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Is pre-conditioning the battery bad for it?

WilliamG

Active Member
Apr 20, 2019
4,595
6,480
Seattle, WA
So here’s the situation:

In the 40-50F range, I’d warm my car up in the garage for about 20 minutes when I can, before driving. However, I’d still have regen limitation (dots) in the bar, often for 20+ minutes. Over the weekend, I was parked outside for a few hours in 38F weather. I warmed the car up 15-20 mins before I left for home, and even after the 25 minute drive home I still had some regen dots.

Now, this is where things changed. This weekend (again, pretty cold for Seattle in the high 30s in the evenings), when I preheated the car from the app - while it’s parked/charging in my garage, I came out to my car after 15-20 minutes of heating, and noticed the car sounded LOUD. Hmm, OK. I get into the car, pull out of the garage and notice I have 100% regen available to me. I had this happen on both occasions this weekend when I needed to drive.

So, it seems when it’s below a certain temperature threshold the car is pre-conditioning the battery in (I’m guessing here) the same way it does if you put a supercharger into the navigation. Is that what’s going on here?

Now, if there’s no downside to this pre-conditioning, why doesn’t it do this to heat the batteries up more quickly ALL the time, even in 40-50/60F weather? What’s the downside?
 

SageBrush

REJECT Fascism
May 7, 2015
12,781
17,024
New Mexico
Of course there are downsides -- you live in a world of trade-offs.
Heat is energy wasted, and batteries degrade faster with heat.
The advantages are your comfort, higher regen and charging, and less battery plating
 
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Kognos

Member
May 20, 2019
231
249
Portland, OR
Agree totally with SageBrush.

However I'm really curious about pre-heating the car in colder climates. I'm in Portland and haven't noticed what you've experienced from Seattle in ~30ish degree nights here.

I can't imagine there's a downside really. I tend to just trust the system. In the same way that the climate system doesn't actually blow warm air until the system is warm, in the (really) cold climates it might assume that the car needs to expend more power to warm up if it can't do so rapidly .... you're telling the car to pre-condition the cabin to a temperature it would otherwise never reach in a minute, so it ups the power level? Would make sense to me.

And I don't think there would be any real harm to that beyond normal power expenditures and normal battery degradation - heavy emphasis on "normal". If you want your butt warm in the seat and the cabin warm, more power to you. Pun intended!
 

novox77

1.21 Gigawatts
Nov 25, 2017
2,223
4,719
NH, MA
the good news is that lower temps, the negative effects of degradation from heat is not as severe. I've historically scheduled my charging in the winter to take place around 4am so by the time I head out the door in the morning around 8am, I have enough range and my battery is warm and has full regen available to me.

I do tend to baby my battery, and I'm showing 325mi at 100% charge. Feb 2018 build.
 

SageBrush

REJECT Fascism
May 7, 2015
12,781
17,024
New Mexico
the good news is that lower temps, the negative effects of degradation from heat is not as severe. I've historically scheduled my charging in the winter to take place around 4am so by the time I head out the door in the morning around 8am, I have enough range and my battery is warm and has full regen available to me.
That was my behavior too but now for the winter I charge after the battery is warm from a drive to reduce battery Li plating.
 
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novox77

1.21 Gigawatts
Nov 25, 2017
2,223
4,719
NH, MA
That was my behavior too but now for the winter I charge after the battery is warm from a drive to reduce battery Li plating.

I dropped my draw to 24A to go easier on the battery. Also I have 2 cars to charge so I'm also being mindful of my total draw on my sub panel.
 

DickBlonov

Member
Aug 15, 2019
31
27
Montreal
That was my behavior too but now for the winter I charge after the battery is warm from a drive to reduce battery Li plating.
I would not worry too much about charging when the battery is cold. The only downside is wasted power due to the battery heater bringing the temperature up before charging starts. I also charge after a drive when it's below -10°C.

Phil
 
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mswlogo

Well-Known Member
Aug 27, 2018
6,246
5,378
MA, NH
My theory is the more temperature swings you put the battery through the harder it is on the battery. Now that difference might only change degradation by 0.01% over the normal life of the battery. But I minimize unnecessary temperature swings. I simply never precondition and have range mode normally on.

Also in almost every case it’s less efficient overall to precondition/preheat anything. So it’s win win not to.

I keep my X in range mode (unless headed for a supercharger). Mine is a Model X that has that option which turns off battery heater when Range Mode is on. But Model 3 automatically heats battery on route to supercharger. You can disable Model 3 precondition by putting address of supercharger instead of supercharger itself. Or turn off Nav.

I’m also not sure what is best for battery at supercharger if I don’t care about time. Allow Battery to heat gradually on the way and allow much higher charge currents. Or let supercharger heat it faster (for free in my case) but chances are greater it does not reach peak currents (which might be better for the battery). I do care about this because I SUperCharge fairly often.
 
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WilliamG

Active Member
Apr 20, 2019
4,595
6,480
Seattle, WA
Thanks for your replies but I guess this doesn’t really answer my other question:

How does the car determine whether to use pre-conditioning or not? I wonder if my car was unplugged if it would behave the same way in the colder mornings when I remotely start the heat.

My theory is that if the car is plugged in that when you remotely turn the heat on the car is too cold to take a charge and thus puts itself into pre-conditioning mode. Turning the heat on always causes my HPWC to send a charge to the car. The positive side effect of this is the car heats its batteries up much more quickly.

The downside of this is that it probably isn’t good for the batteries. How not good? Who knows to what extent...

I’m going to guess that’s why it doesn’t always do the pre-conditioning heat when the temperature is warmer, even though it would give me max regen way earlier. It’s able to safely give the car a charge without pre-conditioning so that’s what it does.

I need to test this again with the car unplugged to see if there’s any difference. I’m guessing it won’t do any pre-conditioning when the car is unplugged because the car isn’t charging at that point of course...
 

rdunniii

Member
Jun 27, 2012
265
157
Reno NV
This is why, if departure time charging actually worked, it would be great. If you could set a departure time and start preconditioning before the departure time you could have the battery and the car interior warmed all while still plugged in.
 

jebinc

MSM Model S PLAID, cream/FSD; MYP, white on white
Supporting Member
Jun 19, 2019
7,631
10,773
Seattle area
Other than tricking the car to warming the battery by selecting a SC to navigate to from the app, or using the scheduled predeparture feature in the UI, is there a way to turn on the battery warming/preconditioning from the app say 10 minutes before you head out - so you don't leave with a bunch of regen dots? I understand turning the climate on doesn't do much for preheating the battery as the OP accurately points out.
 
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WilliamG

Active Member
Apr 20, 2019
4,595
6,480
Seattle, WA
Other than tricking the car to warming the battery by selecting a SC to navigate to from the app, or using the scheduled predeparture feature in the UI, is there a way to turn on the battery warming/preconditioning from the app say 10 minutes before you head out - so you don't leave with a bunch of regen dots? I understand turning the climate on doesn't do much for preheating the battery as the OP accurately points out.

I’m guessing the reason this “super-heating” (preconditioning) of the battery doesn’t happen by default in all temperatures is because it’s not good for the battery on a regular basis. That’s just my guess. But it’s dramatic the effect it has on the drivability of the car just 10 minutes later when I get in the car and drive away.
 

jebinc

MSM Model S PLAID, cream/FSD; MYP, white on white
Supporting Member
Jun 19, 2019
7,631
10,773
Seattle area
I’m guessing the reason this “super-heating” (preconditioning) of the battery doesn’t happen by default in all temperatures is because it’s not good for the battery on a regular basis. That’s just my guess. But it’s dramatic the effect it has on the drivability of the car just 10 minutes later when I get in the car and drive away.
Agreed, it takes a really long time to "warm up" to the point where there are no regen dots here in Seattle. I can't imagine what that would be like in Minneapolis in January!
 

WilliamG

Active Member
Apr 20, 2019
4,595
6,480
Seattle, WA
Agreed, it takes a really long time to "warm up" to the point where there are no regen dots here in Seattle. I can't imagine what that would be like in Minneapolis in January!

Not an issue in Minneapolis in January if the car is so cold because the pre-conditioning happens automatically like it’s doing in Seattle right now in the temps we’re having here (30-45F).
 

jebinc

MSM Model S PLAID, cream/FSD; MYP, white on white
Supporting Member
Jun 19, 2019
7,631
10,773
Seattle area
Not an issue in Minneapolis in January if the car is so cold because the pre-conditioning happens automatically like it’s doing in Seattle right now in the temps we’re having here (30-45F).
not mine. My car is in the garage which is about 55°
 

jebinc

MSM Model S PLAID, cream/FSD; MYP, white on white
Supporting Member
Jun 19, 2019
7,631
10,773
Seattle area
Is your car pre-conditioning when you warm it up in a garage at 55F? Mine wasn’t until it dropped to the 40s in my garage.
In this colder weather, I have never left my garage and found no regen dots - so I assume no preconditioning had happened. Could be that my garage is a bit warmer?
 

WilliamG

Active Member
Apr 20, 2019
4,595
6,480
Seattle, WA
In this colder weather, I have never left my garage and found no regen dots - so I assume no preconditioning had happened. Could be that my garage is a bit warmer?

Yes. Exactly. I’ve left my garage which is 45-50F and had no regen limitations after a 15-minute preconditioning which happened automatically when I turned on the heat from the app.
 
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Nocturnal

Well-Known Member
Supporting Member
Aug 23, 2018
6,897
38,834
Deepening Crisis!
Your car won't precondition the battery in your garage, turning on HVAC doesn't do that. Scheduled departure will sort of get you there but it's not the same thing. As far as I know the only intelligent precondition our cars do is if you are navigating to a supercharger.

That aside, I'd say that driving on a warm battery is probably better for it than driving on a cold one, assuming it's warm due to charging. The actual preconditioning (faking an SC route for example) is probably not good for it.
 

WilliamG

Active Member
Apr 20, 2019
4,595
6,480
Seattle, WA
Your car won't precondition the battery in your garage, turning on HVAC doesn't do that. Scheduled departure will sort of get you there but it's not the same thing. As far as I know the only intelligent precondition our cars do is if you are navigating to a supercharger.

That aside, I'd say that driving on a warm battery is probably better for it than driving on a cold one, assuming it's warm due to charging. The actual preconditioning (faking an SC route for example) is probably not good for it.

My car has been preconditioning in the garage, and so has my buddy’s car in Delaware. This started after the latest 2019.40.50.1 which also coincided with colder temperatures for me. That’s with just heating the cabin (not sharing a location to a supercharger or anything).
 

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