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Battery degradation report (Feb 2018 Build)

novox77

1.21 Gigawatts
Nov 25, 2017
1,640
3,550
NH, MA
tl;dr I see no evidence of any battery degradation in the 1.5 years (25k miles) I've owned my LR RWD.

I'm about to go on a road trip so I charged my car to 100% last night. This morning, I found the SoC reporting 325 miles. This is notable because as recently as this past August, my 100% charge was 306mi and 308mi on two full charge attempts, about a week apart.

My car was built in Feb 2018, VIN 0068xx. I charge to 60% during the warm half of the year. During this time, I don't schedule my charges. I plug in whenever I'm home. I have a 240V 50A receptacle in my garage. I have the car pulling only 20A because I also have a Model S in the garage on another 50A receptacle on the same subpanel that only supports 100A max. Rather than scheduling to not overlap, I just have both cars drawing 20A max.

Next month as I start to see my regen limited due to the cold, I will start charging to 80%. I will also start scheduling my charges so that my battery hits my charge limit (or comes close) when I'm ready to use the car in the morning. This way the residual heat in the battery doesn't go to waste and I have full regen.

When I first got the car in early 2018, I charged to max and was able to get 308 miles. A year later (Mar 2019) I had a road trip and charged to 100% again. Still 308. This summer (Aug 2019) I didn't have a road trip but decided to charge to 100% just to see what I'd get, mainly because I had read that we had gotten a firmware update that bumped it up to 325. But at the time of that firmware update, few people on the forums reported actually getting 325. And more recently, potentially correlated to the Shanghai fire incident and Tesla's "fix" for that, many Teslas saw a drop in range. So I charged to 100% to see how my car was affected, and I got 306mi.

What was unclear at the time was whether that 306 represented a drop from my previous 308, or if it was a drop from a theoretical max of 325. Because I never charged to 100% immediately after the firmware update that supposedly gave me more range, I don't know what my potential max was. But a week later, I charged to 100% again and this time got 308. It would seem like I never got the bump up to 325.

Very recently, I read on these forums that the range reported next to the battery indicator IS affected by driving habits. My understanding was that it was just hardcoded to some EPA rating of efficiency. Indeed for most of my ownership, when I set it to 60% charge, I got the same number: 186mi. Didn't matter if I pushed the car hard that day or not. Always 186 +/- 1mi. But recently people were saying that the range value is affected by long-term driving habits. So over time if you tend to be a lead foot, the SoC rating would account for that.

I tend to drive for efficiency, with the occasional hard acceleration to pass or thrill the kids. My lifetime efficiency (reported by the car) is currently 203Wh/mi. This is better than rated range, so if the formula has changed, I would expect to see the best case range for my battery.

As I said from the start, in prep for my road trip today, I charged to 100%. I fully expected to see 306 or 308 as my max range. But nope. Car is showing me 325mi! This would lend some credibility to the hypothesis that the reported range is not just a function of rated range. As this is the rated max range for the car, and I was able to charge to this amount, I have to conclude that if there's any degradation to my battery, it is very insignificant. I have on many occasions gotten more than 325 in physical miles from a single drive, so I know my actual range is higher than 325.

Based on the observations of my car, I would say that fluctuations/drops in reported range are more likely due to how the number is being calculated and less of an indication of battery degradation. Overall I'm quite impressed at how my battery is holding up. Naturally I'll continue to monitor this throughout the lifespan of my car and will update when I have more data.

-edit-
one change I didn't account for above is that I'm on v10. It could be v10 calculates range differently, and that's why I'm now seeing 325 instead of 308. But these numbers would not imply any notable degradation of the battery.
 

evp

Nerd
Nov 28, 2014
741
1,021
Arvada, CO
I recently saw my 90% drop from 279 to 263 fairly quickly. I don't know whether recent software updates had a role in that. Or maybe, I swapped the 21" wheels out for my winter 18" set and recalibrated. I'm going in for service in a couple of weeks (one year on the road and 25K miles on the odo) so I'll inquire.
 

ngogas

Active Member
Sep 19, 2018
1,725
1,108
Utah
Pretty sure the software changed something. Seems wide spread with threads all over here talking about it.
 

KenC

Active Member
Sep 4, 2018
3,623
3,290
Maine
I charge to 60% during the warm half of the year. During this time, I don't schedule my charges. I plug in whenever I'm home. I have a 240V 50A receptacle in my garage. I have the car pulling only 20A because I also have a Model S in the garage on another 50A receptacle on the same subpanel that only supports 100A max. Rather than scheduling to not overlap, I just have both cars drawing 20A max.

Next month as I start to see my regen limited due to the cold, I will start charging to 80%
So, you have an extremely conservative charging regimen. 60%SOC in warm months, 80%SOC in winter.
 

novox77

1.21 Gigawatts
Nov 25, 2017
1,640
3,550
NH, MA
Update: during my road trip this weekend I decided to charge to 100% at one stop. The SC stopped the charging when the SOC read 310mi. The battery visualization on the car and the app showed that there was still a sliver empty.

So charging at home got me 325mi, but the SC didn't want to push it that high....
 
  • Helpful
Reactions: KenC and gecko10x

1.21GW

Member
Jul 23, 2018
747
1,192
Michigan
I had the same 90% SoC drop from 279 to ~264 over a very short period last October. After that it has remained steady. (LR AWD)
 

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