Did you know the 3 heats the battery (actively) constantly while DC charging at any speed or temp?

[SouthSeas]

BTW, to clarify the principle I would like to note the following (I'm a masters student electrical engineering, so I understand more and more of physics principles, but also I make mistakes, so please correct me if I'm wrong). In normal language: higher temperatures make it easier for ions to move (higher mobility). Part of the degradation is the fact that the ions are 'pushed' through the resistance. That is also why ludricous mode heats the battery, since that makes it easier to extract electrons from the battery (so less voltage drop and less degradation because of use). On the other hands, the high temperature accelerates chemical degradation processes (dendrite forming, etc), but apparently the one effect outweighs the other.

I don't think you are going to find anyone here with enough battery knowledge to support or refute your statements.

What I can tell you is that lithium plating is a major cause of wear on the batteries. That is why these batteries can not be charged at low temperatures, the plating becomes extreme. It may well be that at higher temperatures lithium plating becomes virtually non-existent increasing the life of the battery, but I don't know that for sure. I would have thought this would have been known some time ago and all EVs would keep the battery not just above freezing, but hot during charging. 60°C is 140°F which is hot enough to burn you.

I will also say that heating the battery pack to 140°F each time it is charged is a large expense and waste of energy (waste in the sense of it doesn't propel the car). If they are using more than half the available charging power to heat the battery while slow charging that make the EV even less efficient than an ICE!

 

[SageBrush]

basically it never happens for AC charging, but it happens pretty much constantly with DC charging), but AC charging is not fundamentally different from DC charging

5 - 10 kW charging AC
Up to 250 kW DC

Can you spot the difference ?

 

[SouthSeas]

Yeah, I'll add everything I said in OP that's been ignored. Particularly, that it doesn't help speed charging in most cases. If you're waving around this "Li plating" theory as the only defense for this unconditional heating behavior, you're standing on pretty shaky ground given that it doesn't do this with AC charging (it gets the battery above freezing, and that's it - basically it never happens for AC charging, but it happens pretty much constantly with DC charging), but AC charging is not fundamentally different from DC charging.

Yes, they are fundamentally different in that AC charging is much slower than DC charging and lithium plating is directly related to charging speed. So while DC charging may cause small, but significant lithium plating, AC charging likely causes virtually none. You don't need to mitigate an effect if it isn't happening.

I still fail to understand where the wild responses of defense are coming from. This is incredibly wasteful behavior that just puts a tax on your energy bill and slows down charging. It's bad from every angle except the highest speed Supercharging. Bjorn's video worked from "see symptom" to "try to explain cause", while I'm working from "see symptom" to "try to explain how to make it better".

There needs to be more logic to prevent this heating when it's not necessary or helpful. My theory is that this is still just something that was programmed and forgotten, left unrefined after it worked once. There's significant room for improvement -- like not heating the battery if the station reports under a certain power, or if you've selected a lower charging limit.

Yeah, it would be good to turn this off when not helpful, but we don't have any way of knowing what is helpful and what isn't. Your OP talks about Tesla "forgetting" to deal with this... I seriously doubt Tesla "forgot" anything having to do with battery life. The only question is whether or not it is the best way to deal with battery life vs. use of energy.

In 10 years I will put $40,000 worth of electricity into my ~$20,000 battery. It will take a lot of waste to make it not worthwhile to extend the life of the battery.

 

[camalaio]

I can corroborate these findings with my own: Time Remaining vs. kW rate

tl;dr - I was at a temporary CHAdeMO station which delivers 10kW to other vehicles. Model 3 only gets 5kW.

I thought 4-6kW was going to cooling, but your findings and Bjorn's show that it's actually heating.

Ridiculous because it doesn't do this for a 10kW J1772 charging station, only for DC. I agree the logic is likely as simple as "if DC charging, make heat". It was wasteful and actually made the Level 2 chargers the faster option in a remote area.

 

[SageBrush]

I will also say that heating the battery pack to 140°F each time it is charged is a large expense and waste of energy (waste in the sense of it doesn't propel the car). If they are using more than half the available charging power to heat the battery while slow charging that make the EV even less efficient than an ICE!

Bjorn measured the energy spent to pre-heat the battery on the way to a Supercharger. It is modest

 

[SouthSeas]

Bjorn measured the energy spent to pre-heat the battery on the way to a Supercharger. It is modest

"Modest"... sounds like 1, 2, 3, many. How much is "modest"?

 

[justsomeguy]

"Modest"... sounds like 1, 2, 3, many. How much is "modest"?

In an AWD vehicle I believe the max energy the car puts out is 4kW for battery heating while in drive. 7.5kW while parked.

 

[SageBrush]

I agree the logic is likely as simple as "if DC charging, make heat". It was wasteful and actually made the Level 2 chargers the faster option in a remote area.

If I recall correctly, the DC charger does not include its specs in the handshake.

 

[SageBrush]

"Modest"... sounds like 1, 2, 3, many. How much is "modest"?

That would vary by the starting battery temperature. My memory of the video is fuzzy but I think (no promises) that it was something over a kWh to heat 20C. Bjorn said something like "not too bad" and I was thinking the same.

Again from my fuzzy memory, battery cells are ~ 200 mOhm. Once the pack is warm enough to support 50 - 100 kW charging the resistance heat is a strong helping hand.

 

[SouthSeas]

In an AWD vehicle I believe the max energy the car puts out is 4kW for battery heating while in drive. 7.5kW while parked.

My car is the X, the most inefficient in the Tesla lineup and it averages ~20 kW on trips. 4 kW on top of that (+20%) is not what I call "modest". That would push my consumption from 333 Wh/mi to 400 Wh/mi and my range from 285 down to 237 miles. I guess it's not on the whole trip, but I still would not call that "modest".

In an ICE if your range dropped even 10% you would start looking for a cause. In a Tesla this can make the difference in skipping a charger and reaching the next one or having to charge twice rather than just once.

I believe this preheating is about minimizing the time at the charger. When looking at the time saved, do they consider the time it takes to charge the lost heating energy?

 

[justsomeguy]

My car is the X, the most inefficient in the Tesla lineup and it averages ~20 kW on trips. 4 kW on top of that (+20%) is not what I call "modest". That would push my consumption from 333 Wh/mi to 400 Wh/mi and my range from 285 down to 237 miles. I guess it's not on the whole trip, but I still would not call that "modest".

In an ICE if your range dropped even 10% you would start looking for a cause. In a Tesla this can make the difference in skipping a charger and reaching the next one or having to charge twice rather than just once.

I believe this preheating is about minimizing the time at the charger. When looking at the time saved, do they consider the time it takes to charge the lost heating energy?

When you're talking about a cold battery, you absolutely save a lot of time. 4kW for ~15 minutes isn't that bad when your entire goal is to minimize downtime at the supercharger.

Of course you can just not navigate to it, but apparently the car will expend that energy while plugged in anyway. 4kW at ~15 minutes is 1kWh and will be under an extra minute to charge, or if you significantly increase your charge rate is almost nothing to recover.

 

[justsomeguy]

This 4kW number is for AWD Model 3s. The pre raven (maybe even the raven?) X and S have dedicated 6kW pack heaters so I'm assuming you'll be running at that power.

 

[derotam]

In an AWD vehicle I believe the max energy the car puts out is 4kW for battery heating while in drive. 7.5kW while parked.

Close...but technicality... In DRIVE, it can be up to the ~7.5kW since stopped can still be in drive. While in motion, since the front motor is not used very much in normal conditions it will still be using ~3.5kW, but the rear motor will be variable. I have seen heating power being sent to the motor at slow speeds but it goes away the faster you go. I think it is gone by the time you get up past ~10mph or so. I have been trying to figure out a way to get that curve plotted but have been unable to thus far.

 

[bedoig]

Guy witnesses battery heat up when cold. Assumes it must mean it heats up when hot too. Lol.

As others have said, it heats to its target then will cool as necessary. Try again in warm weather and be amazed!

 

[justsomeguy]

Guy witnesses battery heat up when cold. Assumes it must mean it heats up when hot too. Lol.

As others have said, it heats to its target then will cool as necessary. Try again in warm weather and be amazed!

I don't doubt that this guy is right, as a matter of fact I fully believe that the car will heat indiscriminately until it reaches some set point that's likely hard coded. I'm guessing it's the temperature at which the car can achieve max L3 charge rate (whatever it takes to hit the V3 supercharger curve). There's not really any issue in this when you're hitting an L3 supercharger and are intending to hit a high SoC, but if you're plugging in to a 50kW CHAdeMO and your car is capable of >50kW and you only need +10%SoC, it is absolutely just a waste of time to run the battery heating.

My only criticism was the weird safeguarding of his rather publicly known method.

 

[bedoig]

@Rocky_H Care to elaborate on the disagree? I've also monitored via CAN, and while there is a pretty high temp target, it definitely actively heats to a certain point then cools to maintain that target. It's not exactly unexpected behavior. The car literally tells you about it when you navigate to a supercharger. To @justsomeguy's point, it may be somewhat unnecessary in some circumstances, but the title and premise of the entire thread is demonstrably false.

 

[camalaio]

@Rocky_H Care to elaborate on the disagree? I've also monitored via CAN, and while there is a pretty high temp target, it definitely actively heats to a certain point then cools to maintain that target. It's not exactly unexpected behavior. The car literally tells you about it when you navigate to a supercharger. To @justsomeguy's point, it may be somewhat unnecessary in some circumstances, but the title and premise of the entire thread is demonstrably false.

Not the person you're asking, but...

Your statement expressed a couple dubious points.

They did not assume it would heat when hot. They stated heating even over 110F (which is fairly warm, if not "hot"). Also, with using just the battery heating alone (e.g. slow L3 station not contributing much by heat losses), it takes a long time to raise the battery's temperature. In my case above, I had sat at that charging station for well over an hour while it was 10C outside (sort of cold). The fans never ramped up after or during charging, implying cooling wasn't employed at all. Heating for over an hour.

Your point about trying in warm weather - I've seen it preheat on the way to a Supercharger on a rather hot day even after driving around for a while. Many people have seen this. One will not "be amazed" at anything but the revelation that it does indeed heat even in hot outside temperatures, exactly what the OP pointed out.

 

[bedoig]

@camalaio Ok, you didn't actually dispute anything I said, so I guess we're in agreement. I said it heats until it hits its target then cools, which it does. Luckily the car is using actual temperature measurements and targets rather than relying on your assessment of whether it's "fairly warm," "sort of cold," or "rather hot."

 

[camalaio]

@camalaio Ok, you didn't actually dispute anything I said, so I guess we're in agreement. I said it heats until it hits its target then cools, which it does. Luckily the car is using actual temperature measurements and targets rather than relying on your assessment of whether it's "fairly warm," "sort of cold," or "rather hot."

We agree that it has these temperature points, yes. We do not agree that the "premise of the entire thread is demonstrably false".

The car heats when it doesn't need to and is wasteful (again, for the extreme example, look at my 10kW CHAdeMO scenario). This is the bulk of the discussion in the original post. Catching the technicality of the title implying it only ever heats isn't productive; we all know it reaches some top temp that's relatively high, and thus it does actually apply quite a lot of intentional heating especially at lower charge rates. The point is that this heating is not always required or beneficial. It serves to provide faster charging, which you simply won't get at a 50kW CHAdeMO station and perhaps not even at an Urban Supercharger capped to 70kW. At that point it is indeed just wasted energy.

At freezing temps without a pre-warmed battery, I plugged into a v2 Supercharger at about 30% state of charge and got a maximum of 79kW. A warm battery would have made this faster, yes. But it also was happy to pull 79kW with a cold battery, implying heating is not necessary (at least not as much) for lower charge rates (e.g. CHAdeMO or Urban Superchargers).

 

[bedoig]

I agreed with the fact it could be unnecessary in some scenarios. I just don't see what the point of this discussion is because we've all known about the battery conditioning since it came out. It was in the release notes and the car tells you about it on-screen. No CAN sniffing needed. The thread title wasn't a small technicality. It made it very clear using plenty of words that the car was doing something incredibly stupid, which it doesn't do.

Oh well, you can carry on without me. I'd say Happy Thanksgiving, but I see you're in Canada, so I'll just say enjoy the rest of your week