Roadster Owner Based Study of Battery Pack Capacity Over Time

[richkae]

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


The second is charging amps in hours


The last is state of charge in % of time


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

[donauker]

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]

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]

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]

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?

[slcasner]

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]

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]

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]

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.

[dhrivnak]

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

Just checking to ensure you have the file from me from Tesla 255. If not send me a note. Thank you