I'd like to come back on the excessive loss of charge of the battery in the cold (reported to be 12 - 31 miles per day vs 1% or 3 miles per day as per spec)
I have been seeing a loss of 50 miles in a 24 h period while being on call. The car war parked outisde, no outlet available. Temperatures dropped to the 20s overnight. The following is a repost from the TM General forum.
Ok, here is some real world experience from three weeks of daily driving my P85 in the DC area.
- You will use more energy on cold days. Cabin heat and battery pack heating use the most. Temperatures here have been in the 20s at night and 30-40F during the day. With that my average consumption has been 400 WH/mile. Not too bad but you will not get your rated mileage. When there is snow on the road this will get even worse. (Real energy usage is probably a lot higher. This reported number from the trip logs might use only the energy USED, not what you actually put in (and pay for...) the battery
- The battery pack DOES care about its temperature and is actively controlled. When it gets cold it will heat the pack and that uses energy. This may not be a problem if you are plugged in but needs to be taken into account when you leave your car in the cold unplugged (airport, work, etc.). When I left my car outside for 24h with temperatures ranging from low 40s to 20s I had 50 (rated) miles less the next morning. (That is with the newest 4.1 firmware and sleep mode enabled.) It still works for me because my commute is 80 miles but keep this number in mind when choosing your battery pack! As soon as battery heating is involved you will not be even close to the published 1% LOC per day but much greater.
- If you live in a cold climate go for the largest battery even if that means skipping options. In my experience so far I think the 40kwh battery is not going to be a viable option unless you can plug in your car whenever it is parked, ALL THE TIME.
------Chris DC | JANUARY 12, 2013
Well it is clear that loosing a lot of charge overnight in cold temperatures when the car is not plugged in is not an isolated event. I am sure Tesla has reasons why they keep the battery pack temperature more controlled than other manufacturers (i.e. Nissan Leaf). My guess is that they want to ensure energy deliverance even at cold temperatures. LiOn batteries do not work well when cold.
The problem I am having with this is that this has not been communicated by TM with full disclosure. The only official statement I can find is a 1% LOC per day (manual) and that the car can be left for months not plugged in and will not suffer damage (plug it in blog).
Although I agree that the Model S should be plugged in when parked we all have to realize that in real world conditions this is not always possible. When you have your car you will realize that for example not all airport parking will have working outlets available or (in my case) parking garages usually do not have accessible outlets either. Loosing 50 miles in a day when I am on a 24h shift is a lot in my opinion.
I am predicting some upset owners of the 40khw model S once that gets delivered. They WILL leave their car unplugged at times and will not be able do drive it the next day, at least in the winter. TM needs to be more open about this so people can have realistic expectations what the Model S can and cannot do.
