Battery Degradation - 2014 vs 2015 Spark EV

[MrDRMorgan]

I just completed my first year of collecting battery degradation data for both my 2014 and 2015 Spark EVs. The values given below are the monthly averages for all charging sessions in the month of March.

March................2016........2017.......ODO:..Start / End
Battery Capacity....kWh.........kWh
2014 Spark EV......18.97.......17.72.............4483 / 9829 (note: I also see my full-charge range has dropped by ~ 5 miles )
2015 Spark EV......17.39.......17.58.............8410 / 16475

One thing I did notice is the degradation rate for the 2014 Spark EV seems to have slowed down for the last 6 months. It may have something to do with the mileage on the vehicle at the time the data was collected. If my mileage assumption is correct, then I should see the battery degradation rate for the 2014 Spark EV flatten out more like the 2015 Spark EV which has almost twice the mileage on the ODO.

 

[CCIE]

So, capacity on the 2015 has gone up a little?

 

[Jedi2155]

Keep in mind the 2014 and 2015 has significantly different lithium chemistries (2014 LiFePO4, 2015 LiNiMnCo) and thus different degradation curves.

 

[MrDRMorgan]

Keep in mind the 2014 and 2015 has significantly different lithium chemistries (2014 LiFePO4, 2015 LiNiMnCo) and thus different degradation curves.

Thanks. I am aware of that fact and have I been trying to figure out just how much battery degradation I can expect to see over time.

The Idaho National Laboratory has been testing the battery on four 2015 Spark EVs. The INL Static Discharge test reports show average battery capacity data at 400 miles, 4000 miles and 12000 miles. I looked at the data between 4000 and 12000 miles and it looks like one could expect the battery to degrade ~ 1 kWh per 10,000 miles. The same test performed on a 2013 Leaf between 5000 and 15000 miles showed ~3 kWh battery degradation per 10000 miles.

Recently, I have been trying to use the information on my local EVgo DCFC to make the calculation. The variability is significantly reduced but not eliminated. I charged at this location 12 times this month. One assumption I made is that the charger efficiency was about 97%. I take the capacity number as shown on the EVgo screen at the start of charging and subtract it from the ending capacity number. Then I divide the number of kWh at the ending point by the % difference between the starting and ending capacity points and multiply the result by 97% to get my battery capacity number.

Today I repeated the DCFC test but let the charge run to 100% - no one was in line waiting. The vehicle's trip meter showed 34.2 miles at 5.4 mi/kWh. This calculates to 6.33 kWh used. The 2015 Spark EV's energy Info screen showed 37% - 0% - 0% and 6.3 kWh used; the car was fully charged early this morning. The DCFC started at 63% and ended at 100% (37% used) but the kWh added was 6.56 which, if multiplied by 97% charger efficiency, gives 6.36 kWh. Close enough.

In March of last year my 2015 Spark EV battery capacity averaged 17.39 kWh at the end of the month with 8893 miles traveled. Today, 30 March 2017, my 2015 Spark EV battery capacity for March 2017 averaged 17.55 kWh with 16519 miles traveled; 7626 miles for the year.

In March of last year my 2014 Spark EV battery capacity averaged 18.94 kWh at the end of the month with 4766 miles traveled. Today, 30 March 2017, my 2014 Spark EV battery capacity averaged 17.72 kWh with 9829 miles traveled; 5063 miles for the year.

There is a difference in the two batteries and it looks like the 2015 battery is better. I will be continuing my testing for the next year to determine if I keep the 2015 or turn it back in. I already own the 2014. Both cars have been absolutely trouble-free and more fun to drive than I ever expected.

 

[d15b7]

I've been keeping an eye on my battery capacity the last couple of months. it's staying fairly steady between 17.4 and 17.5 kwh. mine's a 2015 with 19,400 miles on it currently. so far I'm very pleased with the (very slight) battery degradation of my car.

 

[SparkevBlogspot]

I want to stress that it's only a data point for DRMorgan, and it may not reflect 2014 vs 2015 in general. In addition, his 2014 doesn't have DCFC while his 2015 does, and the fact that he drove his 2015 more may indicate different usage pattern.

However, 2014 does degrade bit more from various posts in this forum. My 2015 shows 17.9 kWh after 17K miles, and I used TONS of DCFC, not to mention running it down low often. Just about the only thing I don't do often is to charge to 100%. I charged to 100% less than 10 times, because I live on top of a hill, and I'd rather use regen than friction brakes.

I have to wonder if charging to 100% degrade the battery more. Since cars without DCFC tend to want to keep maximum range possible, it could be that many 2014 without DCFC charge to 100% more often than the ones with DCFC. Given that CCS stations only started appearing in numbers since early 2015, it could be that many 2014 do not have DCFC, thus charge to 100% more than 2015+ models.

 

[MrDRMorgan]

I want to stress that it's only a data point for DRMorgan, and it may not reflect 2014 vs 2015 in general. In addition, his 2014 doesn't have DCFC while his 2015 does, and the fact that he drove his 2015 more may indicate different usage pattern.

However, 2014 does degrade bit more from various posts in this forum. My 2015 shows 17.9 kWh after 17K miles, and I used TONS of DCFC, not to mention running it down low often. Just about the only thing I don't do often is to charge to 100%. I charged to 100% less than 10 times, because I live on top of a hill, and I'd rather use regen than friction brakes.

I have to wonder if charging to 100% degrade the battery more. Since cars without DCFC tend to want to keep maximum range possible, it could be that many 2014 without DCFC charge to 100% more often than the ones with DCFC. Given that CCS stations only started appearing in numbers since early 2015, it could be that many 2014 do not have DCFC, thus charge to 100% more than 2015+ models.

No disagreement from me SparkevBlogspot. Short of having the Idaho National Laboratory periodically perform a static capacity test on our vehicle's battery, we can only try to estimate the battery capacity from data we collect and hope the variables average out. That is why I am only using monthly averages for my comparisons. I am more interested in seeing trends over time given no drastic changes in the way my cars are driven. I can say that almost all of my charging sessions are L2 and I charge overnight to 100%.

 

[Jedi2155]

As I charge almost exclusivelyat work, I get 100% charges regularly but the drive home means it doesnt stay there for very long.

 

[NORTON]

...Recently, I have been trying to use the information on my local EVgo DCFC to make the calculation. The variability is significantly reduced but not eliminated. ...

It still seems measuring charge data, especially DCFC data, is temp dependent.
When I am at a DCFC during hot weather the first thing I hear is the AC compressor and the 'radiator' fans spooling up. This is power that is not going to the battery pack.

As always,,, time will tell about "Battery Degradation".
We can theorize now. But 8 years from now is what matters. That's a long time.

 

[MrDRMorgan]

...Recently, I have been trying to use the information on my local EVgo DCFC to make the calculation. The variability is significantly reduced but not eliminated. ...

It still seems measuring charge data, especially DCFC data, is temp dependent.
When I am at a DCFC during hot weather the first thing I hear is the AC compressor and the 'radiator' fans spooling up. This is power that is not going to the battery pack.

As always,,, time will tell about "Battery Degradation".
We can theorize now. But 8 years from now is what matters. That's a long time.

I started collecting charging and air temperature data last year in March. Over a 20 day period last month, I charged 10 times at the same DCFC station. Air temperatures at the time of charging were relatively similar. The DCFC station is 11 miles from my home so I have to drive the freeway to get to the station.

My calculated battery capacity average for the 10 charging sessions was 17.60 kWh with a minimum of 17.17 kWh and a maximum of 17.94 Kwh.

Knowing that many variables affect the full-charge range on the GOM, I am also looking at the monthly average of the full-charge range values to see if that number will give me a clue.

I have charged - L2 and DCFC - my 2015 Spark EV 2LT 120 times over the last year and plotted the calculated battery capacity for each charge. Interestingly, the trend line is flat at about 17.7 kWh over 8200 miles [currently 16600 miles on the ODO]. I did the same for my 2014 Spark EV 2LT [121 sessions of L2 charging only] and the trend line dropped from 19.1 kWh to 17.8 kWh over 5400 miles [currently 9829 miles on the ODO]. It will be interesting to see if the 2014 trend continues to drop or flattens out like the 2015.

GM's warranty for the HV battery requires the battery to be replaced if the rated capacity degrades by more than 35% in 8 years or <100k miles - whichever comes first. In December 2016, the Idaho National Laboratory issued a static capacity battery test report for a 2011 Leaf's HV battery. One comment in the conclusion statement caught my eye:

"For vehicle battery packs, end-of-life (EOL) criteria is determined to be when discharge capacity or discharge energy degradation exceeds 23% of the rated value as specified in the USABC Electric Vehicle Battery Test Procedures Manual Rev 3 (publication pending)." The Leaf had 22,606 miles on the ODO at the end of the test. Maximum battery capacity had dropped from 21.0 kWh to 17.9 kWh in approximately 16,000 miles.

The same test performed on two 2013 Leafs driven 10k miles showed the measured average energy capacity dropped by approximately 3 kWh. In comparison, the same test performed on two 2015 Spark EVs driven 8,000 miles showed the measured average energy capacity dropped by approximately 0.8 kWh or 1 kWh per 10k miles.

 

[Pegasus]

We can theorize now. But 8 years from now is what matters. That's a long time.

Indeed. I suspect we'll be more concerned about rust and door dings at that point.
I for one am happy to have the 2014 (in a "collectible" Titanium color to boot) with its 400 lb-ft!

 

[Planerench]

Has anyone considered the gearing and torque output are two more variables that make a direct comparison of 2014 to 2015/2016 difficult? With a higher gearing the 2014 will have higher current flow for equal acceleration. I bought a 2014 for freeway commute to work; generally constant speed, little need for savage acceleration. I suspect city driving will not be as kind to me as a 2015/2016.

 

[NORTON]

... are two more variables that make a direct comparison of 2014 to 2015/2016 difficult? ....

You may be overthinking this.
To roll any EV down the road it takes X kW.
At 30 mph - X kW.
At 75 mph - X kW.
Straight and Level, zero winds, standard temp.

Life is not that way....

Try duplicating a 25 mile commute for a few days and see if you get identical usage data. It probably won't be possible.
The EPA shows identical range spec for the two versions of the Spark EV.
That's 'close enough'...

 

[CCIE]

...
The EPA shows identical range spec for the two versions of the Spark EV.
That's 'close enough'...

Well, GM used the EPA cycle to generate a range spec. I suspect the EPA wasn't involved because that range spec is wildly inaccurate for the 2014, and also inaccurate for the 2015/16. Luckily for us it's inaccurate in our favor.

 

[MrDRMorgan]

Has anyone considered the gearing and torque output are two more variables that make a direct comparison of 2014 to 2015/2016 difficult? With a higher gearing the 2014 will have higher current flow for equal acceleration. I bought a 2014 for freeway commute to work; generally constant speed, little need for savage acceleration. I suspect city driving will not be as kind to me as a 2015/2016.

My 2014 Spark EV, at 12k miles, is giving me excellent performance in town. In 70 - 80 deg. F weather and 35 - 45 mph normal stop and go traffic, I am currently getting 110 - 115 miles of full charge estimated range. Having driven this car for the past two years, I know the full-charge range will start dropping as fall and winter air temperatures continues to decrease.

 

[Planerench]

Has anyone considered the gearing and torque output are two more variables that make a direct comparison of 2014 to 2015/2016 difficult? With a higher gearing the 2014 will have higher current flow for equal acceleration. I bought a 2014 for freeway commute to work; generally constant speed, little need for savage acceleration. I suspect city driving will not be as kind to me as a 2015/2016.

My 2014 Spark EV, at 12k miles, is giving me excellent performance in town. In 70 - 80 deg. F weather and 35 - 45 mph normal stop and go traffic, I am currently getting 110 - 115 miles of full charge estimated range. Having driven this car for the past two years, I know the full-charge range will start dropping as fall and winter air temperatures continues to decrease.

I have a 25 mile freeway commute so I wanted the 2014. Seemed tuned better to constant speed highway driving. I am getting used to variable battery capacity calculations though. A hard hill climb showed 16.5 kw capacity while 60 mph constant showed 19.5. I’ll see what averages out.

 

[MrDRMorgan]

Has anyone considered the gearing and torque output are two more variables that make a direct comparison of 2014 to 2015/2016 difficult? With a higher gearing the 2014 will have higher current flow for equal acceleration. I bought a 2014 for freeway commute to work; generally constant speed, little need for savage acceleration. I suspect city driving will not be as kind to me as a 2015/2016.

My 2014 Spark EV, at 12k miles, is giving me excellent performance in town. In 70 - 80 deg. F weather and 35 - 45 mph normal stop and go traffic, I am currently getting 110 - 115 miles of full charge estimated range. Having driven this car for the past two years, I know the full-charge range will start dropping as fall and winter air temperatures continues to decrease.

I have a 25 mile freeway commute so I wanted the 2014. Seemed tuned better to constant speed highway driving. I am getting used to variable battery capacity calculations though. A hard hill climb showed 16.5 kw capacity while 60 mph constant showed 19.5. I’ll see what averages out.

It is my understanding that the 2015 Spark EV battery was changed to a lighter LG battery and the gearing was adjusted for better highway performance. Since I have both a 2014 and 2015 and have run both on the freeway, my experience is that the 2015 gives slightly better performance on the freeway.

 

[CCIE]

It is my understanding that the 2015 Spark EV battery was changed to a lighter LG battery and the gearing was adjusted for better highway performance. Since I have both a 2014 and 2015 and have run both on the freeway, my experience is that the 2015 gives slightly better performance on the freeway.

It's the other way around. Because the 2015/16 have less power (400ft/lb vs 327lb/ft) they put lower gearing in. This improves acceleration, likely making up for the power loss. But, it means that the motor is spinning faster at any given vehicle speed.

Put another way, the 2014 had so much power that it could operate in "2nd gear" all the time. The 2015/16 operates in "1st gear" all the time.

So 2015/16 should be worse on the highway since the motor should be less efficient at higher RPM.

 

[ncerna]

I own a 2014 Chevy Spark. Even though it has less than 10,000 miles on it, my estimated range when fully charged is about 95 miles.

 

[MrDRMorgan]

It is my understanding that the 2015 Spark EV battery was changed to a lighter LG battery and the gearing was adjusted for better highway performance. Since I have both a 2014 and 2015 and have run both on the freeway, my experience is that the 2015 gives slightly better performance on the freeway.

It's the other way around. Because the 2015/16 have less power (400ft/lb vs 327lb/ft) they put lower gearing in. This improves acceleration, likely making up for the power loss. But, it means that the motor is spinning faster at any given vehicle speed.

Put another way, the 2014 had so much power that it could operate in "2nd gear" all the time. The 2015/16 operates in "1st gear" all the time.

So 2015/16 should be worse on the highway since the motor should be less efficient at higher RPM.

I found this which substantiates what you said:

"Of importance here is that GM had tested two different final drive ratios in the Spark EV. One, a 3.17 ratio, was eventually adopted for use in the production 2014 Spark EV. The other, a 3.87 ratio, will come standard on the 2015 Chevy Spark EV.

But that 3.87 ratio for the final drive is a significant alteration. The switch to 3.87 should increase city range for the Spark EV. However, in announcing that LG Chem will be responsible for the 2015 Spark EV battery (no longer is A123 involved), General Motors suggested that no MPGe or range ratings will change for 2015"

Here is the link to the full article: https://insideevs.com/2015-chevy-spark-ev-highlighting-changes/