Tesla’s Musk disses the Volt

The CEO of Tesla spoke recently about why the Volt’s electric-gas serial hybrid configuration was a worst of both worlds configuration, and why the pure EV holds an advantage over the hybrids of the world. Talking trash or substantive discussion?

Perhaps the most pertinent technical quote is the following…

An important consideration that people without a technical background don’t understand is that you can either have a high power or a high energy cell chemistry, but not both. Since the battery pack in a plug in hybrid like the Volt has to generate the same *power* as a much larger battery pack in a pure electric vehicle, it has to use a low energy cell chemistry.

This is true, and it explains why the Volt’s battery pack is both larger and heavier than proportions might expect – the Tesla Roadster battery pack is about 1,000lbs, while the Volt’s is estimated to be about 400lbs. So instead of the Volt having 20% of the range and 20% of the battery weight of the Tesla, it has 20% of the range and 40% of the weight.

With Tesla’s battery pack, you pull a smaller amount of power from each Li-Ion cell, where as the Volt has fewer cells, the power load is spread out amongst fewer cells so each cell has to generate more power. Musk states that the battery chemistry must adapt to be able to provide that much power, and it results in a lower energy density – resulting in higher volume and weight. Given that battery chemistry is pretty much always a trade-off, there isn’t much you can do about it. If there were a “perfect chemistry” with respect to price, manufacturing, energy density and power, we wouldn’t be having this discussion.

Though what Mr. Musk doesn’t address is that at some point, we reach the ceiling for vehicle performance – going to 0 to 60 in 6 seconds for a standard sedan is great, and at some point, the average consumer isn’t really demanding more performance from their vehicle. As chemistry improves, cells will be able to deliver the necessary power and with today’s maximum energy density, as the recent innovation in LiFePO4 batteries demonstrates, overall cell performance will improve as we move into the future. While the pure EV will always be ahead from a spec sheet standpoint, in a practical sense there will be a limit as to how fast you can make a sports car: tire traction limits, 0-60 in 1 second is about 3Gs (which is a lot, but its not sustained, rather over a short period of time; I’ve been on the Mission: SPACE ride at Epcot Center in Florida, and that was a sustained 2.5Gs and that was pretty intense, and there have been two deaths on the ride associated with pre-existing conditions).

While Musk’s comments are very relavant now, it is unlikely that they will be relavant for the life of electric vehicles – within 10 or 15 years it is entirely likely that all PHEVs offer custom ranges (25, 50, 75 miles) and have the necessary power and charge cycle capacity to satisfy the 10 year/100,000 mile warranty required by law. Meanwhile, the more pressing problem for the future of Tesla is recharging pure EVs as quickly as you can fill a tank of gas today. The large amounts of current (480V/1,125A) needed to recharge a 160mi Model S in five minutes is prohibitive.