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I want to make a small correction that Tesla themselves will tell you (though they have a hard time saying it directly).

Having the battery this hot is not good for it's health. 60C is not "just fine". It's a trade-off Tesla has deemed acceptable to achieve faster charge rates, which is not the same thing as being good for the battery. I'm highlighting the difference between "normal" and "beneficial".

Charging at high such high temperatures (especially when not useful, e.g. how it works for CHAdeMO/CCD stalls <=50kW) does bad things to your battery longevity. Nearly every other manufacturer (EVs, phones, tool batteries, etc.) prevents you from charging at high temperatures. This very likely isn't because Tesla's chemistry is better or unique, just that they're accepting a risk for a different gain.

Understood but when you factor that into the lifespan of a car and how many times it is charged / discharged faster is it really anything to worry about say over 8 or 10 years?
 
The Chademo heating drives me nuts. The adapter only supports 50kW and it's alwasy dumping 7kW to heat the battery even on a 100Amp chademo.
It doesn't *always* do it. I think it might only do this extra heating when you charge to high SoC levels. The data below is from another charge session, with SoC ~60%. There is ~45kW going into the battery, and the battery inlet temperature is slightly lower than the battery temperature (~26°C).
warm-battery.png
 
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Almost every time i've charged on chademo the output of the charger and what's going into the battery are about 8kW off and I can hear the whine of the motor heating. Good to know there are some times it's intelligent about it though.
 
Understood but when you factor that into the lifespan of a car and how many times it is charged / discharged faster is it really anything to worry about say over 8 or 10 years?

Actually, yes. While many will say it's "fine" to use Supercharging exclusively, it's clear that it's detrimental to both the service life and battery performance. Tesla will start limiting your charge rates after certain conditions are reached. This is implied to be based on measurements of the battery (probably some combo of estimated cell capacities, estimated internal resistance, perhaps thermal cycle events, etc.). I have no reason to believe this isn't true, but something as simple as "number of times at a Supercharger" doesn't seem to be the case either.

Time is a difficult measure simply because some people do 50,000mi in 8 years, and people like me do closer to 400,000mi. The takeaway should be that if your battery is routinely exposed to high heat, its lifetime will suffer. Of course in the case of Supercharging, that's also coupled with high charge rates so the Tesla-specific data is a bit muddled. But this is pretty well understood for Li-ion chemistry in general, and the cells Tesla uses are not currently an exception to that understanding.

If you want to get the 500,000mi lifetime Elon expects for a Model 3 battery, you cannot:
  • DC Fast Charge often
  • Use Sentry a lot, or use Summon Standby (these use power without adding miles)
  • Live in a battery-unfriendly environment (very cold, very hot)

It doesn't *always* do it. I think it might only do this extra heating when you charge to high SoC levels. The data below is from another charge session, with SoC ~60%. There is ~45kW going into the battery, and the battery inlet temperature is slightly lower than the battery temperature (~26°C).View attachment 560652

Huh. Perplexing. I've always had it heat - low SoC, high SoC. Certainly above 26C as you have there. I can't think of what other variable would be involved though. This is a Model 3 datapoint, right?
 
camalaio - thanks for the details you wrote up in this thread. I've been looking for the in-depth summary like this for a long time. I agree with everything you wrote.

Two items that stood out include:

1. Model Y's heat pump and connection to the battery pack could really improve winter comfort. If you've got a warm battery pack, there's a lot more to draw from. The question is going to be... let's say it's 20F outside and you're plugged in, charging to 100% for a road trip. How warm will the car get the battery for this effect? If charging finishes within an hour of your departure, will the 1,000 pound battery pack have enough warmth for this? Will it engage the heat pump during warm up to heat the battery pack even if you're not charging?

2. Supercharger speeds are designed for convenience and also likely supercharger turnover. Faster charging does make things more convenient for those short on time, but we know it contributes to higher degradation. The other benefit is that during busy holiday seasons, it allows them to handle more cars than they could otherwise service at the supercharger.

I'm curious to see if the Model Y is able to precondition the battery better than the existing cars without a heat pump. This could obviously be good before you arrive to a supercharger, but also good when you charge at home so the battery can be warm and serve as a source of heat over your road trip.

The implications of the heat pump and use of the battery pack are large and I can only wonder why Tesla didn't build these in sooner. Maybe they did and ran into limitations we aren't aware of yet. As someone who does a lot of road trips, performance in weather down to 20F is important and I'm hopeful to see data that shows added comfort in the cabin and range from the heat pump. I wonder if we'll see any data before the winter or if we really have to wait till January/February.
 
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camalaio - thanks for the details you wrote up in this thread. I've been looking for the in-depth summary like this for a long time. I agree with everything you wrote.

Two items that stood out include:

1. Model Y's heat pump and connection to the battery pack could really improve winter comfort. If you've got a warm battery pack, there's a lot more to draw from. The question is going to be... let's say it's 20F outside and you're plugged in, charging to 100% for a road trip. How warm will the car get the battery for this effect? If charging finishes within an hour of your departure, will the 1,000 pound battery pack have enough warmth for this?

2. Supercharger speeds are designed for convenience and also likely supercharger turnover. Faster charging does make things more convenient for those short on time, but we know it contributes to higher degradation. The other benefit is that during busy holiday seasons, it allows them to handle more cars than they could otherwise service at the supercharger.

I'm curious to see if the Model Y is able to precondition the battery better than the existing cars without a heat pump. This could obviously be good before you arrive to a supercharger, but also good when you charge at home so the battery can be warm and serve as a source of heat over your road trip.

The implications of the heat pump and use of the battery pack are large and I can only wonder why Tesla didn't build these in sooner. Maybe they did and ran into limitations we aren't aware of yet. As someone who does a lot of road trips, performance in weather down to 20F is important and I'm hopeful to see data that shows added comfort in the cabin and range from the heat pump. I wonder if we'll see any data before the winter or if we really have to wait till January/February.

I'm not familiar with what amount of heat could be extracted from the battery, but the heat in the battery at 100% will vary. Fresh off a DC Fast Charger, it'll be above 40C (104F). But if it was Level 2 charging, there's a lot of variables. In Winter, I wouldn't expect it to be warmer than room temp. Probably about 15C (59F). That's not a lot of room for extracting heat for the cabin. That said, if it was charged for a long time at high power in a somewhat insulated space, maybe it gets up to 25C or so? If this is your case with a Model Y, I expect Winter efficiency would be relatively excellent.

The battery will have much of this heat still an hour later (it won't purposely dump it). Of course, it would lose it faster outside though.

People are going to have very mixed results with the heat pump because of the above, but it should be better overall. I suspect Tesla didn't do it sooner due to complexity. There's many things simultaneously needing heat or cooling (cabin, battery, drive units) within temperature parameters (efficiency, not sucking too much heat from the pack, etc. Also, AC compressors die often, and this now makes it run effectively all year.
 
I'm not familiar with what amount of heat could be extracted from the battery, but the heat in the battery at 100% will vary. Fresh off a DC Fast Charger, it'll be above 40C (104F). But if it was Level 2 charging, there's a lot of variables. In Winter, I wouldn't expect it to be warmer than room temp. Probably about 15C (59F). That's not a lot of room for extracting heat for the cabin. That said, if it was charged for a long time at high power in a somewhat insulated space, maybe it gets up to 25C or so? If this is your case with a Model Y, I expect Winter efficiency would be relatively excellent.

The battery will have much of this heat still an hour later (it won't purposely dump it). Of course, it would lose it faster outside though.

People are going to have very mixed results with the heat pump because of the above, but it should be better overall. I suspect Tesla didn't do it sooner due to complexity. There's many things simultaneously needing heat or cooling (cabin, battery, drive units) within temperature parameters (efficiency, not sucking too much heat from the pack, etc. Also, AC compressors die often, and this now makes it run effectively all year.
I see what you're saying. Do you think they would allow dumping heat into the battery pack intentionally as part of the warmup? Maybe it's something that is enabled while on range mode and charging? I see the benefit ahead of a road trip, but maybe I'm underestimating just how much power and time it would take. The simplest is likely still to just have the battery pack finish charging shortly before departure (level 2, home charger).
 
I see what you're saying. Do you think they would allow dumping heat into the battery pack intentionally as part of the warmup? Maybe it's something that is enabled while on range mode and charging? I see the benefit ahead of a road trip, but maybe I'm underestimating just how much power and time it would take. The simplest is likely still to just have the battery pack finish charging shortly before departure (level 2, home charger).

It does indeed take a lot of energy to change the battery temperature. They do it automatically if you precondition the cabin and the battery is cold (partly why I think they recommend something ridiculous like preconditioning for at least 30 minutes) at any state of charge and whether or not it is plugged in.

Otherwise I don't see them purposely exposing something so technical as a user control for heating the battery. Removes the illusion that Tesla universally does the right thing all the time, as well as adds yet another feature they have to test and maintain.
 
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It does indeed take a lot of energy to change the battery temperature. They do it automatically if you precondition the cabin and the battery is cold (partly why I think they recommend something ridiculous like preconditioning for at least 30 minutes) at any state of charge and whether or not it is plugged in.

Otherwise I don't see them purposely exposing something so technical as a user control for heating the battery. Removes the illusion that Tesla universally does the right thing all the time, as well as adds yet another feature they have to test and maintain.
Makes sense. Hopefully they release the heat pump for the model 3 - I can make it work for my long drives with its HVAC improvements. There might be a benefit from drawing the battery pack's heat during the winter and that would also help.
 
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It does indeed take a lot of energy to change the battery temperature. They do it automatically if you precondition the cabin and the battery is cold (partly why I think they recommend something ridiculous like preconditioning for at least 30 minutes) at any state of charge and whether or not it is plugged in.

Otherwise I don't see them purposely exposing something so technical as a user control for heating the battery. Removes the illusion that Tesla universally does the right thing all the time, as well as adds yet another feature they have to test and maintain.
In a recent video, Tesla Bjorn provides some evidence that Tesla is using the battery pack as a "store of heat."

Go to the 8 minute mark of this video to see it yourself: #69 Road trip to Stavanger in 2021 Model 3

Bjorn says the car scavenges battery pack heat for the cabin. He notices it draw down to 15-18C in cold weather (0C or even lower). When it warms outside, like +5C, it adds heat to the battery pack rising in his video to 25C.

This is a first step, in my opinion, to a major improvement for winter comfort in an EV. Theoretically, if you are plugged in and finish charging before you leave, Tesla can warm the battery pack pretty well and provide heat for your trip in fairly cold conditions extending range and increasing comfort (heat) without draining the battery too much. There are going to be limits to its capability (such as even colder temperatures), but this improvement is already significantly better than a model from 5 years prior. The key is to start with a full/warm battery pack, which most people with an EV can do because they charge at home.
 
In a recent video, Tesla Bjorn provides some evidence that Tesla is using the battery pack as a "store of heat."

Go to the 8 minute mark of this video to see it yourself: #69 Road trip to Stavanger in 2021 Model 3

Bjorn says the car scavenges battery pack heat for the cabin. He notices it draw down to 15-18C in cold weather (0C or even lower). When it warms outside, like +5C, it adds heat to the battery pack rising in his video to 25C.

This is a first step, in my opinion, to a major improvement for winter comfort in an EV. Theoretically, if you are plugged in and finish charging before you leave, Tesla can warm the battery pack pretty well and provide heat for your trip in fairly cold conditions extending range and increasing comfort (heat) without draining the battery too much. There are going to be limits to its capability (such as even colder temperatures), but this improvement is already significantly better than a model from 5 years prior. The key is to start with a full/warm battery pack, which most people with an EV can do because they charge at home.

(warning: contrarian opinion ahead)

I'm not sure if I agree with his assessment of what's happening, though I did notice some interesting behaviours later in the video. I'll explain with what my 2019 Model 3 LR AWD does. This is the first data I've seen from a heat pump Tesla, so I have a big thought dump!

On a long trip (which he was clearly on), the waste heat from the motors being dumped into the battery will maintain about a 24C difference compared to ambient (assuming no other measures are taken, like cooling via the radiator or applying heat via the motors). So for example, when it's 5C outside on a long drive, I expect to see about 29C on the batteries. If I just came off a Supercharger and the pack is closer to 60C, I expect it to drop down to about 29C eventually as well in those same conditions. This isn't my car using the battery as a "store" of heat though - it's just keeping the motors cool and the battery warm. In both summer and winter I'd say the average "passive target" temp for the battery seems to be about 35C.

So I find it interesting Tesla is happy to run the batteries much cooler now, 15-18C as Bjorn mentioned, just to suck some heat from the system. There is noticeably less extractable energy at this temp (about 1%) and more regen limitation (will vary based on SoC, but could be very significant at higher SoC). The colder battery will also tend to imbalance itself under discharge easier.

Now, regarding the points in his video:
  • Sitting at 24C with 5C outside, it's clear to me that some heat was probably drawn out of the battery, yes. Cool.
  • It's unclear if the battery is actively heated (motors intentionally generating heat) or passively heated (just normal waste heat from driving the motors) to that 25C point before it draws heat out, down to 15-18C. Both are possible in that 5C outdoor temp based on what I've observed in my 2019 model. It would be noticeable with the cycle time on this behaviour - longer likely means passive, which is likely also more efficient (depending how it generates heat when not scavenging from the pack).
  • He's guessing it's not using the battery as a heat source at that 8 minute mark, and is "saving it for later". It lacks the data and forecasting to make that bet - I think it's more likely that it's using the air like he mentioned but temporarily, as it likely cycles between a few different modes. He was also parked, which could change its behaviour (since it can't expect passive waste heat is coming from the motors anymore, unless it actively does so). To me, this is indication that it is probably depending on passive waste heat in the point above.
  • Unless I interpreted it wrong, he seemed to claim that previous Model 3s didn't precondition to around 25C at low SoC for Supercharging. That's absolutely and demonstrably false with my own Model 3. I'm guessing he just didn't have an equivalent scenario, or that his battery was already warm enough from driving and he simply didn't make a note of it (highly likely). Before heat pumps, it was easier to still have leftover heat from the previous Supercharger session, so preconditioning is less likely on long trips like he does. However with the heat pump system drawing it down to 15C, it will need to actively heat for more Supercharging sessions than the older models. Yes, that does mean the 2021 model has a scenario where it's using more power than the older models. Weird eh? It might balance out.
  • He didn't mention it, but his overnight sleep it was clearly using the motors as a n actively powered heat source while parked (they're above 40C while everything else is cold, including the battery). This is strange - it would be less efficient than a PTC element like on the older Model 3s. I guessed this would be the case around and below freezing temps (it was at freezing at that point in the video), but this isn't how I thought it would work. Interesting. It's also possible that it was using this heat for something else (e.g. the battery).
I kind of wonder what a freezing cold 2021 Model 3 will do. My 2019 will actively heat the pack to about 0C, then just with waste heat from the motors after that (which takes a long time). I already think this is a massive waste of energy for short hops - I drive 4km/day right now, using 30-50km of range to do so (a large chunk of which is actively heating the darn battery just to 0C). I really, really hope the 2021 ones do not try to actively heat the pack to 15+C on similar trips just to use as a heat source - that would be a gargantuan waste of energy for short commutes.

It's worth mentioning that I disagree with a lot of Bjorn's observations, so I have a bias already. He has a large following and has made some very false suggestions/observations (not claims) regarding Model 3 - nothing super detrimental, but mildly annoying given his very large following that takes his word on most things.

His takeaway that the trip meter says 172Wh/km so it's done better than the previous models is seriously flawed. The trip meter does not count usage while parked. I don't doubt that it is more efficient in mild winter temps (which it seemed like he was in - heavy snow, wet roads, 0C when he woke up near noon) and especially on long trips with lots of DC fast charging (which dumps tons of heat in the battery to scavenge). Basically, this trip of his was the best case scenario for the heat pump system. I'd put a huge "To Be Determined" label on how it compares in daily commuter scenarios in colder temperatures.

And this concludes my wall of text / thought dump. Excited to see more data with the heat pump behaviour!
 
(warning: contrarian opinion ahead)

I'm not sure if I agree with his assessment of what's happening, though I did notice some interesting behaviours later in the video. I'll explain with what my 2019 Model 3 LR AWD does. This is the first data I've seen from a heat pump Tesla, so I have a big thought dump!

On a long trip (which he was clearly on), the waste heat from the motors being dumped into the battery will maintain about a 24C difference compared to ambient (assuming no other measures are taken, like cooling via the radiator or applying heat via the motors). So for example, when it's 5C outside on a long drive, I expect to see about 29C on the batteries. If I just came off a Supercharger and the pack is closer to 60C, I expect it to drop down to about 29C eventually as well in those same conditions. This isn't my car using the battery as a "store" of heat though - it's just keeping the motors cool and the battery warm. In both summer and winter I'd say the average "passive target" temp for the battery seems to be about 35C.

So I find it interesting Tesla is happy to run the batteries much cooler now, 15-18C as Bjorn mentioned, just to suck some heat from the system. There is noticeably less extractable energy at this temp (about 1%) and more regen limitation (will vary based on SoC, but could be very significant at higher SoC). The colder battery will also tend to imbalance itself under discharge easier.

Now, regarding the points in his video:
  • Sitting at 24C with 5C outside, it's clear to me that some heat was probably drawn out of the battery, yes. Cool.
  • It's unclear if the battery is actively heated (motors intentionally generating heat) or passively heated (just normal waste heat from driving the motors) to that 25C point before it draws heat out, down to 15-18C. Both are possible in that 5C outdoor temp based on what I've observed in my 2019 model. It would be noticeable with the cycle time on this behaviour - longer likely means passive, which is likely also more efficient (depending how it generates heat when not scavenging from the pack).
  • He's guessing it's not using the battery as a heat source at that 8 minute mark, and is "saving it for later". It lacks the data and forecasting to make that bet - I think it's more likely that it's using the air like he mentioned but temporarily, as it likely cycles between a few different modes. He was also parked, which could change its behaviour (since it can't expect passive waste heat is coming from the motors anymore, unless it actively does so). To me, this is indication that it is probably depending on passive waste heat in the point above.
  • Unless I interpreted it wrong, he seemed to claim that previous Model 3s didn't precondition to around 25C at low SoC for Supercharging. That's absolutely and demonstrably false with my own Model 3. I'm guessing he just didn't have an equivalent scenario, or that his battery was already warm enough from driving and he simply didn't make a note of it (highly likely). Before heat pumps, it was easier to still have leftover heat from the previous Supercharger session, so preconditioning is less likely on long trips like he does. However with the heat pump system drawing it down to 15C, it will need to actively heat for more Supercharging sessions than the older models. Yes, that does mean the 2021 model has a scenario where it's using more power than the older models. Weird eh? It might balance out.
  • He didn't mention it, but his overnight sleep it was clearly using the motors as a n actively powered heat source while parked (they're above 40C while everything else is cold, including the battery). This is strange - it would be less efficient than a PTC element like on the older Model 3s. I guessed this would be the case around and below freezing temps (it was at freezing at that point in the video), but this isn't how I thought it would work. Interesting. It's also possible that it was using this heat for something else (e.g. the battery).
I kind of wonder what a freezing cold 2021 Model 3 will do. My 2019 will actively heat the pack to about 0C, then just with waste heat from the motors after that (which takes a long time). I already think this is a massive waste of energy for short hops - I drive 4km/day right now, using 30-50km of range to do so (a large chunk of which is actively heating the darn battery just to 0C). I really, really hope the 2021 ones do not try to actively heat the pack to 15+C on similar trips just to use as a heat source - that would be a gargantuan waste of energy for short commutes.

It's worth mentioning that I disagree with a lot of Bjorn's observations, so I have a bias already. He has a large following and has made some very false suggestions/observations (not claims) regarding Model 3 - nothing super detrimental, but mildly annoying given his very large following that takes his word on most things.

His takeaway that the trip meter says 172Wh/km so it's done better than the previous models is seriously flawed. The trip meter does not count usage while parked. I don't doubt that it is more efficient in mild winter temps (which it seemed like he was in - heavy snow, wet roads, 0C when he woke up near noon) and especially on long trips with lots of DC fast charging (which dumps tons of heat in the battery to scavenge). Basically, this trip of his was the best case scenario for the heat pump system. I'd put a huge "To Be Determined" label on how it compares in daily commuter scenarios in colder temperatures.

And this concludes my wall of text / thought dump. Excited to see more data with the heat pump behaviour!

What I like about Bjorn's videos are that he shows raw data and why he thinks the way he does. People on this forum just spit out info that has no backing besides, "I think", "I see", etc, etc. We all know that people are wrong so I take personal antidotes with a huge amount of salt. Bjorn also has tested A LOT of Teslas and other EVs. I've been watching Bjorn since more than 6 years ago when he first had a S then a X.

I take his info and analysis with more weight than other people because he has experience.
 
What I like about Bjorn's videos are that he shows raw data and why he thinks the way he does. People on this forum just spit out info that has no backing besides, "I think", "I see", etc, etc. We all know that people are wrong so I take personal antidotes with a huge amount of salt. Bjorn also has tested A LOT of Teslas and other EVs. I've been watching Bjorn since more than 6 years ago when he first had a S then a X.

I take his info and analysis with more weight than other people because he has experience.

I like the same points you mentioned. Don't get me wrong, I watched a lot of his videos before ever owning a Tesla too. It was only once I had my own data I saw "oh... what he said isn't actually correct". Which again, isn't super detrimental anything - he's not making rigid claims most of the time. He has the setup and the following to present that data "easily" now as part of his, uh, "workflow" I guess is the right word? Most of us don't, and it shouldn't be discounted how much effort it is to put up videos with data like that.
 
I like the same points you mentioned. Don't get me wrong, I watched a lot of his videos before ever owning a Tesla too. It was only once I had my own data I saw "oh... what he said isn't actually correct". Which again, isn't super detrimental anything - he's not making rigid claims most of the time. He has the setup and the following to present that data "easily" now as part of his, uh, "workflow" I guess is the right word? Most of us don't, and it shouldn't be discounted how much effort it is to put up videos with data like that.

@camalaio

Just posting to say its good to see you still around. I hadnt seen you for a while, and thought we lost you somewhere around the 47th response you made to someone posting on the topic of battery degradation (lol). Glad to see you are still visiting the site and dumping those (wall of texts), lol.

I enjoy reading your take on many things. Hope you continue to dump this data on us.
 
@camalaio

Just posting to say its good to see you still around. I hadnt seen you for a while, and thought we lost you somewhere around the 47th response you made to someone posting on the topic of battery degradation (lol). Glad to see you are still visiting the site and dumping those (wall of texts), lol.

I enjoy reading your take on many things. Hope you continue to dump this data on us.
Hah! I appreciate the words. I'll derail for one more post just to respond :) (also, what, you're a mod now? 'grats!)

I remember you saying something like hope I don't get burnt out posting on here, then I said I wouldn't... guess who was wrong :p it was a nice break.

That said, I'm happy to be back here. It beats dealing with my current Facebook feed. By a lot. I have the mental room for only one, not both haha.
 
The thing I really like about Bjorn is if he thinks something is a certain way and then after his "testing" he finds out that isn't the case he will point it out saying his previous assumptions were incorrect and explains why he came to the conclusion and what made him change his mind. I understand what he is sharing is based on what he is seeing given what he is doing. Honestly that honesty in what he is doing is great. I watch him first for entertainment value, but then he throws in deep EV information as well :)

Oh and camalaio I couldn't agree more, I wish we had a "Short Trip" button, even if it was buried in some menu. Having the Tesla sit outside 12 hours, leaving at 1am in 11F (-11C) and driving home 3 miles, just let me drive home without trying to heat the battery up.
 
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With Tesla "hiding" a lot of the behind the scenes details, a lot of decisions are made for us. For 96% of users this probably is a good decision. For those of us that look deeper, perhaps an "advanced mode?"
 
Recent research into capacitive rapid recycling has led to hybrid arrays which seem to combine modified Li-ion cells and capacitors. Could cells charge capacitors which can then be flash-discharged to obtain power? Just asking...
In theory but from what I've read, and i'm just a layman, the benefit of doing so doesn't outweigh the complexity, increased cost, and relatively small amount of energy a capacitor can store.