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Roadster Owner Based Study of Battery Pack Capacity Over Time

richkae

VIN587
Jan 15, 2008
1,917
29
My car is almost 27 months old, and it has 17500 miles on it.
I have very little battery capacity loss over that time, I still get standard mode charges of 189 miles and range mode charges of 240 miles.

The community here at TMC provides us with a great opportunity to learn more about this issue.
I worked with Tom Saxton to add some features to his log parser. It is available here: http://www.idleloop.com/tesla/vmsparser/
If you run "VMSParser -b *.tar" and pipe the output into a text file, it will record summary data so you can make histograms for the following items:
1) charging amps
2) state of charge
3) ESS temperature
4) brick ah capacity average
5) time range covered
No GPS, speed or other identifying data is in the output.
Note that the interesting data is in the temporary section of the log file, so if you do not have a steady stream of log files ( one every 4 or 5 months ) then there will be some holes in the data but it is not a fatal problem.

If a great many owners from our community would be interested in getting the log parser, and generating the data and sending it to me, I will try to analyze it and look for correlations and relationships among those variables and battery capacity. It's very likely that I will add more variables to the parser and reissue it and ask for new data.
As soon as I have any interesting findings I will report them.

To send me the data, please just email the text file to teslalogdata at gmail dot com, please add the ideal miles you got at your last standard mode charge and range mode charge if possible.

Here are the histograms ( courtesy of Excel ) from my car:
The first is ESS temperature in C
temp.PNG


The second is charging amps in hours
charging.PNG


The last is state of charge in % of time
stateofcharge.PNG


Some possibilities in the future:
1) divide temperature into idle, charging, driving
2) divide soc into idle, and driving
3) add ESS power output
4) complicate it all by adding a dimension: state of charge vs temperature
 
Last edited:

donauker

Member
Sep 5, 2006
801
110
Sent my data through September 21.

After seeing standard mode charge completions in the high 150s some months ago I have seen an improvement back up to the low 170s. This is credited to firmware updates. I will be doing a range mode charge tomorrow and will collect a new log this weekend.
 

DZCPA

2.5 2011#1263 "NO GAZZZ"
Jan 23, 2011
34
0
San Clemente, CA
My 2011 Roadster 2.5 #1263 is almost 6 months old with 10,000 miles on it. It is my daily driver as I got rid of my Porsche 911 and Mercedes SL 500. I just love this Roadster!. I get 183 to 189 miles on a standard charge and 230 to 240 miles on a range charge.
 

tomsax

Member
Jun 19, 2008
901
119
Sammamish, WA
Great work, Rich. I'm in. I figure it's good for owners to be looking at this data so we can all understand battery lifetime issues better.

I hope others will submit data as there's nothing in there that gives away any personal info.
 

dhrivnak

Active Member
Jan 8, 2011
4,511
3,928
NE Tennessee
Will try to get a log to you

Thank you for doing this and I know this is a question near the top of every Roadster's list. I have been monitoring ideal miles for about 2 months now after a standard charge. I have never seen quite the ideal miles others see as I average 178. If I average my first 4 readings and the last 4 my miles went up from 176 to 179. I did take two long trips of 500 miles in 24 hours so I did several days of range charging. Maybe my pack needed that for some balancing.

How much data do you need? I have about 3 months of since the ranger pulled my last logs. Am I right they are cleared out after the download?
 
Last edited:

slcasner

Active Member
Supporting Member
Feb 20, 2011
1,389
939
Sunnyvale, CA
Am I right they are cleared out after the download?
No, downloading the log does not clear it. It is a constant-length buffer that wraps around.

However, in my car the log was completely erased one time when service was performed and firmware was updated. Other times when service was performed, with or without a firmware update, the log was not affected.
 

hcsharp

Active Member
Jun 7, 2011
3,427
1,511
Vermont
How old do you want a car to be before it is useful to send you data? I don't think you want new cars. Is this a one-shot thing you're doing now? Or ongoing project? Thx. It's very helpful.
 

tomsax

Member
Jun 19, 2008
901
119
Sammamish, WA
To add a bit to what slcasner said, there are two sections on the log file. The permanent section contains daily records with some interesting info all the way back to the car's birth day. The transient section contains much more detailed records about driving and charging for the last ~60 hours of driving. So, to get a complete record of your log data, you need to capture a log file every 50 hours of driving. How often that is depends on how much you drive, could be few weeks or a few months.
 

richkae

VIN587
Jan 15, 2008
1,917
29
This will be an ongoing project. I hope to continue until we learn something useful about how long our batteries will last.
I want to have good data to help make a battery replacement decision when the time comes.
The older the car, the better the data at this point. If your car is young, just make sure you grab and save a log file every couple of months.

There is a new version available, Tom and I have made some improvements: http://www.idleloop.com/programs/VMSParser_0.9.12.zip
It adds a histogram of miles per day, and adds more detail about the battery capacity.

I have data from 4 cars so far, not enough to learn anything yet.
 

richkae

VIN587
Jan 15, 2008
1,917
29
Yep, I got the data from Tesla 255, thanks. I have 5 cars worth of data now.
The sample size is still too small to do serious number crunching on, but I will try to adhoc analyze all 5 and see if there is anything interesting to post here. ( and see if there are any bug fixes we need to make to the parser to make sure it is providing good data )

More fun than my day job, but it'll have to happen in spare time nonetheless.
 

richkae

VIN587
Jan 15, 2008
1,917
29
Step 1: Use a USB stick to download log files from your car. Try to do so at least every 3 months.
Step 2: Download http://www.idleloop.com/programs/VMSParser_0.9.12.zip
Step 3: Put all your log files in the directory with the VMSParser.exe you extracted from the zip
Step 4: Run "VMSParser.exe -b *.tar >output.txt" in a command window.
Step 5: Email the file output.txt to me at the email address: teslalogdata at gmail dot com

Thanks a lot for helping with this project!
 

richkae

VIN587
Jan 15, 2008
1,917
29
Here is a chart comparing 3 different cars state of charge over time ( vertical axis is hours ):

3carcompare.PNG


The blue car has a usage pattern you would expect, lots of time at 85% but also lots of time between 40 and 85.
The red car has led a low mileage life so far, and spent most of its time at 85%
The black car appears to use the charge timer almost exclusively so that it is always driven immediately after charging - and sits at 85% very infrequently.

Which battery will last the longest? Only more data can tell.
 
Last edited:

tdevince

Member
Oct 11, 2010
97
0
Columbia, MO
I just had my first annual maintenance recently. The Tesla Ranger told me that the car will update the battery calibration if you take the car from approximately 80% charge down to 20% charge. However, this has to be done on a single key cycle, (i.e., do not turn the car off during this event). Then after your next charge, the battery capacity gets recalibrated. I haven't done this yet, but after one year and almost 12,000 miles, I'm still showing 192 miles on a std charge.
 

hcsharp

Active Member
Jun 7, 2011
3,427
1,511
Vermont
I just had my first annual maintenance recently. The Tesla Ranger told me that the car will update the battery calibration if you take the car from approximately 80% charge down to 20% charge. However, this has to be done on a single key cycle, (i.e., do not turn the car off during this event). Then after your next charge, the battery capacity gets recalibrated. I haven't done this yet, but after one year and almost 12,000 miles, I'm still showing 192 miles on a std charge.

Hard to believe that's accurate. If that were true, some cars would never get recalibrated. Lots of people drive from 80% to 20 but rarely on one key cycle. A rare event like that might help provide more data for the calibration software but I think it is calibrated much more often based on how many kWh you get when going from voltage point A to voltage point B.
 

rgjones

Member
Nov 8, 2009
30
1
San Diego
Just sent in my data for 2.0 sport @ 18k miles.
I've been using the Tesla Tattler for several months with the cooldown feature, which should show the battery spends more time at a lower temperature, but also at a lower state of charge. It will be interesting to see how this compares with the other logs.
 

cinergi

Active Member
Sep 17, 2010
2,176
41
MA
When I run it, the section for AH is empty ...

timestamp, brickahmin, brickahave, bricknumber
--------------
timestamp, firmware version
02/23/2032 20:15:15, 4.3.12 33

(as is miles per day)

milesperday, count
--------------

TeslaGLOP shows I started out with 157.62 AH and I'm now at 155.74 (13 months, 11,000 miles).
 

richkae

VIN587
Jan 15, 2008
1,917
29
When I run it, the section for AH is empty ...

timestamp, brickahmin, brickahave, bricknumber
--------------
timestamp, firmware version
02/23/2032 20:15:15, 4.3.12 33

(as is miles per day)

milesperday, count
--------------

TeslaGLOP shows I started out with 157.62 AH and I'm now at 155.74 (13 months, 11,000 miles).

Would you be willing to send your log files so I can debug? If you prefer, I will delete them as soon as I have fixed the problem.
 

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