Preconditioning for fast charging, worth it?

[davraker]

Over the past couple of winter months, I have driven relatively long distances for skiing. In each case, the car has automatically put itself into the Preconditioning mode as my set navigation was to a Supercharger. While I understand the reasoning behind the preconditioning, I have also noticed that the drain on my battery while in preconditioning transit appears to increase significantly. Thus, my battery is far more drained when I arrive at the supercharger and needs more actual juice.

So my question is, does the increased speed of delivery because of the preconditioning offset the greater amount of electricity needed because of the preconditioning?

Sorry if this has been discussed previously, but I was unable to find this exact question.

thanks for your input.

 

[jjrandorin]

The goal in that instance is faster charging, not saving money. People usually want to spend as little time as possible at a supercharger charging. I have never read any studies on how much money, but yes, heating the battery uses more energy than not heating the battery, so you are likely paying a little more. How much more, and how much time that will save you, I dont know.

If this bothers you, you could always look at the location (address) of the supercharger you are navigating to, then put in an address "close to" it thats not the supercharger. I personally would rather let the car figure out if it needs to pre condition so that I can charge faster vs it costing a bit more.

 

[davraker]

The goal in that instance is faster charging, not saving money. People usually want to spend as little time as possible at a supercharger charging. I have never read any studies on how much money, but yes, heating the battery uses more energy than not heating the battery, so you are likely paying a little more. How much more, and how much time that will save you, I dont know.

If this bothers you, you could always look at the location (address) of the supercharger you are navigating to, then put in an address "close to" it thats not the supercharger. I personally would rather let the car figure out if it needs to pre condition so that I can charge faster vs it costing a bit more.

Thanks for your reply.

It’s not the cost actually that I’m thinking about, though it is a factor.

I recognize that the battery will be able to power faster, but if it needs to power more because my battery is lower because of the preconditionin, then does it, in the end, save me time?

 

[Woggon]

I would say it depends on temperature. My experience is it turns on a long ways away in very cold temperatures and burns a lot of battery as it cycles on and off trying to keep the battery at the desired temp. If it’s sub zero I’d suggest setting someplace close to the supercharger as your destination until you are maybe 20 miles out, otherwise you lose a lot of charge as the pre-condition cycles on and off.

Just remember to pre condition or you’ll be charging at something like 40 kW or less, and that is not fun.

 

[Langzaiguy]

I've noticed when it preconditions early (maybe an hour before reaching the charger), the car isn't using any additional energy. It's just pushing waste heat to the battery. When you get somewhat closer and it still needs to precondition, it may heat it actively by running the motors inefficiently--up to 7kW I believe. If it does that for half an hour, it might burn through 5% if my math is right. So if you're able to charge the car at 250kW rather than 70kw (or whatever), you're going to get those 3-4kWh that you spent heating the battery back pretty quickly.

 

[mswlogo]

I've noticed when it preconditions early (maybe an hour before reaching the charger), the car isn't using any additional energy. It's just pushing waste heat to the battery. When you get somewhat closer and it still needs to precondition, it may heat it actively by running the motors inefficiently--up to 7kW I believe. If it does that for half an hour, it might burn through 5% if my math is right. So if you're able to charge the car at 250kW rather than 70kw (or whatever), you're going to get those 3-4kWh that you spent heating the battery back pretty quickly.

If you are an hour away it doesn't do anything initially in my experience. And if you are that far away it probably doesn't need to precondition for faster charging that much any way. Battery will naturally warm.

I deliberately never use it (added separate Saved GPS locations for landmarks near Super Chargers). Since all it does is waste energy.

I also prefer not charge my battery at 250kw. 125kw-ish is just fine by me.

 

[Woggon]

If you are an hour away it doesn't do anything initially in my experience. And if you are that far away it probably doesn't need to precondition for faster charging that much any way. Battery will naturally warm.

I deliberately never use it (added separate Saved GPS locations for landmarks near Super Chargers). Since all it does is waste energy.

I also prefer not charge my battery at 250kw. 125kw-ish is just fine by me.

It depends on temperature. In sub zero to -30F weather I’ve seen it start pre-conditioning at 120 miles out and drain the battery very fast. At -30F with pre conditioning the range isn’t much more than 120 miles on a Model Y Long Range with the heat on defrosting so you can see out the windows.

 

[KzooMYP]

Yes.

Preconditioning, as I understand it, heats or cools the battery for optimum charging throughput. Charger performance aside; thermals are supposed to be one of the biggest factors in charge speed.

Kyle from Our of Spec reviews is doing deep dives on the R1T and it's charging performance. Its charging performance leaves a lot to be desired, and Kyle mentions one of the reasons is the lack of battery preconditioning features.

I wouldn't have expected it to matter so much; but preconditioning to matter so much, but Kyle does a great job explaining it.

 

[FatherTo1]

Are Superchargers themselves affected by deep freeze? Let’s say you precondition the battery, if the Supercharger hasn’t been used in a while and it’s below zero outside, will it still be able to deliver peak charge rates?

 

[Big Earl]

Are Superchargers themselves affected by deep freeze? Let’s say you precondition the battery, if the Supercharger hasn’t been used in a while and it’s below zero outside, will it still be able to deliver peak charge rates?

In my experience, they are not affected by cold. Extreme heat can slow down V2 superchargers but has minimal effect on V3 superchargers.

 

[Woggon]

Are Superchargers themselves affected by deep freeze? Let’s say you precondition the battery, if the Supercharger hasn’t been used in a while and it’s below zero outside, will it still be able to deliver peak charge rates?

I don’t believe they are, similarly transformers typically aren’t affected by normal ambient operating temperatures. Once you hit 50 C you may see some efficiency losses, but generally transformers are probably more efficient at lower temperatures until somewhere close to -40c/f, then temperature inflicted contraction can cause some funny things to happen. A supercharger is really just a transformer - going from high voltage to medium or low voltage (from a power transmission standpoint).

 

[ZenRockGarden]

As best I can tell - it's simply about optimizing charging speed (with thermal pre-prep). This uses quite a bit of power from the battery so if max-efficiency is the goal maybe preconditioning isn't the right move.

 

[mswlogo]

It depends on temperature. In sub zero to -30F weather I’ve seen it start pre-conditioning at 120 miles out and drain the battery very fast. At -30F with pre conditioning the range isn’t much more than 120 miles on a Model Y Long Range with the heat on defrosting so you can see out the windows.

Luckily I have no experience with -30F

 

[MY-Y]

From my experience, preconditioning burns a ton of power starting a full hour from the supercharger when the temp is below freezing. It also makes a high pitch whine. I wish there was a way to start preconditioning the battery, say 10 minutes before a charger. The battery won't hit 120 degrees for max speed, but it won't be super slow either.

 

[SageBrush]

So my question is, does the increased speed of delivery because of the preconditioning offset the greater amount of electricity needed because of the preconditioning?

Big time

 

[mswlogo]

Big time

Maybe in time, but not in cost.

 

[SageBrush]

I've noticed when it preconditions early (maybe an hour before reaching the charger), the car isn't using any additional energy. It's just pushing waste heat to the battery. When you get somewhat closer and it still needs to precondition, it may heat it actively by running the motors inefficiently--up to 7kW I believe. If it does that for half an hour, it might burn through 5% if my math is right. So if you're able to charge the car at 250kW rather than 70kw (or whatever), you're going to get those 3-4kWh that you spent heating the battery back pretty quickly.

Continuing this line ...

7 kW for 30 minutes is 3.5 kWh
If the supercharger doubles its power, say from 75 to 150 kW due to to the warmer battery, the pre-conditioning is recouped in 2.8 minutes

Moreover, If I'm not mistaken, if a car pulls into a Supercharger with a cold battery and charges, the car will spin its motors during charging to heat up the battery -- exactly the same as what happens during pre-conditioning. So this is not a case of a trade-off -- the battery heating mostly happens either way by wasting motor energy. The substantial difference is that the battery heating is time shifted.

 

[MY-Y]

It cuts your range way, way down. An extra 100+ Wh/mi makes a big difference.

 

[mswlogo]

Continuing this line ...

7 kW for 30 minutes is 3.5 kWh
If the supercharger doubles its power, say from 75 to 150 kW due to to the warmer battery, the pre-conditioning is recouped in 2.8 minutes

Moreover, If I'm not mistaken, if a car pulls into a Supercharger with a cold battery and charges, the car will spin its motors during charging to heat up the battery -- exactly the same as what happens during pre-conditioning. So this is not a case of a trade-off -- the battery heating mostly happens either way by wasting energy. The substantial difference is that the battery heating is time shifted.

Good point

I think it partly depends exactly at what temps you are at.

I think there are temps that it won’t take steps to heat the battery and just go slow (like 75kw). And there are temps where it almost has to heat the battery some to get minimal charging speed (like well below 50kw).

 

[SageBrush]

Maybe in time, but not in cost.

Definitely in time, and the cost is not much different.
For pre-conditioning it is all motor spinning; during charging it is a combination of motor spinning and resistance losses in the battery. I'm not positive about this ... but I somewhat recollect that resistance losses are ~ 5%. If true and your cold battery charging is 50 kW then the resistance losses are in the 2.5 kW range while motor losses from adding heat are in the 7 kW range. You save about 20% of 3.5 kWh of costs. Call it 0.5 - 1.0 kWh

As for battery health, that is an interesting question that only Tesla knows the answer. During DC charging the main problem is Li plating, itself proportional to power and inversely proportional to battery temperature.