Preheating Battery plugged in?

[VT Tessie]

Hello -

I am wondering if I should be preheating the battery before driving with it plugged in, or not.

I recognize that preheating without being plugged in reduces the battery charge, but if I am doing so while plugged in at certain times of the day, the electricity charge is higher. I also wonder if I am adding a "charging cycle" by plugging it in to preheat the battery.

I have been told that preheating it while plugged in warms the battery directly from the energy coming in, and not through the battery itself. Could someone help explain?

 

[canbonbon]

I don't see any preheating "battery" option. All I see is that you can schedule climate. Maybe it does both during Climate control but not sure. I would like to know this as well. I have seeing battery warming icon come up during charging (when its very cold outside) but I don't know how to force it

 

[jcanoe]

When you Precondition via the Tesla app or using Scheduled Departure Preconditioning there are two things that may happen:

The passenger cabin will be heated or cooled to your desired temperature. If the Tesla vehicle determines that the battery needs to be warmed for better performance while driving then this will happen automatically as part of the Preconditioning.

As you noted, your Tesla vehicle does not have to be plugged in to be able to use the Preconditioning function.

If the ambient temperature is cold but not too cold then battery warming won't take place when not plugged in while preconditioning. If the ambient temperature falls below 32F/0C then in my experience the battery will be warmed even if not plugged in. The battery will only be partially warmed, i.e. to 50F/10C. Further warming is unnecessary; would take longer and use more energy.

Precondition (whether plugged in or not) for your comfort and to melt snow and ice from the vehicle windows. The Tesla vehicle will automatically warm the battery as required either during preconditioning or while driving.

Turn on the blended friction braking feature under Pedals & Steering. That way the Tesla Model Y will slow as expected regardless of the battery temperature and the reduced regenerative braking that goes with a cold battery. Before blended friction braking was available you could spend 40 minutes preconditioning and still have limited/almost no noticeable regenerative braking when you started to drive. Now, you can just drive and preconditioning can be accomplished faster and consume less energy (either from the grid or from the battery.)

Precondition while plugged in whenever possible. This will use the available power for the Level 1/Level 2 charging circuit and only draw power from the high voltage battery as required. Example: If you charge at 9.6kW rate but preconditioning with battery warming requires 15kW then ~5.5kW will have to be provided by the battery during the time that Preconditioning is active.

When considering charge/discharge cycles battery manufacturers and lab studies use a full charge to 100% and discharge down to the lowest allowable charge. Daily driving, charging and discharge cycles and also preconditioning only amount only a small faction of a full charging cycle. Not worth worrying about.

 

[LoudMusic]

Hello -

I am wondering if I should be preheating the battery before driving with it plugged in, or not.

YES! Preferably plugged in.

I recognize that preheating without being plugged in reduces the battery charge, but if I am doing so while plugged in at certain times of the day, the electricity charge is higher.

Energy is energy, whether it's coming from the battery or the wall. If your electricity fees vary throughout the day there might be incentive to charge the battery at night, and precondition without charging in the morning. But as @jcanoe said, it's a minimal amount of energy for preconditioning. I prefer to have the car plugged in and able to draw energy from the wall whenever possible.

I also wonder if I am adding a "charging cycle" by plugging it in to preheat the battery.

A cycle is measured 0-100-0%. Partial cycles are cumulative. Preconditioning probably uses 2% on a typical day. The vehicle's battery is expected to do 1,500 cycles without any issues, not counting minor capacity degradation.

I have been told that preheating it while plugged in warms the battery directly from the energy coming in, and not through the battery itself. Could someone help explain?

There's a lot to understand here but the short version is, the preconditioning begins using energy from the battery, and when the battery level goes down while the car is plugged in the charger will begin charging the battery.

 

[SkyDog]

I am wondering if I should be preheating the battery before driving with it plugged in, or not.

I agree with the replies so far, but am wondering what you are trying to accomplish - warm the cabin for comfort , or something else?

I'll warm the cabin up on really cold mornings, whether it's plugged in or not - I don't think it uses that much power for 5 or 10 minutes of warming. I don't worry about the battery being warmed up, that happens while driving, and I just compensate for the reduced regenerative braking until the battery is warmer.

 

[E90alex]

Precondition if you want the cabin more comfortable is the bottom line. The energy used is minuscule, like probably less than 1kW for 10-15 mins of preconditioning.

If it’s below freezing you may get better regen if you precondition, but other than that you don’t need to concern yourself with the battery temperature.

A charge cycle is a full cycle (100%) equivalent, not how many times it’s plugged in. Eg 5x charges of 20% is a battery cycle.

 

[VT Tessie]

I don't see any preheating "battery" option. All I see is that you can schedule climate. Maybe it does both during Climate control but not sure. I would like to know this as well. I have seeing battery warming icon come up during charging (when its very cold outside) but I don't know how to force it

When you Precondition via the Tesla app or using Scheduled Departure Preconditioning there are two things that may happen:

The passenger cabin will be heated or cooled to your desired temperature. If the Tesla vehicle determines that the battery needs to be warmed for better performance while driving then this will happen automatically as part of the Preconditioning.

As you noted, your Tesla vehicle does not have to be plugged in to be able to use the Preconditioning function.

If the ambient temperature is cold but not too cold then battery warming won't take place when not plugged in while preconditioning. If the ambient temperature falls below 32F/0C then in my experience the battery will be warmed even if not plugged in. The battery will only be partially warmed, i.e. to 50F/10C. Further warming is unnecessary; would take longer and use more energy.

Precondition (whether plugged in or not) for your comfort and to melt snow and ice from the vehicle windows. The Tesla vehicle will automatically warm the battery as required either during preconditioning or while driving.

Turn on the blended friction braking feature under Pedals & Steering. That way the Tesla Model Y will slow as expected regardless of the battery temperature and the reduced regenerative braking that goes with a cold battery. Before blended friction braking was available you could spend 40 minutes preconditioning and still have limited/almost no noticeable regenerative braking when you started to drive. Now, you can just drive and preconditioning can be accomplished faster and consume less energy (either from the grid or from the battery.)

Precondition while plugged in whenever possible. This will use the available power for the Level 1/Level 2 charging circuit and only draw power from the high voltage battery as required. Example: If you charge at 9.6kW rate but preconditioning with battery warming requires 15kW then ~5.5kW will have to be provided by the battery during the time that Preconditioning is active.

When considering charge/discharge cycles battery manufacturers and lab studies use a full charge to 100% and discharge down to the lowest allowable charge. Daily driving, charging and discharge cycles and also preconditioning only amount only a small faction of a full charging cycle. Not worth worrying about.

Excellent - I appreciate your insights. I live in VT and it is often below 32F. I also live at the top of a mountain and going down without preconditioning results in a lot of braking if things are not preconditioned - so I try to precondition a lot in the winter.

I agree with the replies so far, but am wondering what you are trying to accomplish - warm the cabin for comfort , or something else?

I'll warm the cabin up on really cold mornings, whether it's plugged in or not - I don't think it uses that much power for 5 or 10 minutes of warming. I don't worry about the battery being warmed up, that happens while driving, and I just compensate for the reduced regenerative braking until the battery is warmer.

I am mostly trying to accomplish having a warm enough battery so the regen works. From where I am up in the hills, it can take 15-20 minutes of driving until the regen kicks in, and I much prefer to drive with it working (just preference). Warming up the cabin is not so much a big deal. The seat and steering wheel warmers do a good job.

My original question mostly was about preheating with the car plugged in or not. Is it better for the battery to do that with the car plugged in or not, or does it not matter.

I wish Car Talk was still on the air. This would have been a perfect question where the girlfriend calls in and says that her boyfriend tells her that it is better to precondition the car with it plugged in, and the girlfriend wonders why this is so. (As this is the situation

 

[Leeclanual]

Keep it plugged in

 

[jcanoe]

Precondition when plugged in whenever possible. In cold weather the power demands of preconditioning will likely exceed the maximum 11.5kW for Level 2 charging. Any additional power needed will come from the battery. In this case you would be using some power from the battery for preconditioning and battery warming whether you know it. In milder temperatures with no battery warming taking place then preconditioning while plugged in for Level 2 charging may not need to use any power from the battery.

Adding charge to the battery and pulling power out of the battery entail some energy losses (as heat energy.) To the extent that you don't have to take power from the battery to precondition it makes sense to do so while plugged in. Nothing bad will happen if you choose to precondition when the Tesla Model Y is not plugged in. (Since I rarely charge at home I usually precondition my Model Y while not plugged in.)

I have noticed that when not plugged in the Tesla Model Y may forgo battery warming if the ambient temperature/battery temperature is not too cold. When the temperature drops a bit lower then the Tesla Model Y will warm the battery regardless of whether the Tesla Model Y is plugged in. I don't know if the battery warming period is abbreviated when the Tesla Model Y is not plugged in.

I have observed 10 to 15 minutes of battery warming while preconditioning and not plugged in. Later on, after charging for ~90 minutes, when I start preconditioning in cold weather the Tesla Model Y may automatically perform even more battery warming. (Scenario: Precondition at home for 10 minutes before driving, followed by a short 10 minute drive and then a 90 minute Level 2 charge. After all that time the battery may still not be warm enough to where some additional battery warming is not indicated, performed (about 10 minutes of additional battery warming.) I have observed this happening at (~20F/-7C) so not particularly cold weather.

 

[E90alex]

Excellent - I appreciate your insights. I live in VT and it is often below 32F. I also live at the top of a mountain and going down without preconditioning results in a lot of braking if things are not preconditioned - so I try to precondition a lot in the winter.

I am mostly trying to accomplish having a warm enough battery so the regen works. From where I am up in the hills, it can take 15-20 minutes of driving until the regen kicks in, and I much prefer to drive with it working (just preference). Warming up the cabin is not so much a big deal. The seat and steering wheel warmers do a good job.

My original question mostly was about preheating with the car plugged in or not. Is it better for the battery to do that with the car plugged in or not, or does it not matter.

I wish Car Talk was still on the air. This would have been a perfect question where the girlfriend calls in and says that her boyfriend tells her that it is better to precondition the car with it plugged in, and the girlfriend wonders why this is so. (As this is the situation

If you’re not already, set the car to finish charging right before you leave if you leave at a set time every day. That way the battery is already warm from the charging and it would only need very minimal preconditioning if any.

But it makes no difference to the health of the battery to precondition while plugged in or not. It’s just more efficient to do it while plugged in. Assuming your car is plugged in anyways from charging, there is zero need to go unplug it and then start preconditioning. Just leave it plugged in.

 

[LoudMusic]

It very much depends on where you live, but when people ask me how much it costs to charge my Tesla I have two responses - I usually give them both. The super technical mathematical response comparing $$/mile of my Tesla to my mom's Honda, and stating "It's so cheap I don't even pay attention. How much do you pay for electricity? I bet you don't even know. That's how cheap it is. You just set your home air condition to whatever temperature you want and pay the bill at the end of the month."

Plug your car in and use all the features that make it enjoyable. That's how EVs are supposed to work.

 

[VT Tessie]

It very much depends on where you live, but when people ask me how much it costs to charge my Tesla I have two responses - I usually give them both. The super technical mathematical response comparing $$/mile of my Tesla to my mom's Honda, and stating "It's so cheap I don't even pay attention. How much do you pay for electricity? I bet you don't even know. That's how cheap it is. You just set your home air condition to whatever temperature you want and pay the bill at the end of the month."

Plug your car in and use all the features that make it enjoyable. That's how EVs are supposed to work.

It't not about the cost of the electricity. I was told that if it is plugged in, the car and battery are warming from the power coming in, not from the battery, thereby reducing the usage of the battery and increasing the life of the battery....... This explanation did not make sense to me and I am questioning it as hogwash

 

[LoudMusic]

It't not about the cost of the electricity. I was told that if it is plugged in, the car and battery are warming from the power coming in, not from the battery, thereby reducing the usage of the battery and increasing the life of the battery....... This explanation did not make sense to me and I am questioning it as hogwash

What part did you not understand?

 

[Eric33432]

With the Tessie plugged in and charged, turn on pre-conditioning and watch the wall or mobile connector. If the connector turns on (turns green) then it is pulling from shore power. If it does not, it is pulling from the battery.

The Tesla Energy App will admonish you to keep the car plugged in in order to conserve the battery.

 

[jcanoe]

Depending on the maximum charging power (kW) available when using Level 1 or Level 2 charging while plugged in and depending on the power required for preconditioning and possibly battery warming the Tesla Model Y can pull shore power and can also pull additional power from the battery at the same time.

 

[VT Tessie]

What part did you not understand?

When the car is not plugged in, the heatpump runs from the power provided by the battery. When it is plugged in, is the heatpump somehow powered by the electricity coming in (bypassing the power typically supplied by the battery)? I can only envision that the heatpump has wiring that provides it with energy from the battery, not two wires providing it with electricity from two sources.

 

[tga]

When the car is not plugged in, the heatpump runs from the power provided by the battery. When it is plugged in, is the heatpump somehow powered by the electricity coming in (bypassing the power typically supplied by the battery)? I can only envision that the heatpump has wiring that provides it with energy from the battery, not two wires providing it with electricity from two sources.

There is only one power feed to the heatpump (400V HVDC). The battery, charger output, and heatpump (along with motor, DC-DC converter and other HV loads) are all connected together. When the car is preconditioned without being plugged in, power is drawn from the battery. When plugged in, the car will power up the charger to power the HV bus without needing to draw power from the battery.

 

[tga]

Excellent - I appreciate your insights. I live in VT and it is often below 32F. I also live at the top of a mountain and going down without preconditioning results in a lot of braking if things are not preconditioned - so I try to precondition a lot in the winter.

I am mostly trying to accomplish having a warm enough battery so the regen works. From where I am up in the hills, it can take 15-20 minutes of driving until the regen kicks in, and I much prefer to drive with it working (just preference). Warming up the cabin is not so much a big deal. The seat and steering wheel warmers do a good job.

I live across the river on top of a hill (not worthy of "mountain"), so I'm in a similar situation.

Short answer: if your goal is to use one-pedal driving on the way down the mountain, enable "Apply breaks when regenerative breaking is limited" (pedals & steering menu), precondition to warm the cabin on shore power (to preserve range) and don't worry about it. I do this and use preconditioning for my comfort, not the battery's. Daily use of the friction brakes is probably a good thing anyway (see below).

My original question mostly was about preheating with the car plugged in or not. Is it better for the battery to do that with the car plugged in or not, or does it not matter.

It doesn't really matter. Plugged in means using shore power, no (minor) range loss, no (minor) battery cycling. Not plugged in means using battery power to precondition, some range loss, some minor additional cycling of the battery. Drawing power from the battery also warms it due to the internal resistance of the battery, so maybe fewer kWh's used, but batteries are not 100% efficient, so more kWh's have to be put back into the battery to replace the (fewer) kWh's used.

Furthermore, if you have regen available, you're converting potential energy into stored electrical energy on the way down, but you had to use electrical energy (whether from the battery or grid) to warm the battery beforehand? Did you use more power warming the battery then you recovered with regen?

All of this is almost impossible to quantify, so I wouldn't think about it. There's too many variables (pack temp, outside temp, etc, etc).

You can also argue that it's better to use a little bit of friction braking in the decent down the hill anyway - this will scuff off any surface rust and keep your rotors clean and help prevent rust pitting, and may actually extend the life of your friction brakes. Probably more important in the winter after the rotors get a salt water bath. My old S needed new rotors at around 120k miles, since the originals were badly rust pitted from lack of use. Too much regen braking can actually be a bad thing in the long run.

 

[VT Tessie]

There is only one power feed to the heatpump (400V HVDC). The battery, charger output, and heatpump (along with motor, DC-DC converter and other HV loads) are all connected together. When the car is preconditioned without being plugged in, power is drawn from the battery. When plugged in, the car will power up the charger to power the HV bus without needing to draw power from the battery.

This is the explanation I needed! Thank you

 

[jcanoe]

There is only one power feed to the heatpump (400V HVDC). The battery, charger output, and heatpump (along with motor, DC-DC converter and other HV loads) are all connected together. When the car is preconditioned without being plugged in, power is drawn from the battery. When plugged in, the car will power up the charger to power the HV bus without needing to draw power from the battery.

Unless the power demand exceeds the power available from the onboard charger, charging circuit. This can happen in winter even when charging at 11.5kW. The heat pump draw + the stator heating draw can exceed 11.5kW. Any additional power needed has to come from the battery.