What's your 90%?

[jdw]

VIN 91991 @4200 Miles -90% rated is 240 and 100% rated is 265 with range mode off.

I was charging to 90% for the first month or so but lowered it to 70-80% in the summer thinking I was being kind to the battery. My range started to drop, so I did a couple "100% let it sit for a couple hours and run it down to 20% charges" and have been charging to 90% since. I don't always charge every day as I only use 10-12% in a typical day, so I figure I can be "kind" to the battery by letting it sit at lower SOC in between 90% charges. Pic from the last few minutes of my last 100% charge:

 

[bancroftc]

I took delivery on 10/14 and my 90% was 245.

Day 2 it was 244 and remained there for about a month. Just yesterday I think, I'm at 243.

1% drop in a month, but it sounds like that will stabilize (hopefully) after I drop a couple more miles?

 

[Sasmania]

I'm at 228 on a loaner pack...that started out at 245 at 90% on July 28th. This was towards the beginning of my road trip...almost 20,000 miles ago with mostly SuperCharging of course. But a pretty big 17 mile loss if you ask me for 3 months and 20K.

My original is getting fixed so we will see where that one is at when I get it back. Did just get back from the service center today and once again, GREAT service.

 

[badgerlake]

So after reading what wk057 had to say about balancing happening once the battery hits ~93%, I did a charge to 95% and then drove it over a few days until I got to around 50 rated miles left. Then I did a 90% charge. I did regain some miles -- went from 211 to 214 rated at 90% (but was at 206 not too long ago). Can't tell you how much was balancing vs recalibration but did gain some miles. I would love to get to 230+ but i'm not sure i'll ever get there w/ this battery.

 

[Sparrow]

I did the same thing that badgerlake did, which is to do some 95% charges, but mostly just 90% charging and I have now moved up from 205 2 months ago to 214 on a 90% charge.

 

[Todd Burch]

So I tested a few theories the last few weeks. Background: I typically do 5-10 range charges a year and normally charge to 90%, even on weekends if I don't drive the car much or at all.

My car has been at around 234-235 miles at 90% lately.

To determine the theory that running your battery down to a low SOC helps calibrate it, and to test the theory that charging to 100% (or >93%) helps balance the pack, I ran my car down to about 15 miles remaining one evening, then charged it up to 100% the next two days shortly before my 35 mile morning commute. Both days I let the charge finish completely (in case there was balancing at the end of the charge cycle).

The end result?

Before the test, my 100% charge was stopping at 260 rated miles.

The morning of my first 100% charge (after running it down to 15 mi remaining the night before), my car charged again to 260 rated miles. However, the number didn't start dropping until 4.5 miles later.This is equivalent to what I saw months ago.
The next day, my car again charged to 260 rated miles @ 100%. But this time, the range started dropping within about half a mile.

Now, a week later, my 90% charge stops at: 234 miles (probably the low end, it seems).

So not only did this not seem to improve the pack, it seemed to get a tad worse.

Conclusion? The confusion continues, as does the silence regarding an official word from Tesla about the range calculation.

 

[apacheguy]

Hmm. So if you charge to 90% daily it seems like there is little error in the range algo and also the pack seems to keep in balance.

I'm one of those who charged to much less during our hot summer, like 60-70% and saw a corresponding decline of rated miles. I wonder if repeating the test in my case would improve my numbers. Unfortunately this would have to wait until I road trip.

Agree that Tesla needs to come out with something. Owners are asking questions and getting confused. Their silence is frustrating.

 

[msnow]

Also, one of the top things people want/need to have confidence in, rated range can't be trusted.

 

[Todd Burch]

Hmm. So if you charge to 90% daily it seems like there is little error in the range algo and also the pack seems to keep in balance.

Except that I went 4.5 miles the first day before the rated range started going down.

I think I give up . I understand the range remaining is a bit of a guess-o-meter....just would prefer to hear from official sources how the guess-o-meter is guessing.

 

[Canuck]

So I tested a few theories the last few weeks. Background: I typically do 5-10 range charges a year and normally charge to 90%, even on weekends if I don't drive the car much or at all.

My car has been at around 234-235 miles at 90% lately.

To determine the theory that running your battery down to a low SOC helps calibrate it, and to test the theory that charging to 100% (or >93%) helps balance the pack, I ran my car down to about 15 miles remaining one evening, then charged it up to 100% the next two days shortly before my 35 mile morning commute. Both days I let the charge finish completely (in case there was balancing at the end of the charge cycle).

The end result?

Before the test, my 100% charge was stopping at 260 rated miles.

The morning of my first 100% charge (after running it down to 15 mi remaining the night before), my car charged again to 260 rated miles. However, the number didn't start dropping until 4.5 miles later.This is equivalent to what I saw months ago.
The next day, my car again charged to 260 rated miles @ 100%. But this time, the range started dropping within about half a mile.

Now, a week later, my 90% charge stops at: 234 miles (probably the low end, it seems).

So not only did this not seem to improve the pack, it seemed to get a tad worse.

Conclusion? The confusion continues, as does the silence regarding an official word from Tesla about the range calculation.

It's my understanding that doing this doesn't actually increase battery capacity. In fact, charging to 100% accelerates degradation as does letting the battery go really low. Both are hard on the cathode. So, assuming the algorithm is correct, you should see less range after doing this -- maybe not noticeable though if only done twice and you drive/charge right after doing it -- but it definitely won't increase range. It will only give you a higher reading if the algorithm was off. So I take from what you have done that the 85 algorithm is pretty good at estimating capacity.

 

[FlasherZ]

(EDIT: See Displayed Range and Seasonality for more data points and information.)

So I posted this in the 90D thread as well, but I spent some time today pulling the 90% range which appears to be seasonal... Here is my 90% charge taken from random days each month from January 2014 to today:

You'll see that the 90% tends to vary in a seasonal pattern - colder temperatures tend to result in less range, but I get it back in March and April.

In the middle of each month, I pulled the maximum 90% charge over a span of 2-3 days. I don't have time to correlate the temperature over those days (or look at software updates, or looked at in proximity to the last range charge for rebalancing), but you can see how the number varies seasonally. Note that the peak occurs in the spring, around Mar-Apr. This is the range data reported by the car via the API.

Keep in mind these are based on single samples from each month, so the data is very "noisy". If I were better skilled in MongoDB, I could pull every sample that was at 90% and graph it. But I'm horrible with it, and especially the nested document work that has to be done from TeslaMS.

EDIT: The range jump in Feb, 2014 was due to my battery pack replacement after contactors failed.

In addition, the high June, 2014 number was immediately after a week of range charging every day while on vacation, probably at the best balance the pack's had in a while. So there are other factors in play, but it appears to be cyclic with seasons here.

- - - Updated - - -

It's my understanding that doing this doesn't actually increase battery capacity. In fact, charging to 100% accelerates degradation as does letting the battery go really low. Both are hard on the cathode. So, assuming the algorithm is correct, you should see less range after doing this -- maybe not noticeable though if only done twice and you drive/charge right after doing it -- but it definitely won't increase range. It will only give you a higher reading if the algorithm was off. So I take from what you have done that the 85 algorithm is pretty good at estimating capacity.

For what it's worth, I've had my car at full charge for a few days at a time and my battery pack still charges to 266 miles on a range charge in the warmer parts of the year (262-263 in winter). The displayed range usually tends to go up after I've exercised the battery (balancing high, or taking it down and recharging).

 

[apacheguy]

It's my understanding that doing this doesn't actually increase battery capacity...

It may if the cells are out of balance. That represents true loss of capacity storage. Also, Todd was testing the range algo itself by following that procedure. In his case, the test indicated that the range algo was completely in check and the battery was perfectly in balance. The only loose end was the 4.5 miles he drove w/o seeing the range decrease.

 

[Canuck]

It may if the cells are out of balance. That represents true loss of capacity storage.

Really? I thought "true loss of capacity" is when the cathode degrades since there's no bringing that back. I thought balancing the cells is bringing back temporary loss, but not true loss, and in the long run causes damage to the cathode. But I'm no expert on battery issues.

 

[apacheguy]

Well, the cells need to balance in order to restore that capacity. You need to charge to 100% in order to do this. Ergo, range charging does in some cases bring back actual useable range. In the below quote, I assumed this represented range charging and I was merely pointing out the benefit.

It's my understanding that doing this doesn't actually increase battery capacity...

 

[JohnQ]

So I posted this in the 90D thread as well, but I spent some time today pulling the 90% range which appears to be seasonal... Here is my 90% charge taken from random days each month from January 2014 to today:

View attachment 101265

You'll see that the 90% tends to vary in a seasonal pattern - colder temperatures tend to result in less range, but I get it back in March and April.

In the middle of each month, I pulled the maximum 90% charge over a span of 2-3 days. I don't have time to correlate the temperature over those days (or look at software updates, or looked at in proximity to the last range charge for rebalancing), but you can see how the number varies seasonally. Note that the peak occurs in the spring, around Mar-Apr. This is the range data reported by the car via the API.

Keep in mind these are based on single samples from each month, so the data is very "noisy". If I were better skilled in MongoDB, I could pull every sample that was at 90% and graph it. But I'm horrible with it, and especially the nested document work that has to be done from TeslaMS.

I suspect I had a major software upgrade occur on Feb 22, 2014, when the range jumped from 225.9 to 240.1 from Feb-Mar. In addition, the high June, 2014 number was immediately after a week of range charging every day while on vacation, probably at the best balance the pack's had in a while. So there are other factors in play, but it appears to be cyclic with seasons here.

[

Great data and thanks for sharing. I'm jealous of your 90% charge after 3 years. I'm 2.5 years in and my 100% is only 2 miles more than your 90%

 

[badgerlake]

So after reading what wk057 had to say about balancing happening once the battery hits ~93%, I did a charge to 95% and then drove it over a few days until I got to around 50 rated miles left. Then I did a 90% charge. I did regain some miles -- went from 211 to 214 rated at 90% (but was at 206 not too long ago). Can't tell you how much was balancing vs recalibration but did gain some miles. I would love to get to 230+ but i'm not sure i'll ever get there w/ this battery.

Well that was short lived -- charged to 90% last night and only got 209 rated miles.

 

[NuclearPowered]

Great data and thanks for sharing. I'm jealous of your 90% charge after 3 years. I'm 2.5 years in and my 100% is only 2 miles more than your 90%

Have you contacted service about this? What have they said?

 

[JohnQ]

Have you contacted service about this? What have they said?

I haven't. It has been in line with some others who are at the "losing" end of the degradation bell curve. I'll discuss at my 3 year service in a few months along with my increasingly noisy motor.

 

[hanl1]

I took my 85D in September and it dropped from 245 to 242 in about 2 months and has stayed at 242 since.

I took delivery on 10/14 and my 90% was 245.

Day 2 it was 244 and remained there for about a month. Just yesterday I think, I'm at 243.

1% drop in a month, but it sounds like that will stabilize (hopefully) after I drop a couple more miles?

 

[CLLACAB]

I feel pretty good about our CPO that we picked up two weeks ago. At 90%, we are consistently seeing 234 miles.