Battery aging / degradation over time

[David99]

That graphic has been circulated several times around TMC. It is nothing more than informed speculation. Some folks have been able to pull close to 80 kWh while others only 70 kWh on a full charge. My guess would be that the range algo was poorly calibrated for those that only made it 70 kWh and if they had continued driving past "Charge Now" they would've had usable capacity remaining.

Exactly! I really wish people would stop reposting this graphic as it is totally made up based on guessing, but looks like something official from Tesla. There is evidence that this graphic is wrong. More importantly, battery capacity isn't a hard number. How much energy you can get out of a battery depends on how it's used.

 

[Troy]

I really wish people would stop reposting this graphic as it is totally made up based on guessing

It is nothing more than informed speculation.

The 75.9 kWh number is not a guess. It is based on calculations. If you assume you don't know this number and try to calculate it from trip data, in most instances you will come up with a number that is pretty close. For example, in message #54 MarcG said, after a trip in his P85D he consumed 252-2=250 rated miles and 74.6 kWh energy. P85D rated range on Tesla website is 253 miles. Therefore the calculation is this:

If 250 rated miles equals to 74.6 kWh
Then 253 rated miles equals to X

X= 74.6*253/250= 75.5 kWh (X= Usable battery capacity in a new 85 kWh battery pack until rated range shows zero)

In this instance the result was -0.4 kWh off. I did many calculations and the results can be +-0.7 kWh off but generally speaking, 75.9 kWh is a good average. One reason the calculation doesn't always work is because the trip counter doesn't include consumption when the car is in park mode. When reading data from the trip meter, that trip has to be uninterrupted without parking somewhere between the beginning and end of the trip. If you parked somewhere for a while, you can't use that trip data for measurements. Another reason is, the consumption number the car reports is a calculation, not an exact measurement. It is not always too accurate. A third reason is, range mode on or off makes a difference. However, if you calculated the following for lots of different cars, the results would be close to 75.9 kWh.

Battery capacity when new = EPA rated range * Trip consumption in kWh / Trip consumption in rated range

 

[Polly Wog]

I don't know how many people here saw this, but in the 550 mile record recently set, Casey recorded 76.8 kWh. I think this is the most accurate value we currently have of maximum usable battery capacity. It is more accurate than many other examples, in my opinion, because Casey clearly documented that he did not run any other controllable systems: No AC/Heat/Radio, etc.

 

[wga22]

I intend to track the batterylevel, ideal_battery_range, and battery_range, so I might understand exactly how much the battery loses range over time. All these values are available via the API.

 

[CHL]

There is significant energy lost by joule effect (heating) in the battery that is difficult to know and depending on how fast you drive.
Energy is the product of internal battery resistance x square internal current.
That explain a part of the difference between the theorical 85 kWh and the usable kWh

 

[Cocolane]

Greetings! I am new to the Tesla Club and new to this blog. I thank you all for your input. My wife and I are a tad concerned about overdoing things with the supercharger. Based on the comments in this thread, may I conclude that less supercharging is better...in general? There is a supercharger between my home and my work. It is very convenient to stop and supercharge on a regular basis...1-3 times a week. Any suggestions on how frequently I can SC? I have a model S60 with 30k miles.

 

[RobertF]

As a 75 software reduced battery to 60 degrades does it show up on the 60 info and statistics? The alternative would be that it reduces on the 75 and leaves the 60 at 60.

 

[David99]

Greetings! I am new to the Tesla Club and new to this blog. I thank you all for your input. My wife and I are a tad concerned about overdoing things with the supercharger. Based on the comments in this thread, may I conclude that less supercharging is better...in general? There is a supercharger between my home and my work. It is very convenient to stop and supercharge on a regular basis...1-3 times a week. Any suggestions on how frequently I can SC? I have a model S60 with 30k miles.

I have had my car for 3 years and used Superchargers for about 50k miles. I think I used Superchargers about 400 times. My battery degradation is exactly within the average. Supercharging doesn't seem to have a negative effect on battery life. There are many other people who have put a lit of miles on their cars using Superchargers. None of them show worse battery degradation. Use Superchargers as much as you need it, it's not going to hurt your battery.

 

[ecobon]

I have had my car for 3 years and used Superchargers for about 50k miles. I think I used Superchargers about 400 times. My battery degradation is exactly within the average. Supercharging doesn't seem to have a negative effect on battery life. There are many other people who have put a lit of miles on their cars using Superchargers. None of them show worse battery degradation. Use Superchargers as much as you need it, it's not going to hurt your battery.

It might degrade it more as it's well known that charging batteries slower put less demand on them. But, another thing to consider is that quickly charging and *using* the stored energy also places less stress on the cells as opposed holding a very high SOC for an extended period of time. I tend to feel that supercharging behavior is in line with a charge up to the levels needed to reach the next charger + 15% and then quickly using that energy. As opposed to daily home or destination charging that most people charge to 90% and it stays at that SOC for several hours or more!

Keeping batteries at 40-50% all the time is best for the battery's durability, but does nothing for its utility. I think if we use superchargers frequently and keep the lower SOC around 30% before charging again and then quickly use it and store near 50% the cells would be in very good shape. If that is even possible without much burden is very doubtful. Will our batteries be obsolete by the time they lose significant capacity? I am using mine very liberally as I feel that our cells will serve us well until a newer energy storage technology is offered.

 

[sorka]

Greetings! I am new to the Tesla Club and new to this blog. I thank you all for your input. My wife and I are a tad concerned about overdoing things with the supercharger. Based on the comments in this thread, may I conclude that less supercharging is better...in general? There is a supercharger between my home and my work. It is very convenient to stop and supercharge on a regular basis...1-3 times a week. Any suggestions on how frequently I can SC? I have a model S60 with 30k miles.

Would it not be more convenient to charge at home overnight as you won't have to wait for charging? One of the reasons I got my MS is that I can charge at home and at work and never have to stop in between (260 mile round trip commute).

Superchargers are really meant for long distance travel.