how to: Battery degradation

[f205v]

My car is now 1 and 1/2 year old and 50.000 Km under the wheels.
I would like to understand how much the battery has degraded after this time/distance.
What is an easy and straightforward method to calculate it?

Thanks in advance for your suggestions.

 

[tyson]

Easiest way would be to run the car down from full and note how much power, in kWhr was used. Compare this from numbers when it was new. If you don't have the numbers from when it was new then you really can't calculate anything. You can guestimate based on known new pack usable energy but that's about it.

A quick note is that no matter what method you end up using you need numbers from when it was new to be truly accurate. And the mileage guessometer doesn't count for much.

 

[f205v]

Thank you @tyson !
Unfortunately I did not note down numbers when it was new, shame on me.

 

[tjhmax]

How about having noted your indicated miles at 80% when new versus now.
My Model S 100D started with 268 miles @ 80%. It steadily dropped to now after 23,000 miles to 259 miles @ 80%.
I also noticed that my Wh/mile has been dropping by at least 10% over the same time.

Any thoughts?

 

[GWord]

Divide the rated miles by the percentage of charge you took the reading at. Then compare that number against the nameplate rating of your car. This gives you an approximate measurement based on what the car thinks your total pack capacity is currently.

 

[Tam]

...How about having noted your indicated miles at 80% when new versus now...

The calibration slowly drifts away so 80% now is not the same as 80% then.

You might need to recalibrate your State of Charge algorithm first.

 

[Naekuh]

How about having noted your indicated miles at 80% when new versus now.

i came to the conclusion that this is not very accurate.
As it approximates everytime, and each update, that number changes. I lose 1 or 2 miles and gain.
Also, your driving conditions would have to be EXACTLY the same each occurrence. If you went 5-10 miles more, or had a bit more regen breaking, and it would invalidate it.

 

[tyson]

See the link below for info on the batteries. Nameplate rating is useless for most all of the packs. The 85 and 90 packs are hilariously off and all fall short which will skew your numbers leading you to believe you have far more degradation than you really do.

If you have 100% range numbers from new you could run the pack down below 10% and do a full charge on a wall or mobile charger and get an estimate but it's not very accurate.


Tesla Battery Charging Data from 801 Cars

 

[BestRadar]

In 27 months of ownership my Model S was originally 297 at full charge and at a recent full charge I had 268 so I have lost 10% in less than 3 years. Mostly 80% charging with home charger.

 

[whitex]

How about having noted your indicated miles at 80% when new versus now.
My Model S 100D started with 268 miles @ 80%. It steadily dropped to now after 23,000 miles to 259 miles @ 80%.
I also noticed that my Wh/mile has been dropping by at least 10% over the same time.

Any thoughts?

Rated miles at some % is not exact. For example, our rated miles at 90% (the only setting we use) varies based on outside temperature. When Seattle area got the cold spell this year, immediately noticed both Model S reporting "finished charging at" about 2 miles below what it was before. When it warmed up briefly last week, noticed the numbers go back up. On other occasions, the range at which the car stops charging varies for some other reasons by another 2-3 miles. Lastly, you have to see what the mileage is right when the car stops charging, as is discharges over time before it comes back up. For example, my P85D charges to about 225 at 90%, then drops to 219 before charging back up. When cold, I've seen it go as low as 217 before charging kicks in again.

 

[jerry33]

Tesla seems to mess with the Ideal miles much less (or perhaps not at all) compared to rated range. It's what I use. While the only really accurate way to tell is a 100 to 0 discharge, that's hard on the battery so you don't do it unless there is a real reason to do so (e.g the Nissan Leaf owners did this for their successful lawsuit).

 

[themacs]

My car is now 1 and 1/2 year old and 50.000 Km under the wheels.
I would like to understand how much the battery has degraded after this time/distance.
What is an easy and straightforward method to calculate it?

Thanks in advance for your suggestions.

I would simply take it into Tesla and ask them.
I felt my car was losing way too many miles. I took it into Tesla and they calculated it (I think from new) and told me I had a battery problem. They are replacing the battery now.