Preconditioning and Charging the Car

[artsci]

These are my expectations:

1. While the my Tesla is preconditioning and smart charging it will prepare my breakfast.
2. When I finish my breakfast it will wash and dry the dirty dishes.

 

[GaryREM]

The following are my expectations for "Smart" preconditioning:

1. I should be able to look at the calendar (or have some other mechanism) to see all the preconditioning events that the car has scheduled for me or that I have explicitly scheduled.
2. The calendar event indicates the time I am leaving and the desired cabin temperature.
3. The car should figure out when to start preconditioning so that the desired cabin temperature is reached at the moment I wish to leave.
4. I should have the option of scheduling a series of recurring events, i.e. my morning commute to work.
5. I should have the ability to skip a scheduled event, e.g. I am not going to work today.
6. I should have the option to specify if preconditioning takes place only if the car is plugged in. In this case, the car will need to start charging the car early enough so that it will replace all the energy that will be consumed by preconditioning. I don't want preconditioning to decrease my range. In the winter, precondition can take several kWh of energy when temperatures are below 0 F.
7. I should be able to access a web site to look at my calendar and update it.

I assume you have sent this request to Tesla...

 

[JohnQ]

I would suggest you are over thinking this. It's really not complicated and requires minimal action on your part. If you're on a 50A circuit, set your timer for 12:01am. Set your charge amount slider to 90% (or whatever you're comfortable with). Plug in your car. Go to sleep. Your car will be charged before 7am when rates go up unless you have an extremely low state of charge when you plug in.

When you're making your coffee on winter mornings, turn on the heater from the app so the car is toasty when you go to your garage. If you want to ensure you're not drawing any shore power, unplug before doing so...the energy will come from the battery.

This is my approach and it works swimmingly. If you leave your car plugged in for a week while you're on vacation it will initiate top up charges at 12:01 when it's needed.

 

[Andyw2100]

This is the scenario I am concerned with. I drive around in the morning and come home in the afternoon. I now want to charge the car until 4:00 pm, at which time peak hours begin, so I have enough range for trips later in the evening. There is no way to tell the car to stop charging at 4:00 pm. If I forget to unplug it, I am going to be very upset stuck with a large electric bill. In addition, smart preconditioning is unreliable. It may decide to start preconditioning the car during peak hours. I have no choice but to use a timer.

You can deal with this issue appropriately by figuring out how much the car would be able to charge by the time the rates go up, and then setting the charge limit to something below that, so that the charging stops before your rate goes up.

It sounds like you may also be interested in this thread: Would you use battery heating if it were available?

 

[lphe]

The whole point of preconditioning is to use power from the wall outlet rather than from the battery so you don't lose range. When it is -20 F, from what I have read, the car is going to use 12 kW of power to heat the cabin and the battery. It is going to take a lot of energy and time to warm everything up. The charger cannot supply that much power (especially when I am away from home and do not have access to outlets that can provide more than 1.4 kW of power). Remote starting the car will eat up lots of range on top of the significant reduction in range resulting from driving in cold weather. The car should be smart enough to precondition the car without reducing the range available from the battery. I want to maintain as much range as possible in cold weather. I don't want my range cut in half.

The car should automatically manage energy for me. It should not draw power during peak electric rates and it should only use power from the wall outlet to precondition the car. I shouldn't have to manually intervene. Other cars already have these features.

 

[lphe]

I also have another question about driving in cold weather. Does the car automatically manage air recirculation to simultaneously reduce energy use and minimize window fogging? When it is -20 F, it takes a tremendous amount of energy to heat outside air that is being drawn in when recirculation is off. If instead the car recirculates cabin air, energy use for heating is dramatically reduced and the car will have much greater range. The downside of recirculating air is that the windows will eventually fog up. There must be a balance between using recirculated air to reduce energy consumption and drawing in outside air to prevent windows from fogging up. Again, I want to maximize range in extreme cold.

 

[JohnQ]

The whole point of preconditioning is to use power from the wall outlet rather than from the battery so you don't lose range. When it is -20 F, from what I have read, the car is going to use 12 kW of power to heat the cabin and the battery. It is going to take a lot of energy and time to warm everything up. The charger cannot supply that much power (especially when I am away from home and do not have access to outlets that can provide more than 1.4 kW of power). Remote starting the car will eat up lots of range on top of the significant reduction in range resulting from driving in cold weather. The car should be smart enough to precondition the car without reducing the range available from the battery. I want to maintain as much range as possible in cold weather. I don't want my range cut in half.

The car should automatically manage energy for me. It should not draw power during peak electric rates and it should only use power from the wall outlet to precondition the car. I shouldn't have to manually intervene. Other cars already have these features.

The only thing the car doesn't do for you in this scenario is determine whether to preheat from shore power or battery based on time of day. If you're car is plugged in, and you decide to pre-heat, it will draw from shore power. In what circumstances are you trying to maximize range? Do you have an exceptionally long commute where you regularly need the full charge or is it only for occasional road trips? If you're well within range for a commute then this is a moot point as it doesn't matter whether you draw from shore power or the battery for range purposes. On the other hand, if you need your full charge on a daily basis then you simply have to heat the battery from shore power.

Regarding 110V outlets, as you say there's a limit on power delivery. If you're not driving the car for a few hours, simply plug in, move your charging slider above it's current level (say from 90% to 100%) and the car will start charging. It will warm the battery first so it can accept the charge. Simply unplug and start driving with a warm battery. It will take longer to warm the battery from a low power outlet but that's just physics.

 

[lphe]

If preconditioning requires 12 kW of power and the wall outlet cannot provide that much power, the car will need to begin preconditioning sooner using less power. For example, it might take 0.5 hours at 12 kW to precondition the car. If the outlet can only provide 6 kW of power, then preconditioning might take one hour. For a 120 volt outlet, the car will need to store additional charge in advance in the battery to precondition the car. It may need to start charging the car four hours in advance above the normal charge level to provide the energy needed for preconditioning. The car should automatically manage energy for me.

 

[JohnQ]

Let me restate your points to be sure I understand. The car should know when you need to drive, either by monitoring your patterns or by you telling the car via a scheduling function. Based on that information, the car should start preheating the battery far enough in advance, taking into account available power from the outlet, to have the battery fully preheated from shore power. I'll leave out the TOU issue since that can make the calculation more complex regarding when to draw from shore power. I think that sounds right.

I'm not sure I understand the point about storage of additional charge--either you want to charge to 90% or to 92%. It sounds like you're asking for a built-in buffer to account for projected battery heating. Hard to accomplish when the car knows it's storage temperature (say, in a garage) but not the ambient temperature. I suppose it could poll the internet for the temp at your indicated drive time but that just seems needlessly complex and dependent on an active connection which it may not have.

If that's stated correctly then you should send an enhancement request to Tesla. It's certainly possible but is dependent on some features that others have asked for but haven't been implemented such as charge completion scheduling. One thing that concerns me about the charge completion scheduling is the required assumption of a constant power source (even taking into account potential tapering for a 100% charge). As you know, Tesla throttles charge rate if it detects an anomaly. I'd be pretty pissed if I had to drive early with a given range and the car hadn't reached it because charge amperage was backed off from 40A to 30A. So, I might not personally use it when range was critical. But then I really don't care about battery heating if range isn't critical.

 

[lphe]

Thank you for your response. Yes. I would like the car to be ready at a scheduled time with a specified state of charge, the battery warmed up, and the passenger compartment heated to a specified temperature. I don't want to see 85% state of charge (due to preconditioning) when I start out when I set it to be 90%. The car will have to compute when to begin preconditioning based on the power available from the wall outlet (which will in general vary with the location the car is parked). If you are using 120 volts to charge the car, 1.4 kW of power is not going to do much to warm the car, especially if the car is pulling in and warming outside air into the cabin. No matter how early you start preconditioning, the car is never going to warm up to 72 F if the car is limited to 1.4 kW of power. The car will have to anticipate this and start charging a few hours early, charging above 90% state of charge. The car then can use this excess state of charge to warm up the car by the scheduled time and have 90% state of charge remaining.

I'm not sure what charge completion scheduling is.