Tesla Motors Club
Hello again fellow New Englanders! With the polar vortex visiting us more frequently now, I was a little surprised by just how much the energy seems to go into heating the car on short trips. I wanted to quantify this a bit with the goal of hopefully identifying some improvements. Green car reports noted that the average U.S. automobile trip length is just 6 miles, hence the focus of this study is not on vehicle range but typical energy usage in winter climate.
I ran a little designed experiment (DOE for stats fans) to study the effects of ambient temperature, pre-heating, pre-charging, and climate control on a typical short trip. I wanted to share the results in this smaller audience, and see if anyone is seeing drastically different behavior and collect your feedback.
Some comments before getting to the results:
-We have a MS60, so I expect the thermal energy required to heat the battery may be somewhat less than the MS85.
-The study varied from 4.5-9 mile trips after the vehicle was at rest for more than 4 hours.
-The trips were all on very flat terrain (no more than 40ft elevation change), with speeds less than 40mph as I didn't want drag to be much of a factor.
-I did not put the vehicle settings in "range mode" which has been reported to disable the active battery heating. Honestly, the climate control is too weak in this setting for the general public (e.g. my family members) in extreme weather.
-Anytime climate control was used, interior temperature was set to 70F.
Some general conclusions:
-Initial temperature is a huge effect. Every 10 degree F was worth 60 Wh/mile.
-Turning climate off seems to also disable the battery heating and save copious amounts of energy so long as you can stand the cold.
-Battery pre-warming via charging at 40amps did not show a significant reduction trip Wh/mile (perhaps the MS only heats the battery to ~30F for charging?)
-Preheating the interior saved an additional 111 wH/mile (although this energy is still coming from the wall).
-Energy used in heating the battery plus interior can exceed 2.2kWh for a 6 mile trip at 20F (equivalent to driving an additional 8 miles).
-I'm not hearing a heat pump running, and some rough calculations suggest that resistance heaters could be providing all of the heat.
The 3 factor linear regression equation resulting from the experiment is shown in blue text below. Climate and pre-heat are set to either 0 or 1 for calculating their effect. Whether the vehicle was charging or not did not prior to departure did not show a significant effect and was dropped from the model.
And here is the data collected over the last few weeks, with a linear regression model included.
Regards,
Sean
I ran a little designed experiment (DOE for stats fans) to study the effects of ambient temperature, pre-heating, pre-charging, and climate control on a typical short trip. I wanted to share the results in this smaller audience, and see if anyone is seeing drastically different behavior and collect your feedback.
Some comments before getting to the results:
-We have a MS60, so I expect the thermal energy required to heat the battery may be somewhat less than the MS85.
-The study varied from 4.5-9 mile trips after the vehicle was at rest for more than 4 hours.
-The trips were all on very flat terrain (no more than 40ft elevation change), with speeds less than 40mph as I didn't want drag to be much of a factor.
-I did not put the vehicle settings in "range mode" which has been reported to disable the active battery heating. Honestly, the climate control is too weak in this setting for the general public (e.g. my family members) in extreme weather.
-Anytime climate control was used, interior temperature was set to 70F.
Some general conclusions:
-Initial temperature is a huge effect. Every 10 degree F was worth 60 Wh/mile.
-Turning climate off seems to also disable the battery heating and save copious amounts of energy so long as you can stand the cold.
-Battery pre-warming via charging at 40amps did not show a significant reduction trip Wh/mile (perhaps the MS only heats the battery to ~30F for charging?)
-Preheating the interior saved an additional 111 wH/mile (although this energy is still coming from the wall).
-Energy used in heating the battery plus interior can exceed 2.2kWh for a 6 mile trip at 20F (equivalent to driving an additional 8 miles).
-I'm not hearing a heat pump running, and some rough calculations suggest that resistance heaters could be providing all of the heat.
The 3 factor linear regression equation resulting from the experiment is shown in blue text below. Climate and pre-heat are set to either 0 or 1 for calculating their effect. Whether the vehicle was charging or not did not prior to departure did not show a significant effect and was dropped from the model.
And here is the data collected over the last few weeks, with a linear regression model included.
Regards,
Sean