Running heater while pluggen into charger

Running heater while pluggen into charger

One thing that got me really exited about Tesla S is the fact that via an app I could start the heater and get out into an nice warm vehicle. No stress getting frost and ice covered windwos clean. Just sit 5 more minutes at the breakfast table sipping hot coffee waiting for the heater to clean all windows.

To my surprise I discover that even when plugged in to a charger heating the car before driving will actually drain power from the batteries rather from grid. Why is that? Does it even make sense to drain battery power heating the car as long as the car is connected to the power grid? Why not just drain power for the grid to heat the car - that way you can squeeze a little extra driving range from the batteries.

Also I have read that Tesla has developed some smart software that manage the charging process. Always taking care of of batteries durability to maximize battery life. Yet reading this forum it seems people are not too sure about this software. Is there any glitches or have people found it to be faulty? What is the best way to care properly for the Tesla? Park it as much as possible plugged in to the grid? What if I go to travel and stay away for 2 weeks. Can the car stay plugged in all that time without "cooking" the batteries - or does the smart software regulate so well it is not even a problem?

Brian H | 27 janvier 2013

Currently cabin heating while charging cannot be done with no one in the car. That will change with the scheduling s/w.

wolders | 27 janvier 2013

I leave the drivers door slightly ajar as a work around to get the interior from - 25 celsius to 17 celsius.

Every thing in the car that uses electricity accept the drive motor should preferentially choose the grid, when and if there is an adequate power source available over the internal battery.


TS | 27 janvier 2013

It has been between -5 and +28 degrees Farenheit in Oslo for the last weeks , and its normal from november to march.
I really expect Tesla to launch a preheating function that works both plugged and unplugged, before they start deliveries to Norway (the second biggest marked for this cars in the world)

Or else it would be necessary to install a Webasto or Ebersprächer heater. (I dont want that smell...
and I would get a bad feeling when filling diesel or gasoline into this premium EV. )

I also expect to see official longterm testresults from this kind of climate and topography before I buy it.
A local Toyota salesrep told me that they dont believe the Rav4 EV (built by TM) could be sold or used in our climate and topography.

But for now, I really appreciate the feedback from the american owners with simular climate.

I know that somebody in TM actually is thinking of us here in the north, beacause when I discussed useless "all year" tires with a rep at the local TM showroom, another rep suddenly came out and said that they just decided to offer "real" winter tires.

One example of "non working batteryopreated device" over here, is iPhone. When we take them out of my pockets in cold weather to send a message or take a picture, it dies an tell us to charge. Even if it has 80% battery left. (This is not the right thread for mobiledevices, so please dont comment this..)

torst1 | 27 janvier 2013

@Brian H
Running the heater can not be done without anyone in the car? Why?
Is that a software glitch or some lame security issue?

As I see it is a must to able to heat Tesla s while plugged in. And 1 must be able to start the heater from a smartphone - sitting at the table sipping coffee.

Slightly different topic that I feel must be addressed is the problem that the batteries does not stay warn while plugged in. Why is that? Unplugging the car and drive off in the morning the first thing cars does is drawing extra power from the batteries to heat up the batteries - while eating away the drive range? Why not just keep the batteries heated while plugged in?

Brian H | 28 janvier 2013

It's just not implemented yet.

torst1 | 28 janvier 2013

Ok - so it is possible to heat car from grid while plugged in - it is just not implemented yet. Good.

What about the heating the batteries? Will that also be possible to do while plugged into to grid? Preferable from your smartphone while eating breakfast and drinking coffee?

Brian H | 28 janvier 2013

Already possible, indirectly. Charge at very low rate leading up to use. Not from mobile yet. Charge all night at low enough rate that it's not quite "done" in the morning.

edcalis | 28 janvier 2013

I have a Volt, waiting to get an S. The Volt can be heated in advance through the OnStar Application. No problem there. The only thing is that like the initiator of the thread said, the power is being drawn in the Volt from the batteries and not directly from the grid, for some strange reason.

Timo | 28 janvier 2013

@edcalis, power is being drawn in the Volt from the batteries and not directly from the grid

That would be the case with Model S as well. There just is no direct connection to onboard systems from grid, only chargers are directly connected to it. Of course using batteries while it is charging is possible just like with mobile phones.

jkirkebo | 28 janvier 2013

Same with the Leaf. You can heat the car from the app, and it will draw power from the grid. However the heater is of course on battery voltage and so it draws from the battery while the charger charges the battery. Since the heater is 5kW and the charger is 3.3kW, pre-heating my car usually draws the battery down some, but much less than if I heat the car while not connected to the grid.

The Model S will of course be the same, as the heater(s) cannot operate on 120/240V but needs the 365V DC from the battery. So it is simply a programming issue to use only grid power. The heaters must then not use more power than the charger can supply. If you have a 14-50 the heaters must limit to 9.6kW. This should be settable, ie. either use heating at full power or limit to grid power capacity. If you choose the latter and have only a 120V connection heating will however take a _long_ time.

If you have enough grid capacity (like a HPWC) you could heat & (range)charge at the same time. This should be separate options in the app, like "heat", "heat&charge" and "charge". Choosing "charge" would of course also heat the battery but not the cabin. With two-way communication the "heat&charge" button could be disabled if the grid connection cannot support both at the same time.

jat | 28 janvier 2013

@torst1 - the batteries are automatically heated as necessary to prevent damage. After the car is fully charged, it periodically wakes up and recharges the battery for what has been used heating the battery. You can see a graph of the energy use at

As far as heating the battery to full operating temperature rather than just enough to prevent damage, I haven't heard of anything like that but my guess is it would be possible in a future software update.

Dr. Bob Reinke | 28 janvier 2013

I often use the grid to heat my P85 Sig. At my resort the car is parked outside and -0 temps in the morning are normal in winter. Normally, I can also heat the battery by limiting the charge on the touch screen to 10A so the charge remains on for an extended time. @wolders mentioned above, I set the desired heat and charge rate and after getting out of the car, I close the drivers door to the first snap, and the car believes it is still occupied.(not recommended where the car is on the street) The heater continues until I disconnect, and drive away in a warm car with a fully activated battery.