoC display is at 100%...
... SoC BMS has increased to 96.5%... 1% degradation...
Interestingly, my voltage of the battery increased from over 10k miles ago.. It was 408.1 volt before 20k miles and it is 408.7 vots now.
Click to expand...
So, the per-cell voltage at 100% displayed increased from 4.164 to 4.170 V, no-doubt reflecting that 1% further use of the BMS SoC.
 
apu said:
That's the way I read it as well, but I think its still important to correlate to periodic actual range tests under similar drive conditions. Unfortunately we don't have access the the Hyundai scan tools than can measure battery resistance and likely access to more pertinent variables. At best our imperfect tools and range test will give us reasonable guesstimates on degradation. It would be reasonable to expect degradation to be in the 1-2% per year range. Its not usual to see a larger degradation 3-5% in the first year and then significantly slower rate of around 1% there after. For whatever its worth my BMS SOC at 100% indicated charge was 95% when the battery pack was brand new 6 moths ago. It now reads 96.5 to 97% with roughly 13,000 km on the ODO. Most of my charge cycles have been 60-80% SOC from a A/C charger , with exactly 4 D/C charges.

Of an interesting side note that may or may not be helpful I see that Bjorn Nyland recently did some degradation/ range testing on his model 3 performance after 60,000 KM driving and he estimates( with help of "scan my tesla" obd tool) a 6% degradation. Now he also makes note over 60% of the KMs driven were DC fast charged and then compares to a similar battery capacity model 3 LR with similar KM but only 30% DC charging. That car only experienced 4% degradation. Hard to make any real conclusions with such a small sample size but their evidence is consistent with information that comes from sources like the battery university.
Click to expand...
Björn is not your typical driver. He fast charges a lot and often runs down the battery below 25%, sometimes even to zero. I'm rarely charging to 100% and I only went below 25% 4 to 5 times with 9% being the lowest. That's why I have little degradation. My Kona is most of the time between 60 and 80%. I do DC charge about 4 - 6 times per month.. The DC charging seems to have fairly little impact on degradation.
So far, I have not noticed any change in my range in similar driving conditions. I'm sure that my degradation is still less than the buffer size and therefore, I won't see degradation yet. At 1% loss per 30k miles, it will take over 300k miles before my battery capacity drops below 90%..
 
You can edit the display attributes of the cell voltages to make it a more useful two decimal places.
 
KiwiME said:
You can edit the display attributes of the cell voltages to make it a more useful two decimal places.
Click to expand...
I've tried to change the decimal places butbit won't let change it..
I get the following message when I try to change number of decinal places..

Screenshot_20200622-081155_Torque.webp
 
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