# The cost of battery pre-conditioning



## GDN (Oct 30, 2017)

Stick with the story here - I'll get to pre-conditioning. A weird sequence of events this evening. I thought I had lost my wallet and we made a couple of trips out to the car as we searched, so the doors were opened and closed a couple of times. The wallet was found inside the house and we left with a friend in his car to dinner. Returned home about an hour and half later, about 8:20 and could hear the car in the garage roaring away. As others have noted it sounded like it was preparing for take off. Noticed right away even the garage was hotter than it was outside. I unlocked, then opened/closed the door and it quit.

Checked on the car in Teslafi and it shows the battery had started pre-conditioning the battery at the time we had been in it looking. The time frame in Teslafi isn't 100% - we returned home about 8:20. So for an hour and a half the car was pre-conditioning the battery for super charging. I have no idea what put it in that mode or why it continued so long knowing it wasn't going anywhere. It took 20% of the battery and almost 50 miles of range. It was generating enough heat that the temperature in the car and in the garage went up 8 degrees, so indeed pre-conditioning does work, but at a pretty good cost of energy.


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## JasonF (Oct 26, 2018)

If you have the car set to automatically start directions to some destination when you wake it up, that might trigger battery pre-conditioning.


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## GDN (Oct 30, 2017)

The only place is still each day if I drive before 11 or so it will want to give me directions to work - but no one touched or opened the screen or charging to my knowledge.


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## Bigriver (Jan 26, 2018)

I have some data to contribute about the cost of battery pre-conditioning for my 2018 model 3. The tl;dr version is that I estimate it costs about 30 rated miles, which at about 240 Wh/mile and $0.34/kWh at an Ohio supercharger is $2.45 out of pocket.

I arrive at that and validate it as a reasonable estimate through several different aspects of a recent trip. I took the model 3 instead of the model X on a trip I do at least monthly. 

I was hoping to make it to a supercharger that is 225 miles away. With my rated range currently at 295 miles at 100% SOC, I needed to get 76% actual miles/rated miles. My historical data from Teslafi tells me I have averaged about 80% for winter temps. To help improve my odds, I put on the butt-ugly aero wheel covers that haven't been used since the car arrived home over 3 years ago. I put air pressure at 45 psi. I charged to 100%. I set my autopilot speed to 73 mph. The arrival estimate for the SC was as high as 12% at one time, but as it was settling on 5% I decided to do a quick SC stop as an insurance policy. It was exactly on the route and a quick biological break was sounding good too. So I did one of the fastest pit stops ever, adding 10% SOC. When I got to the originally planned SC, I was at 4% SOC. It felt like the car threw me under the bus and used the entire extra 10% that was supposed to be margin. The preconditioning message had been on for over 30 min, and I watched the estimate SOC at destination drop steadily. So my rough estimate is that the 10% extra SC session got used to precondition, and that is equal to about 30 rated miles.
On the return trip, my first trip segment was 155 miles to the SC. The battery conditioning message was again on for a long time. If I get my usual winter efficiency of 80%, I should have used 194 rated miles. But I used 224 rated miles. Again, a 30 mile delta.
In the final 2 trip segments, I didn't route to a supercharger. I did one more SC stop, but I entered its address instead. In both of these segments, I got 85% actual miles/rated miles. I think this validates that 80% was a reasonably minimal estimate for my current car condition that I should have achieved in my earlier segment.
For the cost of $2.45 per battery preconditioning, I did get phenomenal charging rates. It will stick in my memory for quite some time that I went from 4% to 90% SOC in 32 minutes. In the winter. But I am somewhat taken aback by the cost in the loss of range, more so than the dollar cost. And I also didn't need that fast of a charging session. I typically have a number of things I need/want to do when I stop and another 10 to 15 minutes is not a bad thing for me. So in the future, I will consider it an option to navigate to the SC address rather than navigating to it as a charger.

Another commentary is that the navigation estimates did not seem to account for what would be used by battery preconditioning. I think I drive more conservatively than most Tesla drivers, and I am used to the estimated SOC at my destination increasing as I drive. This is exactly what happened on my last 2 trip segments when a SC was not set as the destination. But the estimate at arrival continually decreased with the battery conditioning with the SC set as the destination. It was quite a dramatic change on the 155 mile segment. It was originally estimating 28% but actual arrival was at 14% SOC. I have never had that bad of a miss in the estimate. Again, this is a route I travel all the time and there was nothing unusual in the conditions or how I drove.

Here is my Teslafi historical efficiency vs ambient temperature for trip segments over 100 miles. Note that most of this was generated before the battery conditioning became a thing, or are more local trip segments that didn't include navigating to a supercharger.


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