Battery Degradation Experiences

[MdlSP100D'16]

I have seen data online about percentage of swapped batteries on different EV’s including Tesla. But the absolute main part in early battery life have to be other failures from hardware like the BMS or mouist intrusion etc.

I think we see a number of batteries getting old and causing fault codes right now on the forum on model S out of warranty that probably is degradation related.

Initially, for the first five or eight years or so, the calendar aging/ age is the (very) dominating factor in degradation.
High SOC wear more and higher temperature wear more.

The cycles counted in throughput is usually referes as Full Cylcles Equivalent (FCE) in the research. It is more to it than the throughput or FCE.
Larger cycles wear more.
Cycles positioned at high SOC wear more.

Small cycles at low SOC generally gives the best throughput or number of FCE’s.

Low SOC in the regime where we normalky can use the car (0% displayed and up) do not cause increased wear.
It is the high SOC part of a cycle that is causing increased wear.

The research with Panasonic 18650 NCA cells show us that they can do about 700 cycles from 100-0% (4.20V - 2.5V/cell) with the current or C-load comparable to a highway driven car before the cells lost 25% capacity.

Thats 700 cycles from 100% displayed until the car stops and can not drive.
This would be about 700x400km = 280K km on the average model S, or 175K miles.
This test is of course performed in a short timeline, would take about 7-9 months to complrte the test so not much calendar aging.

If the charge level was reduced to about 90% (4.1V) but still down to 0%, we get 850 FCE cycles (so about 950 single cycles) and if reduced to 80% we get about 1000 FCE (so about 1250 single cycles)

View attachment 965775

This is consistent with more or less all research. There is a lot of research showing the same thing.

This picture shows same type of cells cycled between 0% and different SOC,

3.7V = about 50%
3.8V = about 60%
3.9V = about 70%
4.0V = about 80%
4.1V = about 90%
4.2V = 100%
View attachment 965777

We can see that the low part of the cycle is not the bad part.
The lower the cycle is positioned, the lower the wear.

Pictures from This report, a good read covering the most parts and aspects.
That report is in line with litterally hundred other reports, so not just one of a kind.

Hell of a detailed answer, thank you so much for the detailed write up.As a lawyer I always love sourcing and the root information so I can review. I will definitely read into what you provided.

Is there a way Tesla, when they have my vehicle for the MCU2 upgrade, would be able to tell me what my level of degradation is?

 

[ResHacker]

Did you DIY this? Looking to do the same on my car with a used 100kwh pack

Nope, I let the shop do it, because I didn't know what all of the SW stuff needs to be done to make the car "think" to be 100D instead of 85D. I also wanted to test the battery right after the purchase whether everything is ok. It may be quite dangerous to buy "some" battery just off the Ebay and pull it home..

 

[ResHacker]

Hell of a detailed answer, thank you so much for the detailed write up.As a lawyer I always love sourcing and the root information so I can review. I will definitely read into what you provided.

Is there a way Tesla, when they have my vehicle for the MCU2 upgrade, would be able to tell me what my level of degradation is?

It depends on people you're gonna meet there.. If not, I'd suggest you to buy Scan My Tesla app + OBDlink LX dongle to get nice numbers about almost everything going on in the car.

 

[MdlSP100D'16]

It depends on people you're gonna meet there.. If not, I'd suggest you to buy Scan My Tesla app + OBDlink LX dongle to get nice numbers about almost everything going on in the car.

Ahh excellent! Will do! Thanks!

 

[ResHacker]

It's actually not the best precise way because it depends on the current BMS calibration but it's quick. You can also make a calculation to get this number out of the numbers the car can offer using this guide or connect to the API here.
Nevertheless the most precise way is to charge it to full and then drive slowly to 0% and see how much energy were you able to withdraw out of the pack.

 

[AAKEE]

It's actually not the best precise way because it depends on the current BMS calibration but it's quick. You can also make a calculation to get this number out of the numbers the car can offer using this guide or connect to the API here.
Nevertheless the most precise way is to charge it to full and then drive slowly to 0% and see how much energy were you able to withdraw out of the pack.

There is a way of predicting is the BMS is calculating the capacity wrong.

I have successfulle made this, both doublechecked with a 100-0% drive on my (now sold M3P) and also the latest, predicted my Plaids capacity to be 98.0 kWh when the BMS said 95.3kWh at delivery.
It needed a couple of weeks but ended up showing between 97.9 and 98.2 kWh.

I have done a couple of posts about this, will be back with the links.

 

[livesmith]

I've had my 15' 85D for about 3 months now. It came with about 306K miles. Now it's around 318K. I don't know it's history. The pack says it's 2015, but last I looked at the label I didn't know to check for the R1 at the end so I'm not positive if it's been rebuilt, but seems plausible it is original.
According to Tessie and ScanMyTesla, I'm around 19% degradation, about 66KWh usable, and around 2000 charge cycles.

 

[ResHacker]

I've had my 15' 85D for about 3 months now. It came with about 306K miles. Now it's around 318K. I don't know it's history. The pack says it's 2015, but last I looked at the label I didn't know to check for the R1 at the end so I'm not positive if it's been rebuilt, but seems plausible it is original.
According to Tessie and ScanMyTesla, I'm around 19% degradation, about 66KWh usable, and around 2000 charge cycles.

66kWh usable is insanely good result for such high mileage battery if it is the original one. And if you were also voltage capped (charging only up to 4,1V/cell), the pack is definitely NOT that much degraded.

 

[MdlSP100D'16]

I've had my 15' 85D for about 3 months now. It came with about 306K miles. Now it's around 318K. I don't know it's history. The pack says it's 2015, but last I looked at the label I didn't know to check for the R1 at the end so I'm not positive if it's been rebuilt, but seems plausible it is original.
According to Tessie and ScanMyTesla, I'm around 19% degradation, about 66KWh usable, and around 2000 charge cycles.

If that battery is original that is INCREDIBLE for that amount of mileage!! Do you know if there has been any other work done on it??

 

[livesmith]

If that battery is original that is INCREDIBLE for that amount of mileage!! Do you know if there has been any other work done on it??

No, I really wish I knew it's history. Bought from a Ford dealer near Nashville. I figured out the previous owner was a Dr, tried contacting him through his website, but not unsurprisingly, never got a response.

 

[tesluv108]

I've had my 15' 85D for about 3 months now. It came with about 306K miles. Now it's around 318K. I don't know it's history. The pack says it's 2015, but last I looked at the label I didn't know to check for the R1 at the end so I'm not positive if it's been rebuilt, but seems plausible it is original.
According to Tessie and ScanMyTesla, I'm around 19% degradation, about 66KWh usable, and around 2000 charge cycles.

No way this is an original pack. How does the car drive suspension wise with that many miles? It’s too bad Tesla has taken the anti customer approach with the attitude they won’t share service records with the new owner of the car. How is that not relevant for the current owner ?

 

[livesmith]

No way this is an original pack. How does the car drive suspension wise with that many miles? It’s too bad Tesla has taken the anti customer approach with the attitude they won’t share service records with the new owner of the car. How is that not relevant for the current owner ?

I'm quite impressed with the handling. Very nice and solid. No roll like every other vehicle I've driven. That said, it needed lower front control arms and rear camber arms when i got it, though honestly I couldn't tell. And then last week I was putting the 21" wheels back on and realized the rear toe arms needed replacement.
Though on the driving note, the one thing that bugs me the most is that there is a mostly persistent vibration usually in the 45-55mph range. Definitely more noticeable on the 21's even with new tires, compared to the 19's which I bought used and apparently 3 out of 4 are still bent even after going through a straightening process. Doesn't matter if it's accel, decel or constant speed. and sometimes it's almost gone and sometimes it's really annoying.

 

[AAKEE]

I've had my 15' 85D for about 3 months now. It came with about 306K miles. Now it's around 318K. I don't know it's history. The pack says it's 2015, but last I looked at the label I didn't know to check for the R1 at the end so I'm not positive if it's been rebuilt, but seems plausible it is original.
According to Tessie and ScanMyTesla, I'm around 19% degradation, about 66KWh usable, and around 2000 charge cycles.

The total charge in kWh would also be available with SMT, do you have that number also?

 

[tesluv108]

I'm quite impressed with the handling. Very nice and solid. No roll like every other vehicle I've driven. That said, it needed lower front control arms and rear camber arms when i got it, though honestly I couldn't tell. And then last week I was putting the 21" wheels back on and realized the rear toe arms needed replacement.
Though on the driving note, the one thing that bugs me the most is that there is a mostly persistent vibration usually in the 45-55mph range. Definitely more noticeable on the 21's even with new tires, compared to the 19's which I bought used and apparently 3 out of 4 are still bent even after going through a straightening process. Doesn't matter if it's accel, decel or constant speed. and sometimes it's almost gone and sometimes it's really annoying.

How do you put 4k miles a month on your car

 

[livesmith]

How do you put 4k miles a month on your car

I use it for Uber 3 days a week and it's about 150 miles round trip to the heart of the business area. So about 250-300 miles each of those 3 days, total about 1k miles per week overall with my other job, etc.

 

[livesmith]

The total charge in kWh would also be available with SMT, do you have that number also?

 

[livesmith]

No way this is an original pack. How does the car drive suspension wise with that many miles? It’s too bad Tesla has taken the anti customer approach with the attitude they won’t share service records with the new owner of the car. How is that not relevant for the current owner ?

Dunno for sure if it's original but just verified the battery tag says it's a 2015 and does NOT say rebuilt/R1...
I should do the math on almost 2000 cycles... the trip meter when I got it had 350wh/miles average for the last 100k miles...
Hmm... Well 66000(pack capacity) X 19500(battery cycles) / 350(wh/mile) comes out to like 367000.... so if I read that right and did the math right... that seems to me likely to be original, no?

 

[tesluv108]

Dunno for sure if it's original but just verified the battery tag says it's a 2015 and does NOT say rebuilt/R1...
I should do the math on almost 2000 cycles... the trip meter when I got it had 350wh/miles average for the last 100k miles...
Hmm... Well 66000(pack capacity) X 19500(battery cycles) / 350(wh/mile) comes out to like 367000.... so if I read that right and did the math right... that seems to me likely to be original, no?

Tesla is good at leaving the wrong labels on

 

[livesmith]

Dunno for sure if it's original but just verified the battery tag says it's a 2015 and does NOT say rebuilt/R1...
I should do the math on almost 2000 cycles... the trip meter when I got it had 350wh/miles average for the last 100k miles...
Hmm... Well 66000(pack capacity) X 19500(battery cycles) / 350(wh/mile) comes out to like 367000.... so if I read that right and did the math right... that seems to me likely to be original, no?

Oh wait, I'm off by like a factor of 10 for cycles so my mind I have no idea on the math.

 

[AAKEE]

Dunno for sure if it's original but just verified the battery tag says it's a 2015 and does NOT say rebuilt/R1...
I should do the math on almost 2000 cycles... the trip meter when I got it had 350wh/miles average for the last 100k miles...
Hmm... Well 66000(pack capacity) X 19500(battery cycles) / 350(wh/mile) comes out to like 367000.... so if I read that right and did the math right... that seems to me likely to be original, no?

Scan my tesla calculates the charge cycles by dividing the total energy by the current nominal full pack. Hence 2205.

IRL, the nominal full pack has been somewhere around the middle of the full pack when new and the nominal full pack today, so in these terms a slightly lower cycle number.
(Researchers use the FCE, which mostly use the initial capacity as the reference.)

The above just for reference. That pack probably has been in the car since new (total energy / driven miles) so it is really impressive!