Elon Musk Interview: How Model S Manages Cold Weather

Now that the New York Times scandal is over, I interviewed Elon Musk about some technical facts on how the Tesla Model S handles cold weather and how it could be improved to maximize mileage per charge.

For those who are new to the topic, Elon Musk is the man behind Tesla Motors and SpaceX, NASA’s, for the moment, only chance of going to space, and the co-founder of PayPal. His dreams are big: getting to Mars in his lifetime and having each car on Earth become electric. And he’s made some impressive steps so far.

Elon is also the brightest mind behind the electric Model S that’s been recently accused by New York Times’ John Broder of not delivering the range it promised, for almost $100k, in cold weather.

It’s been proven, eventually, that Broder didn’t use the best judgment possible when he floored the Model S or when he turned the heat up for longer than necessary. Moreover, the same trip has been since re-tested by a bunch of other journalists from CNN, CNBC, Consumer Reports and actual Model S owners, who disproved what Broder had written.

Here’s a compiled summary of our e-mail exchange since yesterday:

Me: 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.

Me: 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.

Me: 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.

Me: 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!