Hey Elon, how about a "Hysteresis" charging option

[mswlogo]

Yes, it will initiate a charge on its own. I believe the number is 3%, but I don’t recall for sure. Been a long time since I experimented with it.

I didn’t know opening the door would initiate a charge. I do know that opening the door will start the HVAC and start warming the battery. I can see it on the dash, even with a charge scheduled in the future. Many appreciate using shore power to get this going for range reasons.

Does it keep warming and charging if you don’t get in and just close the door?

I hear what your saying on overall energy wasting. I’m not convinced a wider hysteresis band is the solution.

Maybe charge slower so it doesn’t need a warm pack?

Or a battery pre-heat button to press before a trip so it doesn’t have to assume shore power is the right choice?

I really have no idea what it would really save. I highly suspect it much better than targeted charging finish in order to regain regen. I only noticed it do this once top off on it's own once. Maybe it was on the verge of doing the 3% thing you mentioned and when I opened the door it started cabin heat and it dropped enough to trip that 3% re-top off. I might have done some work in the car putting in a sunshade and it may have dropped enough.

I believe did shut the door and it look like it was just gonna do it's normal charge thing.

Setting the current limit low is a very interesting idea. That might just work.

Keep in mind the opening door thing was just one example and if it doesn't happen that often it's not a big deal. I think the hysteresis control could still be very helpful because of the overhead (Extra energy) in setting up a cold charge. You don't want to do that more than needed. Now it could also automatically lower the current to avoid heating. But it doesn't appear to do that.

As many Model S owners have suggested, just don't plug it in. I don't want to not plug it in. And the only way to get it to not charge is to constantly fiddle with the high limit.

 

[jgs]

this is extremely uncommon

Cool, would you mind sharing the link to detailed stats about Tesla owners' daily charge depletion? I wasn't aware anyone but Tesla had that information available.

We have not seen reports of folks reporting their car will not charge on a 120v receptacle in the winter

It takes a while (many minutes) before the mph number gets up to nominal when charging on a household receptacle, though. I assume that to be heating time. I also imagine (though battery management is not my forte) that you don't have to warm the battery as much to get it to accept 1.5kW.

why don't you just unplug it when you don't want it to draw energy

My own answer to this is, it's because I want to have a completely regular routine -- get out of car, plug in, walk away. I do this even if I know I'll be going out again soon. The reason is because if I establish it as a set habit, the chance I'll forget to plug in when I want to is very low.

 

[mswlogo]

My own answer to this is, it's because I want to have a completely regular routine -- get out of car, plug in, walk away. I do this even if I know I'll be going out again soon. The reason is because if I establish it as a set habit, the chance I'll forget to plug in when I want to is very low.

Exactly !!!

 

[BerTX]

Exactly !!!

I use Dashboard for Tesla (only for Android) rather than the Tesla app, and it does not have the ability to do this currently, but the developer, @SG57 , might be interested in adding it to the app if you think it would be useful. I see no reason why the API could not do this.

Of course, if you have an iPhone, "I got nothin' for ya, head back to camp".

 

[mswlogo]

I use Dashboard for Tesla (only for Android) rather than the Tesla app, and it does not have the ability to do this currently, but the developer, @SG57 , might be interested in adding it to the app if you think it would be useful. I see no reason why the API could not do this.

Of course, if you have an iPhone, "I got nothin' for ya, head back to camp".

I develop apps on both Android and iOS. Don't get me started... I switched from Android to iOS only to learn how to support iOS customers. I will NEVER go back after what I've seen under the hood.

But you are right this could possibly be done via an app by messing with the one limit and monitoring the battery level. All it has to do it drop the limit (say it's normally at 80%) by some large amount (say to 50%) until the battery drops down by the user specified low limit (say 70%). Once it does drop below 70% the app just has to move the limit back up to normal (80%) and the next time it gets plugged in (or scheduled) it would charge. Basically it would do what I'm doing manually.

 

[BerTX]

The HVAC (both heater and a/c) run from the HV battery directly. The car will "charge" to make up the difference, so yes if the heater comes on when you open the door, then it will often mean the car starts charging. Perhaps if the battery is charged to it's appointed level, then it will heat for a short time before charging, I don't know.

But the HVAC does not run directly from the charging cord, there is no connection.

Okay, I got some disagrees to this post, which isn't very helpful or educational to me. This is a Model 3 thread -- is the system different than it is on the Model S? I don't know what the disagreement is.

 

[jgs]

Okay, I got some disagrees to this post, which isn't very helpful or educational to me. This is a Model 3 thread -- is the system different than it is on the Model S? I don't know what the disagreement is.

I can't speak for those who clicked "disagree", I never use it myself since I find it entirely useless. However my own casual observation of my Model S's behavior over the years is that kicking HVAC on does not initiate charging. Sure, the energy may well follow the route you suggest, but the car only draws enough current to run the HVAC, not to add charge. And when you turn off HVAC, the battery doesn't charge.

I just confirmed this is how it works with the Model 3, by experiment. Our Model 3 is currently at around 65% SOC, set to charge to 80%. It was charging, actually, but I stopped it. So it's got quite a bit of charge required before it reaches its target. I went out and sat in it with the heat on. It reported drawing 31A, not the full 40A. Left the car and let HVAC turn off. Confirmed it's not charging. Finally, I manually started it charging again since I actually do want that 80% SOC and it's happily pulling the full 40A now.

I think for all practical purposes, @Rocky_H's description of the car running the HVAC from wall current and not charging is the more useful one. I think for the most part when we speak of "charging" the car we mean "increasing the SOC of the battery pack".

 

[mswlogo]

I can't speak for those who clicked "disagree", I never use it myself since I find it entirely useless. However my own casual observation of my Model S's behavior over the years is that kicking HVAC on does not initiate charging. Sure, the energy may well follow the route you suggest, but the car only draws enough current to run the HVAC, not to add charge. And when you turn off HVAC, the battery doesn't charge.

I just confirmed this is how it works with the Model 3, by experiment. Our Model 3 is currently at around 65% SOC, set to charge to 80%. It was charging, actually, but I stopped it. So it's got quite a bit of charge required before it reaches its target. I went out and sat in it with the heat on. It reported drawing 31A, not the full 40A. Left the car and let HVAC turn off. Confirmed it's not charging. Finally, I manually started it charging again since I actually do want that 80% SOC and it's happily pulling the full 40A now.

I think for all practical purposes, @Rocky_H's description of the car running the HVAC from wall current and not charging is the more useful one. I think for the most part when we speak of "charging" the car we mean "increasing the SOC of the battery pack".

Interesting. I'd be very surprised it would pull 31A just for cabin heating. I have a friend that knows someone that works at Tesla and he said there are 2 independently controlled 1000 watt heaters in the cabin. That 31A amps is doing something else besides heating the cabin. That is like 7500 watts.

What was your guestimate on battery temp?

I think another way to test would be to leave the cabin on for a good while with windows open with battery at set point see if the battery drops quickly. It should drop fairly fast, I've seen heat use as much as 100 wh/mi.

It may be tricky to prove that it always runs off battery or not, but thinking about it, your suggestion it's always off battery does make sense. It would be fairly complex it have it switch over and would be much simpler to always go off battery.

Regardless that 31A is to high for just HVAC.

 

[Sophias_dad]

Just as a datapoint, I plugged my 3 into the HPWC and set it to draw no more than 10 amps as an experiment. It gained ZERO miles in a half hour. I didn't need the charge that badly, so I terminated the experiment.

The temp was 15f or so, and the battery was not notably warm from driving.

A few days later, with the temp at 30f, 15 amp/240 volt charging got me a pretty slow charge. I didn't see where it peaked, but after at least 45 minutes, it showed it had very slightly charged the battery, even though it still said 0mi/hr. I forgot about it and it ended up finishing the charge quite some time later.

There's no chance you'll get any charge in cold weather from a 120 volt outlet. Even prewarmed from driving, the battery cools as its not quick-charged. Saw this happen once at work, where I plugged into a pathetic underpowered J1772 outlet(183 volts!). It started out at 6kw, and in an hour or so it was down to 4kw and I presume this was due to the battery cooling(~30f, IIRC), even while being charged.

 

[jgs]

What was your guestimate on battery temp?

It had been charging for a couple hours already, so presumably the battery should already have been heated as much as it needed.

Oh by the way, exterior temperature is 26F at the moment. And the cabin was dead cold, I must have leaned on a window switch, one of the windows was open. :-o

 

[jgs]

There's no chance you'll get any charge in cold weather from a 120 volt outlet.

Although your anecdotes have caused me to rack my brain wondering if I’m losing my mind, nonetheless: I’ve done it, as previously described. It was pretty snowy so the temps were probably around high twenties.

 

[eprosenx]

Okay, I got some disagrees to this post, which isn't very helpful or educational to me. This is a Model 3 thread -- is the system different than it is on the Model S? I don't know what the disagreement is.

My apologies for clicking "Disagree" and then not providing an explanation. I got pulled onto a conference call and did not have time to finish responding. ;-)

So I charge my Model 3 LR every day to 80% on my Wall Connector (60a circuit) when I get home. It sits outside all the time. I often come back to the car to load/unload it even when I am not going to drive it. I have never seen it kick in charging just because I opened the door (which kicks on HVAC) or because I manually kicked on HVAC from the app.

It is actually annoying as every morning now that it is winter I start out with like 78% battery instead of 80% as it seems to settle down a bit overnight after the battery cools. Even extended "warming up" of the car from shore power does not ever kick in the actual charging.

I do know it is drawing shore power because I can hear it click the Wall Connector when it kicks in and it shows amperage draw on the Tesla screen (but not as much as it would draw if charging - always some lower #), and I also have a Sense Home Energy Monitor that let's me see usage on my phone.

I have posted a few screen shots of my Sense Home Energy Monitor data here from when I fire up the heat in the AM using the app. You can see the car draws a lot of shore power to start if it is really cold and then it ramps down as some combination of the cabin and the battery come up to temp. It is very interesting since it seems to oscillate up and down a lot as it is "hunting" for the right cabin temp I assume. This looks *nothing* like what battery charging looks like. Battery charging is a "flat line" at whatever current you set (until it tapers off if the battery is super full or perhaps too cold - but that would be a taper up as it warmed?)

Shore power usage during morning warmup

It is amazing how much current the car can pull from shore power to warm up! Though the M3 battery does seem to take forever to come up to temp to get full regen.

To your point, I am curious how the DC power bus works in the Model 3: If running HVAC and battery heating off shore power, does it not connect the battery to the DC bus at all (and just energize the DC bus using the inverters in the charger)? Or is the battery engaged to the DC bus, but they are just having the inverters track the usage of the HVAC/battery heating closely so as to not be charging or discharging the battery even though it is on the common bus?

inquiring minds want to know!

 

[eprosenx]

Saw this happen once at work, where I plugged into a pathetic underpowered J1772 outlet(183 volts!). It started out at 6kw, and in an hour or so it was down to 4kw and I presume this was due to the battery cooling(~30f, IIRC), even while being charged.

183 volts!!!

Something is seriously wrong there. Even if that started out at 208v nominal that is a 12% voltage drop which is crazy.

Either there is some loose connection, or someone vastly mis-engineered that from a voltage drop standpoint.

Did the car alert you to any issues and drop down the charging rate? What voltage did that start off at before charging ramped up?

 

[Canuck]

It is actually annoying as every morning now that it is winter I start out with like 78% battery instead of 80% as it seems to settle down a bit overnight after the battery cools.

Why is it annoying to have 78 instead of 80? Is it an OCD or range issue? I can see it being an OCD issue since stuff like that bothers me too but I guess we just have to deal with it. If it's a range issue, set it to 82 or even 85 and don't worry about it. It won't fall below 80. The measurements of battery charge is not like a float in a tank of gas -- it's tough to measure trapped energy accurately so it's based on algorithms. Bottom line: don't sweat a few percent, or at least try not to.

Interesting thread overall.

 

[mswlogo]

To your point, I am curious how the DC power bus works in the Model 3: If running HVAC and battery heating off shore power, does it not connect the battery to the DC bus at all (and just energize the DC bus using the inverters in the charger)? Or is the battery engaged to the DC bus, but they are just having the inverters track the usage of the HVAC/battery heating closely so as to not be charging or discharging the battery even though it is on the common bus?

inquiring minds want to know!

That's exactly what I was thinking it might be doing. Because from the outside it feels like "shore power". I also agree it uses a lot more juice at times than just the cabin heaters. Which to my understanding is 2000 watts (3rd hand info).

It would make sense for everything to always run off the "DC Power" bus. Less parts to fail. Even if it's some loss of efficiency pre-heating cabin or battery. Reliability and cost are major factors too.

Now, does it disconnect the battery or regulate the inverter to not affect battery level, who knows.

It's also better to measure what is going into the car than what the car is saying.

 

[eprosenx]

That's exactly what I was thinking it might be doing. Because from the outside it feels like "shore power". I also agree it uses a lot more juice at times than just the cabin heaters. Which to my understanding is 2000 watts (3rd hand info).

Btw, I am going to challenge that the 2000w thing for the cabin heater. That is not a lot of heating power. I suspect the M3 has at least 4000w of heating capacity. Some online searches suggest 4300 watts, but that could be inaccurate.

 

[eprosenx]

Why is it annoying to have 78 instead of 80? Is it an OCD or range issue? I can see it being an OCD issue since stuff like that bothers me too but I guess we just have to deal with it. If it's a range issue, set it to 82 or even 85 and don't worry about it. It won't fall below 80. The measurements of battery charge is not like a float in a tank of gas -- it's tough to measure trapped energy accurately so it's based on algorithms. Bottom line: don't sweat a few percent, or at least try not to.

Interesting thread overall.

100% OCD. ;-)

I only commute 30 miles a day.

I wonder if they could temperature compensate the battery measurement reading... (but yes, lots of other things I would rather them work on) ;-)

 

[BerTX]

My apologies for clicking "Disagree" and then not providing an explanation. I got pulled onto a conference call and did not have time to finish responding. ;-)

So I charge my Model 3 LR every day to 80% on my Wall Connector (60a circuit) when I get home. It sits outside all the time. I often come back to the car to load/unload it even when I am not going to drive it. I have never seen it kick in charging just because I opened the door (which kicks on HVAC) or because I manually kicked on HVAC from the app.

It is actually annoying as every morning now that it is winter I start out with like 78% battery instead of 80% as it seems to settle down a bit overnight after the battery cools. Even extended "warming up" of the car from shore power does not ever kick in the actual charging.

I do know it is drawing shore power because I can hear it click the Wall Connector when it kicks in and it shows amperage draw on the Tesla screen (but not as much as it would draw if charging - always some lower #), and I also have a Sense Home Energy Monitor that let's me see usage on my phone.

I have posted a few screen shots of my Sense Home Energy Monitor data here from when I fire up the heat in the AM using the app. You can see the car draws a lot of shore power to start if it is really cold and then it ramps down as some combination of the cabin and the battery come up to temp. It is very interesting since it seems to oscillate up and down a lot as it is "hunting" for the right cabin temp I assume. This looks *nothing* like what battery charging looks like. Battery charging is a "flat line" at whatever current you set (until it tapers off if the battery is super full or perhaps too cold - but that would be a taper up as it warmed?)

Shore power usage during morning warmup

It is amazing how much current the car can pull from shore power to warm up! Though the M3 battery does seem to take forever to come up to temp to get full regen.

To your point, I am curious how the DC power bus works in the Model 3: If running HVAC and battery heating off shore power, does it not connect the battery to the DC bus at all (and just energize the DC bus using the inverters in the charger)? Or is the battery engaged to the DC bus, but they are just having the inverters track the usage of the HVAC/battery heating closely so as to not be charging or discharging the battery even though it is on the common bus?

inquiring minds want to know!

I have read and seen wiring diagrams indicating that the Model S/X does use the power directly from the HV battery. I assume this is a successful system. It's possible they changed it for the Model 3, but doing that would require more complexity and adding additional converter/inverter capacity or new parts, plus changing the design of the heater and a/c. The idea of the Model 3 is to decrease cost and complexity, so I doubt this would happen. They did eliminate the battery heater, which seems an indicator that they wanted to simplify and decrease parts overall.

If you do not have the car plugged in and run the heater, then the battery DIScharges. Keeping that from happening by putting power into the battery via the charging system is called charging in my book. I understand your interpretation that charging means putting additional power into the battery to increase SOC and agree that it doesn't necessarily do that.

 

[Sophias_dad]

183 volts!!!

Something is seriously wrong there. Even if that started out at 208v nominal that is a 12% voltage drop which is crazy.

Either there is some loose connection, or someone vastly mis-engineered that from a voltage drop standpoint.

Did the car alert you to any issues and drop down the charging rate? What voltage did that start off at before charging ramped up?

No, its always 183V... Its on the same post as a 277V HPWC, so I assume they have a 3:2 step-down transformer, either too cheap or too lazy to get a 6:5....

 

[diamond.g]

I develop apps on both Android and iOS. Don't get me started... I switched from Android to iOS only to learn how to support iOS customers. I will NEVER go back after what I've seen under the hood.

But you are right this could possibly be done via an app by messing with the one limit and monitoring the battery level. All it has to do it drop the limit (say it's normally at 80%) by some large amount (say to 50%) until the battery drops down by the user specified low limit (say 70%). Once it does drop below 70% the app just has to move the limit back up to normal (80%) and the next time it gets plugged in (or scheduled) it would charge. Basically it would do what I'm doing manually.

I would think that apps that have to connect to the car to do that charging managing would have to keep the car awake (or wake it up more than the car would on its own) thus contributing to vampire drain.

Btw, I am going to challenge that the 2000w thing for the cabin heater. That is not a lot of heating power. I suspect the M3 has at least 4000w of heating capacity. Some online searches suggest 4300 watts, but that could be inaccurate.

Hmm, I was under the impression that it was a 6kW heater, but I saw the InsideEVs article the 4300W came from. Sadly no one has been able to say if there is a temp diag mode like on the S/X that would show that kind of information.