Interview With Elon Musk On Tesla Model S Performance In Cold Weather
Ovidiu Sandru of The Green Optimistic recently conducted an email interview with Tesla Motors Founder and CEO Elon Musk regarding the Tesla Model S and how it performs in cold weather. Reposted from The Green Optimistic, here’s a compiled summary of the interview:
Ovidiu: How does the Model S manage cold weather? As far as I know, the Roadster had auxiliary battery heating systems and for sure the Model S has them, too.
Elon: The rough answer is that range drops about 10% in the sort of weather seen during the NYT test drive, but this is primarily due to energy being directed towards cabin heating.
Ovidiu: What is the energy spent (per hour) to warm up the batteries to the chosen temperature, even in subzero conditions?
Elon: The battery actually loses very little energy when cold. Keeping batteries cold is actually the best way to preserve them! It only loses energy when keeping the pack warm for the convenience of the driver — so you don’t have to wait long to drive.
Ovidiu: Is this an active system that prevents battery failure due to extremely low temperatures, even if the car is not being used?
Elon: Once you start driving the liquid thermal loop transfers heat from the motor, gearbox and inverter to the battery pack, so not much incremental energy is needed at that point. We also close the radiator louvers at the front of the car (which has the dual benefit of lowering drag) and close the valve leading to the radiators, so the liquid loop doesn’t reject energy to the environment.
Ovidiu: I was wondering: couldn’t you use an ultracapacitor as a buffer between the battery and the motor, for the gearbox/inverter to do their heating thing while the user has a satisfying performance from the very first second, without waiting for the battery warm-up? That would be even nicer than in ICEs, because the ultracapacitor would hold its discharging performance even in low temperatures.
Elon: Ultracaps are actually what I was going to do my Phd on at Stanford, so I’m a big fan. I think we could see a breakthrough there in the next few years. Energy density from current tech is too lame to bother.
To have Elon Musk even think about ultracapacitors is a good thing. He doesn’t believe in hydrogen for cars, but to hear that he’s a “big fan” of ultracaps right from the man himself – that message means something for the future of the car industry.
With Musk and the Tesla Model S leading the wave, the future of electric cars will be bright, for sure.
Thanks, Elon!
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Thanks for thr post Zach. I really liked Elons’ answers. Especially to the question of the Ultra Capacitor use. I do believe he is correct in the development of better capacitors within the next few years from what I have been reading in the R&D mags; and seeing in DOE and ARPA-e works done. This will be an exciting area.
Excited to see them move forward.
Actually I didn’t like Elon’s answers. They were vague and or elusive. For example:
“Ovidiu: What is the energy spent (per hour) to warm up the batteries to the chosen temperature, even in subzero conditions?
Elon: The battery actually loses very little energy when cold. Keeping batteries cold is actually the best way to preserve them! It only loses energy when keeping the pack warm for the convenience of the driver — so you don’t have to wait long to drive.”
WTF Elon? Tell them how many watts per hour are used in the conditions that con man at the NYT was experiencing! Better yet give a number and refer us to a graph showing us all the conditions tested.
My personal experience with hybrids and plug in hybrids tells a different story with winter performance of the batteries. Both nickel metal hybrid and lithium ion batteries, there is more than a 10% efficiency hit in cold weather driving. My personal experience is with both a 2004 and 2005 Prius with factory hybrid battery, the same 2005 with a Hymotion L5 after market Nanophosphate Lithium Ion plug in battery pack, 2010 Prius, 2012 Plug in Prius and 2013 Ford CMAX Energi.
The regular hybrid Prius’ gas mileage goes from 56Mpg in summer months to 49Mpg in winter months – a 12.5% hit. The plug in after model Prius goes from 75+Mpg to 47Mpg, a 37% hit. The CMAX was purchased in the end of November so we don’t have an warm month driving experience yet. My experience is batteries dont perform better in the cold. They may like the colder temperatures, they just don’t maximize their efficiency in colder temperatures.
Does the Prius have a system for warming the batteries like the Tesla?
The Tesla batteries may start cold, but they don’t stay that way.