Electric700
Active Member
I'm very interested to know what caused the degradation. Is Tesla conducting any research into this? Also, did you e-mail [email protected]?
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I'm very interested to know what caused the degradation. Is Tesla conducting any research into this? Also, did you e-mail [email protected]?
hans
P631
Yes, of course I e-mailed ownership. I am way past that. They escalated it much higher, and the word came down that degradation is not covered and they would not do anything for me. Since it is "normal" degradation, they won't do any more research other than what they can see remotely. That's when I inquired about paying to replace the battery myself, and the quote is above.
The highest rate of degradation should be at first:
Development of High Power and Long Life Lithium Secondary Batteries
See that the shape of the curve in the second graph has a big drop at first, then it levels out. I am guessing that the 5% degradation you are seeing is well within the expected amount.
Development of High Power and Long Life Lithium Secondary Batteries
See that the shape of the curve in the second graph has a big drop at first, then it levels out. I am guessing that the 5% degradation you are seeing is well within the expected amount.
Where do you get 5%? It was 8.2% the last time I measured. Also, my graph is flat at the top and has a sudden drop; not a gradual loss. This loss was in well less than 100 cycles.
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I have it in writing (an official quote from the SC).
In fact, here it is. My address is wrong, so don't feel worried that I didn't redact it:
View attachment 32531
3.15 hrs to do what could be done in 90 sec. They should at least throw in the labor..h
Seriously, though, you should escalate this all the way to Elon before paying 45K.
Electric700
Active Member
It was replaced due to an internal failure in the pack that resulted in the car becoming immobilized right after stopping in a unloading area for what was planned to be a 30 second drop off.
It is painful to see the extreme fight the car will put up against being dragged onto a rollback when the parking brakes refuse to release. It was obvious that the items referred to as skates placed under the rear wheels where not designed to slide well on a very course asphalt surface when subjected to the weight of the Model S.
heh, sounds familiar. We were luckily able to get it jumped so that the car would finally go into neutral.
It was great to see 266 miles of rated range after the range mode charge completed and settled this morning on the replacement pack.
250/265 = 94.3%. Can't use 273 as your starting point as the 8 rated miles over 265 are effectively "bonus" range. It's not surprising that you saw a sudden drop in reported capacity. Estimating capacity without going through a full charge/discharge cycle is difficult.
Either way, it's splitting hairs, IMO, as Tesla is right. You're seeing what appears to be a normal amount of capacity loss given your car's age, mileage and climate.
Batteries should lose capacity fastest the first year. Looks like you are 11 months in and probably 20k+ miles?
IIRC, Tesla estimates 20% after 5 years and 30% after 8 years. You're right at 5% after a year and putting on many more miles than average, but I think you'll still come in under Tesla's estimates by the time year 5 rolls around.
At the very least - I don't think the Miami heat is helping much. At least with Nissan LEAFs, Florida vehicles lose capacity significantly faster than average and it appears that Tesla doesn't cool off the pack in the Model S until the pack gets pretty warm - certainly warmer than Florida temps. Remember, thanks to Arrhenius' equation, rate of capacity loss will double for every 10C increase in temperature.
If you want to maximize your battery life, it can help to keep the SOC as close to 50% as possible, especially in the heat and have the charge finish as soon as possible before you plan on driving.
Um, you posted an expected degradation chart. It doesn't account for "bonus" range. It is how each cell should degrade. Tesla's marketing promises have nothing to do with it.
I was talking about his attachment, which showed "normal degradation" which he said was equivalent to what I was seeing. On that post I was not talking about what matters to Tesla; only that he is wrong that I am seeing what the chart shows.
stopcrazypp
Well-Known Member
I once posted a degradation chart for the NCR18650A (which believe to be the closest to what Tesla is using) and there is a big drop from 3100mAh to 3000mAh within 5 cycles (about 1325 miles assuming 265 miles per full cycle). That corresponds to about 1% of capacity assuming a 3000mAh baseline (which is what I assumed back then). That may be part of what's responsible for the "bonus" range that people see in the car went it still has very little miles.
http://www.teslamotorsclub.com/show...evealed/page13?p=172284&viewfull=1#post172284
The rate after that is ~7.8%/100 cycles for 300 cycles and then ~1.35%/100 cycles afterwards.
I suspect your loss is still within the range of loss that qualifies as normal degradation (maybe below the average, but still not at the point of a defect). At 250 miles at 20k+ miles, I suspect Tesla sees that as within the degradation range and not a cause for a physical pack investigation yet.
If you look at the battery survey, at 20k+ miles, the typical number is 25x miles.
http://www.pluginamerica.org/surveys/batteries/model-s/vehicles.php
Actually, I posted that chart. It's part of a research paper that Panasonic submitted to a conference. It uses roughly the same chemistry as Tesla's batteries but they are not Tesla's cells. Also, the test environment is not the same as your real world environment. However, the shape of the curve should be indicative of expected performance.
As for charge cycles, I've been trying to find research literature that gives a better characterization of how small depth of discharge cycles add up to full cycles. The cycles shown in that graph are smaller DoD cycles than usual, hence it goes out to 3,000 cycles. I usually model 200 miles as the equivalent of a charge cycle for Tesla's battery pack, but that's a rough guess.
It seems to me that the $45k battery replacement given is a "go away" price. I don't think they expect to be replacing any battery packs until near the 8 year warranty on the 85kWh pack.
stopcrazypp
Well-Known Member
I use the "equivalent full cycle" method. As in two 50%DOD charges = one 100%DOD charges. This is more "conservative" (you likely will get less degradation using the former than the latter), but it characterizes the actual utility you get out of the pack quite well (which should be measured in units of energy).
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