How do you calculate Battery Degradation?

g8mb1t

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Wondering how you could calculate the battery degradation to see the overall health of the battery and % kw available to use?
Does anyone know if you can take readings from carscanner and do a basic calc? Or FDRS. Even buying a secondhand MME this would be useful To know if the car was DCFC only which will impact the batteries performance. This could also be useful to know if something is up with your battery and sits outside the norm degradation as per warrantee.

 

generaltso

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The easiest way would be to use an OBDII adapter with CarScanner and look for the battery SoH value. Not sure how accurate it is, but it's something. The last time I checked, I believe mine was in the 98% range.
 

dtbaker61

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Wondering how you could calculate the battery degradation to see the overall health of the battery and % kw available to use?
Does anyone know if you can take readings from carscanner and do a basic calc? Or FDRS. Even buying a secondhand MME this would be useful To know if the car was DCFC only which will impact the batteries performance. This could also be useful to know if something is up with your battery and sits outside the norm degradation as per warrantee.

it is quite difficult to measure degradation in capacity as it has to be done at controlled temp and load to measure actual kWhr available from 100% to 5% or so since that is where the pack voltage starts dropping and you can determine the actual capacity available.

I really don't know how we'll be able to measure/prove degradation outside warranty, but it might be interesting to dig up the actual warranty language and test procedure that (will) be used. I would bet that capacity testing for warranty claims has to be done at 'room temp' for full charge and discharged under a specific load, perhaps on a dyno.

reading between the lines.... cold weather range reduction is NOT considered degradation
 

Nklem

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The easiest way would be to use an OBDII adapter with CarScanner and look for the battery SoH value. Not sure how accurate it is, but it's something. The last time I checked, I believe mine was in the 98% range.
Mine was at 93.5% after 12K miles and 7 months.... but zero loss in range or capacity from what I could tell. I do not know if it's an accurate point for determining anything. only 10 DCFCs to 80% in that time and 80%-90% charges on level 2.

I believe mine was at 94.5% from new with 11 miles as well.
 
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superdave80

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I have a clunky method using the Fordpass app (my EV driving logs plus charging logs). Pick a start time/date from a few days ago. In a spreadsheet, record all of the charging percentages, and see how much total percentage of battery you used during that time. Then under the driving logs, record how many KWh you used during this same time period. Divide the total KWh by the percentage used, and that will tell you how much battery degradation you have.

Example: Over three days, I used a total of 130% of my battery. Over that same three days, I used 87 KWH. 87/130% gives me 66.9 KWh at 100% charge. Since my 'original' capactiy was 68 KWh, my battery is at 66.9/68=98.4%. It's not perfect, but it should give a ballpark value.

Warning: Look carefully at your driving logs to look for any anomalies. Usually what will happen is the computer will forget to reset the trip mileage to zero, and that mileage gets added on to your next trip, so your efficiency will look better that it really is. Example: I had a 6.4 mile trip that used 2kwh (3.2 mi/KWh). I then had a short .4 mi trip that used .2 KWH (2 mi/KWh). However, in the trip log the 6.4 miles from the first trip was added to the .4 miles on the 2nd trip, so it showed a 6.8 mi trip on .2 KWh (34 mi/KWh, clearly not possible).
 

dtbaker61

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I have a clunky method using the Fordpass app (my EV driving logs plus charging logs). Pick a start time/date from a few days ago. In a spreadsheet, record all of the charging percentages, and see how much total percentage of battery you used during that time. Then under the driving logs, record how many KWh you used during this same time period. Divide the total KWh by the percentage used, and that will tell you how much battery degradation you have.

Example: Over three days, I used a total of 130% of my battery. Over that same three days, I used 87 KWH. 87/130% gives me 66.9 KWh at 100% charge. Since my 'original' capactiy was 68 KWh, my battery is at 66.9/68=98.4%. It's not perfect, but it should give a ballpark value.

Warning: Look carefully at your driving logs to look for any anomalies. Usually what will happen is the computer will forget to reset the trip mileage to zero, and that mileage gets added on to your next trip, so your efficiency will look better that it really is. Example: I had a 6.4 mile trip that used 2kwh (3.2 mi/KWh). I then had a short .4 mi trip that used .2 KWH (2 mi/KWh). However, in the trip log the 6.4 miles from the first trip was added to the .4 miles on the 2nd trip, so it showed a 6.8 mi trip on .2 KWh (34 mi/KWh, clearly not possible).

this doesn't tell you battery capacity/degradation, which was OP question.
this tells you charger efficiency.... sortof.
 

RickMachE

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this doesn't tell you battery capacity/degradation, which was OP question.
this tells you charger efficiency.... sortof.
Exactly my thoughts.
 

superdave80

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this doesn't tell you battery capacity/degradation, which was OP question.
this tells you charger efficiency.... sortof.
No, because charger efficiency would need to include the output of the charger from some charging app. Charger efficiency = KWh gained by battery/KWh output from the charger.
 

OldEVGuy

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Even buying a secondhand MME this would be useful To know if the car was DCFC only which will impact the batteries performance.
Recurrent offers this service. I remember seeing some discussion about it on the forum. As I recall, some people were concerned about privacy, since you need to give them access to your vehicle‘s data.

https://www.recurrentauto.com/
 

Maquis

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I have a clunky method using the Fordpass app (my EV driving logs plus charging logs). Pick a start time/date from a few days ago. In a spreadsheet, record all of the charging percentages, and see how much total percentage of battery you used during that time. Then under the driving logs, record how many KWh you used during this same time period. Divide the total KWh by the percentage used, and that will tell you how much battery degradation you have.

Example: Over three days, I used a total of 130% of my battery. Over that same three days, I used 87 KWH. 87/130% gives me 66.9 KWh at 100% charge. Since my 'original' capactiy was 68 KWh, my battery is at 66.9/68=98.4%. It's not perfect, but it should give a ballpark value.

Warning: Look carefully at your driving logs to look for any anomalies. Usually what will happen is the computer will forget to reset the trip mileage to zero, and that mileage gets added on to your next trip, so your efficiency will look better that it really is. Example: I had a 6.4 mile trip that used 2kwh (3.2 mi/KWh). I then had a short .4 mi trip that used .2 KWH (2 mi/KWh). However, in the trip log the 6.4 miles from the first trip was added to the .4 miles on the 2nd trip, so it showed a 6.8 mi trip on .2 KWh (34 mi/KWh, clearly not possible).

kWh per % varies by temperature - a lot. So unless you normalized the data according to actual battery temp/capacity curve, you can’t tell anything about degradation.
 

superdave80

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kWh per % varies by temperature - a lot. So unless you normalized the data according to actual battery temp/capacity curve, you can’t tell anything about degradation.
So what does it mean if my display shows 100% in warm weather, and 100% in cold weather?
 

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The simple answer is you can't. You can use a scanner and read the value from car which would the most accurate as that's what the car thinks it's battery health is. Getting the true state of battery would be near impossible without having very expensive equipment and access direct to the HV system. One of the reason for the difference between useable and actual battery capacity is give some headroom on degradation.

Most of the discussion here has been capacity degradation but is only one of the ways battery degradation is measured. Current degradation and standby loss degradation can also come into play.
 

daverp

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So what does it mean if my display shows 100% in warm weather, and 100% in cold weather?
It just means your car thinks it's 100% charged (or very close to it). Batteries are not like gas tanks, full doesn't mean it has 88kw of energy stored. Full is based off a peak cell voltage and does not directly relate to battery health. I worn battery can still reach peak voltage without storing as much energy. You'll start at 100 but drain quicker.
 

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I think people just need to enjoy their cars. I can't remember the last time I wondered how much less mileage I was able to get out of my ICE vehicle even those too lose efficiency over time.

 

 
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