Aug 30, 2013
Timothy Thanks!
Yes, my part did start with the Greeks. Aesculapius to be exact, as mentioned in the Iliad.
http://premiumcaremd.com/wp-content/uploads/2013/08/Staff-of-Aesculapius.pdf
:tongue:�
Sep 6, 2013
richkae I have done a terrible job of accumulating the data and doing new analysis, I've gotten really lazy. I haven't even looked at the gmail account in a few months. I apologize to everyone who sent me email and expected a reply.
Partly it's because Tom has done such a good job with his PIA survey it seems redundant, partly I've gotten bored because my Roadster battery looks like it will last so long that it isn't interesting any more, partly because its annoying to extract data from email and then massage it every time.
So here is my plan. I am going to work on the vmsparser source code to do the following:
1) Read in an Excel file ( CSV ) database of all the data so far.
2) Read a set of log files and calculate the appropriate summary data for the car, identifying the car with a hash of the VIN#.
3) Add or update the data for that car to the CSV file and update the file.
So when you have a new set of logs that you think are interesting, you download the latest VMSParser.exe and the database file, you run the parser over your logs, it updates the database - then you upload the new database for all to enjoy.
If I wasn't an old C programmer I would make it all pretty and webby and 21st century. ( I might try, but first things first )
I'll also make a pretty Excel file ( real XLS ) that references the database and draws pretty charts, so that after you update it you can look at the pretty charts and see your car and compare it to the other cars. When you find something interesting you can post the charts here for all to see.
Sound good? So please keep gathering log files from your cars and hang on to them, and I will try to make headway on this when my real job doesn't interfere.
I'll also find a place to host the database. Suggestions welcome.�
Sep 7, 2013
dhrivnak Actually sounds awesome! We thank you! I guess the big thing we do not know about is will we continue to see a slight drop with time/miles or at some point is there a knee, or cliff in the data where the battery takes a dive. I feel certain that if there is a cliff it does not happen for 100,000 miles. Unfortunately I have seen many data sets that appear linear for a while and then the data hits a huge reflection point.�
Sep 7, 2013
JRP3 Most long term graphs that I've seen show capacity loss pretty much leveling off around 70%-80%�
Sep 8, 2013
hcsharp Aren't those graphs for just one cell? It's likely that it will be very different with the Roadster's ESS with 6831 cells. One cell won't suffer from failure runaway, but it's likely that you'll eventually see this problem with 99 bricks of 69 cells. There have been a few short discussions of this on TMC. Here's one:
http://www.teslamotorsclub.com/showthread.php/9572-Extreme-Long-Term-Model-S-Battery-Life?p=170910#post170910�
Sep 8, 2013
JRP3 Yes I'm talking single cell graphs and normal capacity loss. I'd say allowing an excessively degraded group of paralleled cells to cripple a pack is a maintenance issue, like running with a bad spark plug.�
Sep 10, 2013
hcsharp Wish I could replace a brick or sheet in the time it takes to replace a spark plug!
JRP3 you know a lot about where to buy cells. Suppose I had all the right tools and removed a sheet from my ESS and tried to replace the cells in a brick. Where would I buy them? Is it even possible to buy those 2200 mAh cells anywhere? Not that I plan to try this at home or anything...
�
Sep 10, 2013
stopcrazypp You can still find them on eBay if you search "Sanyo 18650". Or you can go to Alibaba, but it's harder to vet what's real and what's not and probably not worthwhile unless you are buying in bulk.�
Sep 10, 2013
JRP3 Yeah, I don't deal much with the small format cells, but I'd ask around at Endless-sphere.com Index page for a reliable source if I were looking.�
Sep 10, 2013
Smop Probably one of the most interesting threads on here....
I have had a chance to go over some of the logs of my 4 Roadsters and to my surprise the highest mileage one (22k miles) has the highest CAC. The others have 1/10th to 1/5th the amount of mileage as the one with 22k miles but are almost always charged on a 70A or 40A. I religiously charge the high mileage one on 110v and have had great results (192 ideal miles after a full balance). This could be just luck of the draw but it is interesting nonetheless. Would love to see some data for charge rates and how they relate to battery longevity.�
Sep 10, 2013
wiztecy I think its just a coincidence or just by chance that the BMB managed the higher milage Roadster better and possibly mismanaged the lower miles Roadsters. But then again maybe you're onto something with the 110v and BMB management. I'm on my 3rd pack, 20k miles on my Roadster, I looked at the CAC graphed on the previous 2 packs. On my first pack I saw two sheets that were low on aH capacity (majority of bricks were way lower than the rest of the pack). That pack was replaced due to an aux power supply gone bad. Had a refurbished pack that never charged back to the original CAC I had. I graphed that... same thing, two bad (low aH) sheets in the pack. Go figure after Tesla tested them! I now have a 3rd pack which has higher CAC than the previous two so I'm happy and things are looking good. I still have to graph this one, it has 150.75 CAC and its still growing... Tesla says this pack last had a 157 CAC when they last checked it, I really hope I can get that! Its recalculating every day and getting better. Pack was replaced about a month ago. I always charge at 240V @ 30AMPS.
Tesla say's that if you charge off of 110V it doesn't give the pack to properly balance and recommend 240V at 20+ Amps.
My feeling with the packs is that there're either bad cells / batches of cells in the bricks that pull down the sheets or most likely a bug in the BMB that's not doing the right thing when charging / balancing the pack. There appears to be Roadsters with 40K miles around with still 150+ CAC, so evidently they haven't hit that bug or had the bad bunch of cells.
I babied and did cool-down on my first pack... I noticed after 3 months after buying my Roadster with 3k miles the range dropping steadily. Lost 7 miles over three months and appeared to hold steady after the BMB was replaced on the side that managed the two bad sheets.�
Sep 11, 2013
JRP3 Another possibility is to use a higher amp hour cell. Since balancing takes place at the top of SOC those cells will simply never be as deeply discharged and the BMS shouldn't notice any difference. As long as the finish voltage of the cell chemistry is the same as the rest of the pack it shouldn't matter.
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It may be that the more frequently cycled Roadster simply gives the BMS more opportunities to balance the pack.�
Sep 11, 2013
qwk This is exactly what we have seen on here with roadster packs. 110V charging balances the battery better, and therefore you get a higher CAC, and ideal range. From my experience, my model S is following this same exact path(I charge it on 120V a lot).
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Who at Tesla said this?
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Yes. Using higher amp hour cells would just make each ideal mile last longer.�
Sep 11, 2013
wiztecy The service manager @ Menlo park.
Is it true what he said? I don't know but he did imply seeing Roadsters which have been charging off of the 110V circuit are typically out of balance. Possibly people are doing partial charges and the SOC is below 80% since 110v is very slow. Personally I don't see a difference with the balancing as long as the Roadster gets 30 min to 1 hour to balance after an 80%+ SOC charge.�
Sep 11, 2013
qwk I can see the partial charges being an issue, but as long as you do a standard/range charge every once in a while, cannot see the drawback of charging on 110, other than a slightly higher electric bill.�
Sep 11, 2013
hcsharp Yes if I did it I would use a higher Ah cell, especially since the price is almost the same up to about 3Ah/cell. Fortunately I don't need to replace any just yet! I noticed that you can buy Panasonic NCR but wow they are expensive!�
May 31, 2014
dhrivnak It looks like we have some new Roadster owners and if so please add your data to the Roadster owners Battery Study Plug In America
With 149 owners and more than 3.8 million miles it looks like the average Roadster loses about 3 miles every 10,000 miles. So after 100,000 miles youa re down to a 200 mile pack.
Personally my pack is on the low side but it has lost fewer miles over the last 23,000 miles.
I noticed that many of the early Toyota RAV4 owners have rebuilt packs. Hopefully that will be an option when that time comes.�
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