JRP3
Hyperactive Member
Has anyone asked their specialist or anyone else directly what happens if you leave your car at the airport in the cold for X number of days?
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This makes a phenomenal amount of sense! Even at 2 miles/hour of charge after a few days it would really add up, not to mention keeping the car happy.
I have not done that, but I did submit the question to the "bulletin board" over on the Tesla forums. Maybe they'll post an official answer there.
<sarcasm comment="Just in case it isn't obvious...">
Now why would we do that? It takes all the fun out of speculating, extrapolating the worst from single datapoints based on early firmware, and then write scathing commentary on how this is a "deal breaker" and "Tesla Sux" as well as throwing virtual tantrums and stamping our virtual feet.
</sarcasm>
bonnie
I play a nice person on twitter.
I was told by the Scottsdale rep to email the Ownership mailbox with my "use case scenario" questions I had that they couldnt definitively answer. I don't know if or how quickly they respond not having contacted them in the past. But I'm going to try it for a few of my questions, including this one too.
Comparing the Model S's BMS operation to Roadsters may prove to be misleading. I suppose it depends on what you consider high SoCs, but a number of Model S owners have reported in this thread that when plugged in in Standard mode the car repeatedly "tops off", never letting the rated range drop below about 230 miles or about 87% SoC and it tops off to about 240 rated miles or 90% SoC. Obviously Tesla doesn't consider this relatively "high" SoC to be problematic for the Model S because that is the preferred protocol that they recommend for the well being of the battery.
They do of course warn against repeated Range charging which takes the battery to 100% SoC.
Larry
Some cars must be behaving differently, my car routinely bleeds 40+ miles when left plugged in for 4+ days. If the Roadster is left in standard mode and left plugged in for the same amount of time, the ideal miles will stay constant. Some Model S vehicles do not behave this way-under the same circumstances.
It will be interesting to note if that is still the case when you are upgraded to version 4.1 of the software.
Do you believe that charging from an SoC of say 75% to 90% every four days or so, will be better for your battery than topping off from 87% to 90% daily over those same four days?
Larry
We're going to have to get into the habit of posting our current version in our signature. My v4.1-enabled car has never shown less than 229 miles when I've gotten into it into my garage, after being plugged in for days.
I believe that keeping the SOC between 40-60% is better for the battery, long term. Furthermore, less cooling/heating is required to keep the pack at a lower SOC. Bottom line keeping your battery between 40%-60% will maximize your batteries useful life. There is a small amount of degradation that takes place charging to 90% daily. This is just my opinion based on people I have spoken with and the research I have done.
I am running 4.0. It is my understanding that the Model S starts a charge cycle anytime the doors are opened or it senses the key fob within range- even after it has been sitting for days. If there is no interaction at all with the vehicle for several days then- I believe- it starts to bleed miles. Of course it all depends on how many days we are talking about here?
Perhaps it is better to store the car at lower SoC, but what about if you plan to drive the car on a regular basis. Do you discount the fact that charging from a low SoC to a full charge might contribute to more battery degradation than merely topping off? Isn't it possible that you are merely trading one type of battery degradation for another?
Larry
I'll watch more closely to make 100% sure, but short of me unplugging and replugging the charge cable, opening the door or bringing the key fob in range does not cause the car to begin a new charging cycle.
I've let the car go 5 days before without initiating a charge, and upon walking up to it, it had 235 miles of range on it. I haven't watched it like a hawk to see when it charges, but it does appear to "top-off" with v4.1.
This all depends on how many miles you drive- or plan on driving in a day. In my estimation if you have a solid handle on the amount of miles you drive in a day there is no reason to charge fully on a daily basis. I would be curious to look at your information that shows why charging from 40% to 60% to a full standard charge contributes more to battery degradation than topping off.
Johan
Ex got M3 in the divorce, waiting for EU Model Y!
While it may be better in theory to keep the SOC around 50% (even accounting for the fact that drawing power from 50% SOC may be a little bit more harmful than from higher SOC's) one one could argue the following in short: For people who drive that car only a little or moderately it won't really matter if you charge the way you describe or with daily standard charges, as the battery will still be in good health after 5-8 years, and at some point "shelf life" or "calendar degradation" i.e. ageing becomes more of the issue. People who drive a very high number of miles per year (50k+ miles/year) might have something to benefit, but will at the same time not be able to do this in practice since all that driving will require frequent charging to high SOC's. For further discussion and arguments see these two threads:
http://www.teslamotorsclub.com/showthread.php/11700-Charging-Approach
http://www.teslamotorsclub.com/showthread.php/10708-What-does-the-battery-degradation-curve-look-like
Johan
Ex got M3 in the divorce, waiting for EU Model Y!
I'm not saying it's wrong, I'm saying for all practical purposes it doesn't really matter probably. The Model S battery is larger than the roadster battery, it's a newer somewhat different chemistry, it has more sophisticated temperature management etc. The Panasonic cells are one generation newer than in the Roadster, this too could mean that they tolerate better to a lot around SOC's up to 90% (and the Voltages this impilies).
surfingslovak
Member
I think it would be better to let it discharge a bit, before charging back up. The difference in this particular case shouldn't be very significant though. The rationale is that the vast majority of the initial capacity fade will come from calender life degradation. Lower average voltage should help counter that somewhat, and that's why letting it discharge is helpful. Of course, cycling losses will increase by running a deeper cycle, but these losses will be negligible when compared to calender life degradation, especially at the beginning of the battery life cycle. That said, the most important factor will likely be cell conditioning or cooling. Battery temperature plays an important role when it comes to both types of losses. As others have noted, all these considerations are relative. Battery technology has been improving, and we are talking fractions of a percent per charge or drive event. To be clear, I'm basing the above statements on personal experience, and on the following NREL report: http://1.usa.gov/agingmodel
JRP3
Hyperactive Member
Don't forget the balancing factor, which only happens with a full charge. If only running between 40-60% your pack could get out of balance, reducing effective range. As previously stated an occasional full charge should take care of that, but I think that's one of the main reasons Tesla want's the pack always plugged in for a full charge.
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