Monday, September 21, 2009

Turning Up The Heat

Now that the summer is gone and temperatures are dropping here in New Jersey one question is on the minds of the East Coast MINI-E drivers: How much energy will the heaters in our cars consume and how will it effect our range? Now I know the California pioneers are snickering at us here in NJ & NY as this will not be a concern for them, but we will have to live with a reduced range here, there's no way around it. I believe this is the reason MINI decided to bring the program to the East Coast instead of just California like most EV programs are limited to. I think this fact alone proves MINI/BMW really is serious about this field trial and wants to collect as much data possible. It would have been much easier for them to run this program in CA only, but they would not get the cold weather data that they will now. I have used the heater a couple times already in the past two weeks and I was actually quite worried with the results. It seemed that my range was really taking a beating (15-20%!) from using the heater. I say "seemed" because it was a very small sample and done completely unscientifically, with many other uncontrolled variables like speed and driving conditions. Plus, the range indicator in the car really isn't close to being exact, and the faster you drive the less accurate it gets. Only after you slow down or stop for a while do you get an accurate reading. I was using the heater while I was driving 65+mph driving home at night and watched the charge meter drop like a rock and that worried me so I decided to do some testing in a controlled environment. The past three days I charged the car to 100% and then turned it on and put on the heat. I first set the heat control to the highest setting. Then I turned the fan to the highest setting for 10 minutes to simulate the initial warm up period and then lowered the fan to the lowest setting which should be how I use it most of the time. The cabin is so small the lowest setting should be all I need to maintain a warm environment. I then let it run for an additional one hour and fifty minutes. I usually drive for about two hours a day so this should be close to the energy use I will incur, except for the fact that I will have multiple "warm up" periods that may use some more energy. After the three day test the results were pretty consistent. Twice I finished with 91% charge remaining and the other time I had 92%. This experiment made me feel a lot better about the using the heater. The test shows I can expect an 8% to 9% reduction in range if I use the heater 100% of the time which I suppose won't be the case on most days. Plus, I won't have the heat setting to the highest level as I did for the testing. The only other wild card will be how the batteries react to the frigid weather we can have here in New Jersey. What will happen when it's 10 degrees outside with a wind chill below zero? I can't simulate those conditions in my garage so I guess I'll have to wait and see. You'll be the first to know.


  1. Did you ever do this same test with the air conditioning on instead of the heater? I wonder if it used as much energy.

  2. No I didn't. This summer was unusually mild and I really didn't need to use the A/C that much. At the end of August, there was a period when we had some 90+ degree days and I used the A/C a lot. I did notice a reduction, but I didn't isolate the use of the A/C to see it's true draw so my findings aren't really useful. There were days that it seemed like the A/C used a lot of energy (10 to 15%) but then other days it seemed to only use 5% more so I really can't say what the draw was. Also, on these days, the battery temp was really high (over 110 degrees) I think the high battery temp had more to do with the reduced range than the A/C use did. One thing I have learned is that proper battery temperature is critical. The Mini E is air cooled as compared to Tesla's liquid cooled system that manages the batteries temp a lot better.