Lon12
Member
Yes. I see that as well. Not sure where the "unplug" is but I have heard that mentioned here and from Tesla store employees.
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Interesting, this can be due to individual cell reversal in a pack, reference. However, it seems like this is more of an issue with over discharged packs. Projecting my inner engineer: it seems like the SW would limit current to a safe value.
Are there other failure modes you are aware of?
int32_t
Tesla Spotter
Things have changed in the new manual, seemingly to reduce concern about the Model 3's lethargic battery heater (that's the cynical side of me), by making the wording consistent between the three models. The old S manual sinply said to keep the car plugged in at low temperatures if I recall correctly. I'm looking for an old copy now and will update.
EDIT: I could have sworn I had read about keeping it plugged in when cold to prevent the battery from getting its toes cold, but the 2015 manual I have also says not to expose Model S to temperatures below -30 for more than 24 hours at a time … and the 2013 manual I found here says the same thing. I must be making this up. Nothing about this wording has actually changed.
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2014 versions (5.9 and 6.0) say the same thing at the current one I quoted regarding temperature.
A plugged in Tesla is a happy Tesla.
In the Model S / X there are only two cases where power is drawn from the grid: when it's charging and when the heater/AC is running.
There is no other situation where the car will ever draw any power from the grid when plugged on. It's misleading to say that a plugged in Tesla is a happy Tesla. It makes perfect sense to keeping your car plugged so you don't lose energy from the battery when you run the heater or AC and obviously when you don't plug in you can't charge the car. I recommend to always plugging it in!
But in terms of battery health there is no advantage to keeping in plugged in. The BMS works all the time regardless of power from the grid. The car will never take any power from the grid to do any battery health things that would otherwise not be happening.
There is no other situation where the car will ever draw any power from the grid when plugged on. It's misleading to say that a plugged in Tesla is a happy Tesla. It makes perfect sense to keeping your car plugged so you don't lose energy from the battery when you run the heater or AC and obviously when you don't plug in you can't charge the car. I recommend to always plugging it in!
But in terms of battery health there is no advantage to keeping in plugged in. The BMS works all the time regardless of power from the grid. The car will never take any power from the grid to do any battery health things that would otherwise not be happening.
Sure, but it will engage a new charge cycle when it has used a certain amount of power doing everything else in the vehicle. So the charge is a lump sum payment for all the small loads (wi-fi, cellular, 12V charger, passive entry, MCU, contactors (during 12v charge cycle)).
It also depends on whether a plugged in Tesla will run the pack heater (more) when cold. If it self protects, it will keep the pack above -30C for as long as possible, which, hopefully, is forever with grid power, but significantly less if self powered. I know I'd code that in, might even name the routine BlockHeater.
Unless something breaks or the temp is extreme, the thing that makes a Tesla sad is being low on charge. The only way to prevent/ correct that is to plug in. Therefore, a Tesla can be happy if not plugged in (high SOC), or sad if not plugged in (low SOC), but a plugged in Tesla is always a happy Tesla (and if not, it will be in a few hours).
stopcrazypp
Well-Known Member
There is no mechanism that causes permanent damage to the battery from sitting in cold temperatures. It can be damaged by charging in cold temperatures because this can cause permanent lithium plating on the anode, but this does not happen just sitting there.
The pack however can have accelerated degradation when sitting in high temperatures and high SOC.
EV-lutioin
Active Member
Depending on the electrolyte composition, it may freeze in the -40C range, which would be bad for the cells. Military batteries sometimes use a different composition good to -55C.
The other reason for the warning may be the effective capacity when at that temperature. If the pack voltage drops too low under load, the system may fault or produce extremely reduced performance when the driver tries to accelerate. Data from a different battery. Tesla cells may not follow this pattern.
1. Park in a heated garage
2. Time your charge session such that a deep charge finished immediately before your drive.
3. Own a car that has "max battery power" button, such that you can manually heat the pack. (Not on Model 3 LR)
Yes that doesn't cover a lot of use cases. But it is what it is.
navguy12
Active Member
Essentially, we are at the equivalent, EV wise, of what it was like to drive an ICE long distances in the cold in 1901.
stopcrazypp
Well-Known Member
This reminded me that there was already another thread that discussed electrolyte freezing and the Tesla warranty provision, but I never ended up finding a damage mechanism that occurs while the electrolyte is frozen:
Battery warranty and temperature below -30C (-22F)
From the mars rover link, the battery cells can be recovered by thawing and the temperatures they are talking about for their electrolyte being frozen solid is -60 deg C (-76F). They even tried freezing using liquid nitrogen -196C / -321F and able to recover. But they talk about medium SOC and no load. SOC is presumably the risk of overdischarge and the article references damage from discharging while electrolyte is frozen, but I never found a way that the cell would be damaged from discharge (only from charge) presuming the battery was not at low SOC and overdischarged.
Interesting, I assumed the issue would be the result of mechanical damage. Perhaps the degradation mode is some cells discharging while others are frozen followed by reverse current (causing plating) when other cells in parallel warm and activate? (frozen cells keep power then try to charge the cells that weren't frozen once things warm up)
edit: further thought: can a half frozen cell end up plating itself?
Thanks for the post as it forced me to go back and try to find my source. I could not find anything. When I first posted my question on another thread here it was based off of a manual that I had pulle from the web and when I typed the post I went back and forth to make sure I was reading everything correct. I just wish now I copied the link, but for the life of me I cannot find where in the manual I saw this now. Thus, my conclusion is I had to have mos read or interpreted what I saw.
Fortunately I have not allowed my car to experience this extreme as I never got an answer to my question on what would be a sufficient plug to use in these extremes. I travel a lot and when I am concerned with the temps for my upcoming trip I just end up taking a cab as there are no plug ins at the Calgary airport. Some park and rides offer plugs far a block heater, but those are on a first come basis and I just never wanted to take a chance.
So the question now becomes what does any Tesla owner do that lives in a climate where these extremes can be hit? Given that they have a store here and are selling lots of cars they must feel this is not a big issue but I don’t want to be the test subject.
Thank you for searching.
My personal interpretation/ hope is that the vehicle will keep the pack warm if it is plugged in. So while the environment is -30 C, the pack itself would not be (at least internally). Lots of variables with thermal conductivity, mass, SW, control. This edge case may be part of the snowflake addition to the UI.
int32_t
Tesla Spotter
That's what I'd hope too, but the wording doesn't say "good to -50˚C when plugged in," it says
And that sounds deadly serious.
Does anyone think it is likely that Tesla will utilize both motors in the AWD version of the Model 3 as battey heaters to improve heating performance of the battery pack?
I don’t think so because the battery’s coolant loop can only absorb so much energy at once and too fast of a rate of temperature rise will create uneven heating within the pack.
Model S/X dump huge quantities of heat from their motor and inverter into the coolant loop. This is not a problem.
Also managing this much heat with the coolant is not a unsolved problem either. Just imagine an ICE car that has ~300kW of output. If it's thermal efficiency is 15%, it's dumping 2MW of heat into the coolant loop at full output. Granted they can aim for 90C, but still a whopping 2MW!!!
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