Tesla owners in deep freeze discover the cold, hard truth about EVs

Chalo said:
you definitely have it.
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WE .. (as in my house) ..DO NOT have it !
..And the point is, this issue was widely reported by MSM, as well as multiple internet sources, youtube, etc etc,..so anyone suggesting this was a “Fake News” story need to get their head out of their a55 .
PS.. there are also reputable reports of folk driving their sub zero outside parked Tesla M3 into Supercharger station and instantly recharging at 230+ kW whilst still at -2F. !…
…BUT,.. that was after driving just 160 miles, (from 100% charged, to 2% charge),..so the pack will have warmed itself up before charging started.!
 
Here's the vid I was referring: [youtube]i-c8AUeKs5c[/MEDIA]

At aprox. 12:25, this Bozo burps the claim that he's, "just doing a test".... "this is an extreme case"... "something you'd never run into in the real world" (Vid was taken last year). Insert foot-in-mouth Bozo.

TeslaM3b-charger.png
 
neptronix said:
Wow.. 5kw isn't enough?

Imagine it takes both a long time to raise coolant from -15F to room temperature and then it takes a while for the cells to soak in the heat.
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I did a very quick google for calculators, and found this

Water Heating Power Calculator

This calculator tells you how much heating power is required to heat the water within a specified amount of time.
gettopics.com gettopics.com
but it won't let you use a start temperature below 34F. :roll:
I specified 2.4 gallons of water (a quick google says a model S has 2.38 gallons of battery coolant), 34F start and 72F end, with an hour to heat, at 50% efficiency (no idea how well insulated the pack is, but it's large surface area exposed under the car should shed heat easily if it's not sufficiently insulated against that.)

It says that it would take 446 watts over that hour, or 0.45kWh, to do that.

AFAIK it should take proportionally more to do it from -15F. So -15 to +34 is 15 + 34 = 49. 72 - 34 = 38. 49 / 38 = 1.3x the amount of power for the initial heating the calculator wont do. So 1.3 x 446 = 575W, and 575 + 446 = 1021W, or about 1kWh.



That';s assuming the battery actually is ever allowed to reach that temperature in a funcitoning car, *and* assuming the coolant can't freeze. If the coolant is frozen, it can't circulate. In that event, you can heat that coolant up to whatever the system limit is, then the heater will turn off. Then that coolant will pass *some* of it's heat to the beginning of the coolant pipes, but unless everything is very well insulated, the heat will radiate and conduct away from this point probably very much faster than it will ever be created by the heating system, because the system has to keep stopping the heating process to prevent overheating the coolant. (don't want to boil it and blow the system open from overpressure, or damage parts from heat).

If the heaters are not inside every coolant passage, then any temperatures low enough to freeze it, sustained long enough, will freeze the battery coolant in the unheated passages eventually, unless coolant is continuously pumped and heated the entire time the temperatures are that low. (which would use up the battery pack's power at some point). After that, you have to unfreeze the pack before you can even use the coolant heating system. :(
 
harrisonpatm said:
This is what I thought too. @neptronix , in other threads you and I have both agreed that we somehow want to build/convert our own EVs. What would you do for heating the battery during the winter?
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I'd want a fully air cooled battery for the lowest weight/size/complexity of the battery.

A prerequisite for me to own an EV is to have a garage i can keep to at least 32f which is the bottom limit of what you can charge a lithium ion battery at.

For handling discharge, i'd overspec the needed C rate by at least 4x what i'd need so that performance would be acceptable at freezing temps, but saggy below. I'd be happy to give up range for this.

This overspecced C rate would also ensure that the battery lasts longer as it ages and the IR goes up.. and also provide a few % better efficiency.

harrisonpatm said:
Point I'm trying to make is, why the heck does a Tesla need 2-5kw to heat the battery pack? Seems like way too much, in my experience. Granted, I don't know how it's currently done (I think I read once that it's pumped liquid throughout the pack?), but 2-5kw seems like way too much.
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A tesla battery is 2000lbs of liquid and metal so taking it to room temperature from -18f probably requires a crapton of energy.

Consider this, a 300 lbs ICE engine probably periodically produces ~25kw of heat and in below freezing conditions, it can take 5-15 minutes to get up to temperature while driving slow.

I don't see why the tesla battery pack has to hit exactly 60-70f to charge though.. why can't it gradually ramp up the power as the heating is happening..
 
Yeah, 30 minutes before charging starts, then it ramps up.

Of course, that doesn't sell ads for news channels. So instead it's "Motorists unable to power their vehicles!" It's a "CAR GRAVEYARD!"
 
neptronix said:
I'd want a fully air cooled battery for the lowest weight/size/complexity of the battery.
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It would also be easier to heat it in freezing weather, since there's no frozen coolant blocking the heating path. ;)
 
A few sources are suggesting that when cold, and prior to driving, the M3 motor(s) are run disengaged to load the battery for preheating. Clearly this lowers the SOC... AND requires extended charging times to replenish. Reads to me that preheating the battery is wasted energy, no matter how you slice it. Someone has to pay for it, and it obviously taxes the grid even more than just charging alone.
 
neptronix said:
i'd overspec the needed C rate by at least 4x what i'd need so that performance would be acceptable at freezing temps, but saggy below.
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How much performance do you need on freezing, icy, snow covered roads ?
Restricting power and performance in freezing conditions sounds to me like a good idea .
 
Hillhater said:
motors are “Run disengaged”….from what ?.
There is no clutch in the drive train.
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I do NOT own a Tesla product, so I admittedly know damn little (perhaps even less) about them. Likewise, many Tesla owners are, apparently,.. in the same ignorant boat.

"You can preheat the car by turning on the climate - it will warm the cabin and if it is cold enough, also the battery. The Model 3 uses the motors and inverters to generate heat which is circulated through the battery. Draws about 6kW to operate the battery heater and about the same for the cabin heater at full blast."

 
Papa said:
"You can preheat the car by turning on the climate - it will warm the cabin and if it is cold enough, also the battery. The Model 3 uses the motors and inverters to generate heat which is circulated through the battery. Draws about 6kW to operate the battery heater and about the same for the cabin heater at full blast."
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Yes, i understand they do have that (remote controlled), auto preheat function.
but it will only work if the battery has enough capacity left to enable it….No very helpful if your car is already at minimum capacity !
 
Papa said:
"You can preheat the car by turning on the climate - it will warm the cabin and if it is cold enough, also the battery. The Model 3 uses the motors and inverters to generate heat which is circulated through the battery. Draws about 6kW to operate the battery heater and about the same for the cabin heater at full blast."
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If you are going to a charger you don't need to do any of that. If the battery is cold and you are using the navigation system to get to a nearby charger, the car will start preheating the battery for you, without any input from you.

One of the problems Teslas had in Chicago was that people had parked their cars at the airport at low states of charge, expecting to charge as soon as they got back. Then they got back, drove without checking to a supercharger - and one of the superchargers near the airport was down. Had they used the navigation system it would have told them that, rerouted them to a nearby charger, AND preconditioned the battery.
 
Hillhater said:
How much performance do you need on freezing, icy, snow covered roads ?
Restricting power and performance in freezing conditions sounds to me like a good idea .
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I'm not saying change anything about motor performance.

I'm saying have 3x more battery discharge power than you need because in freezing temps, you'll have a third of the discharge power of whatever you had at room temp. Internal resistance of a battery moves up or down depending on temperature.

I used to run 20C lipo packs at 2C. 0.5v drop on the pack at full load at room temp, 1.5v drop at freezing... no problem with winter sag.. and 1-2% capacity loss in the cold.. that battery had zero temperature related stress.

Tesla's battery has zero such headroom and that's why it requires heating ( atrociously bad performance in cold otherwise ) and cooling ( their super high energy cells have high IR so they waste a lot of energy to heat, which you then must spend more energy cooling ).
 
I ran across the dreaded ford anti-theft system a few years back, Buddy's gf parked her car at my office, it being a ford was immediately broken into, all they did was jack up the ignition.

Turned out to be a god send, turns out there is an entire economy of legal owners fighting with the anti-theft system, so there are tonnes of options on what to do. I happily tore the existing key apart, dug the chip out, hot snotted it directly to the sensor ring and then changed the ignition.. problem solved.
 
neptronix said:
I'm not saying change anything about motor performance.

I'm saying have 3x more battery discharge power than you need because in freezing temps, you'll have a third of the discharge power of whatever you had at room tem
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Yes, and that is exactly what i meant.
motor performance is directly related to battery discharge power, so cutting the battery discharge power would limit the peak power of the motor…..a good thing on ice/snow
winter driving instruction 101…”light foot on the accellerator “ !
When would you ever need 200+ kW on ice/ snow ?
( unless your name is Stig Blomqvist ! 👍)
 
neptronix said:
*unless you got middle class to upper class money and somehow you have a garage etc.
Fairly big income divide in most big cities so this is unlikely.
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I understand that a cheap extension cord could get stollen but one of them would work fine.
 
Hillhater said:
Yes, and that is exactly what i meant.
motor performance is directly related to battery discharge power, so cutting the battery discharge power would limit the peak power of the motor…..a good thing on ice/snow
winter driving instruction 101…”light foot on the accellerator “ !
When would you ever need 200+ kW on ice/ snow ?
( unless your name is Stig Blomqvist ! 👍)
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It's not directly related, the controller's amp limits determine what your peak amps are. Battery determines what the volts are at a given C rate.

Lots of IR overhead is very important if you want to resist negative effects from temperature. Teslas have close to none.
 
neptronix said:
If that's a braille battery or something like it, do know that it has an insane C rate, so much so that if you cut the C rate in half from being weakened by weather, it still starts.

Teslas are the opposite. They're full of wimpy ~1C cells and tons of liquid to cool/heat them - a counter compensation for low C rate.

That's how they get such high range ^_^

I imagine these battery heaters were not up to the task of dealing with a rare moment of Antarctic weather. Or maybe not working at all?
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It's a Shorai motorcycle battery rated for a one liter engine, what they had on the shelf at the local bike accessory shop when I went in. I'm starting a 1.8 liter engine off it, this was its fourth winter in service. The selling point for me was it cost only about $75 more than the specialized little replacement lead battery, while saving 20 lbs. That's like one percent of the weight of the car.
 
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Hillhater said:
..if the battery cannot output the power,.. the controller cannot increase it
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The controller can increase it at the expense of ever dwindling efficiency... exactly like an electric motor.
Teslas's battery design favors range at the expense of power. The tradeoff's negative side is very visible here.
 
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neptronix said:
The controller can increase it at the expense of ever dwindling efficiency...
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Sorry,..but you are going to need to explain how a controller can increase abattery output power of say 100kW ( 300v, @ 330:A ) into some greater power ,…whilst losing efficiency ??
That sounds like the definition of a perpetual machine !😳
 
No, it's the definition of how batteries have always worked.

Let's start from the beginning.

You can extract more and more amps at the expense of efficiency until you hit a thermal limit.
Here is how progressive loading affects the Panasonic NCR18650B ( a cell tesla uses/used in the Model S; newer cells are similar )

1707590241795.png

Tesla picks a cell just like this and liquid cools it so they can both deal with high heat situations, and also extract significantly more power, at the expense of atrociously bad battery discharge efficiency.

Supercharging also abuses Tesla's battery beyond it's thermal limits, which is why the liquid cooling pump starts to run. it's generating heat while charging because we are experiencing sag while charging it.

This is all fine and dandy until we hit the freezing point.. the resistance of the battery is now triple.. in the chicago freak weather event scenario, it's quadruple.

1707590152036.png

Now we need that battery to be at room temperature to start accepting that rate of current and apparently a 5kw heater is not adequate to get that to happen in a reasonable period of time.

...but...

If we chose a cell that was strong enough to charge at the 2.5C at room temperature instead of 1C at room temperature, we need a fraction of the heating/cooling now..

Molicel P50B would be the perfect cell choice for this case because it eliminates the classic power vs capacity tradeoff:

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Hillhater said:
That doesnt answer the question.
How can a controller output more power than the battery can supply ?
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It appears that you just don't understand how batteries and controllers work. Or you are trying to confuse the board's newer readers. You have been doing this for years.
 
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