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Normal Degradation or Calibration Error on 16' X75D

Normal Degradation or Calibration Error on 16' X75D

Took Delivery on a CPO (Used) X75D a month ago. Love the car, still getting used to the whole charging routine and what and how I should be charging. From what I read and researched, charge nightly to 90% seems to be the consensus. Must I do this religiously? Some days my commutes are only 20-30 miles leaving about 75% -80% left. Seems kind of ridiculous charging 10%~?

The other thing I am noticing is that the car is showing about an 8% (198 miles at 90%) degradation on the battery. I kind of find this hard to believe since the car only has about 17K miles on it. I'm getting 8% degradation by calculating what 100% would be and comparing to the rated mileage you get from a new X75D.

Any suggestions? I've read might be calibration error? Is the fix for this still to take the battery down to low digit miles and charge to 100%? Looking for some experienced knowledge here.

Makemark | 17 February 2019

I got a used 75D with about 30k miles. I have always seen about 202-204 miles on a 90% charge. I think the degradation happens when new and tapers off..

wang5150 | 17 February 2019

I usually charge to 90% during the week but I don't always plug-in each night. However, I do charge more often on weekends (home and superchargers) due to finding and making up reasons to drive it more often.

Original owner of X75D since August 2016 with 22k miles and 90% charge still shows about 212 miles.

Hope this helps!

paul | 17 February 2019

On your question of charging strategies:

Personally - for general commuting I don't let it get below about 30-40% in case I need to do an unexpected detour. So it gets charged every 3-5 days to 80%. You don't need to charge every day. For long trips, it goes to full.

Interestingly, there's a lot of conflicting information about the best strategy for car batteries. Talking to different people will give you different personal perspectives.

For example, there are some charts that show that doing more smaller charges makes your battery last longer:
https://batteryuniversity.com/learn/article/how_to_prolong_lithium_based...

Alternatively - there's a few people using tesla's as taxis and have ridiculously high mileage - without taking any special care (i.e. supercharge lots whenever needed) and without seeing much degradation. For example: https://www.teslarati.com/tesla-model-s-400k-km-250k-mi-7-percent-batter... and https://www.teslarati.com/tesla-model-s-reaches-200000-miles/.

Tesla used to say "A happy tesla is a plugged in tesla" - i.e. leave it plugged in.
Tesla also will eventually reduce your charge rate if you do too much supercharging.

Take your pick who you listen to. :-)

I think the only thing that is *really* known is that heat is the enemy of batteries, and that Tesla have *by far* the best heat management with active liquid cooling (e.g. my Leaf's battery cooks if I fast charge it more than once a day or over 75%). Charging at home via a relatively slow charger generates very little heat.

As to your comment about degradation rate - there is a *lot* of data about Tesla batteries. From this chart (https://electrek.co/2016/11/01/tesla-battery-degradation/), you can see that batteries do degrade a little more at the start, and then tend to level off. So I wouldn't worry about what you are seeing yet.

rexarat | 17 February 2019

Thanks for all the feedback. Seems like everyone has about 15-20 miles more than me at 90%, so I must be one of the outliers on the graph. I’m going to try to drain the battery to 40 miles or less and charge it to 100% and see what mileage I get, just to see if it some sort of battery calibration error. 8% seems just a little steep for initial degradation. Hopefully it does level off if this is the case. Will post my findings once trying draining the battery.