A blog posting
recently made the rounds regarding a fatal design flaw in the Tesla
Roadster. The blogger claims that some Roadsters have become “bricks”,
with non-functioning batteries requiring a $40,000 fix. The blog is dead
wrong about most of the technical facts it claims to be reporting.
Don’t blame the blogger, however: he’s only participating in a trend of
misinformation about electric vehicles that is starting to impact the
reputation of the fledgling industry.
Here’s the primary fact that the blogger in question doesn’t
understand: the Tesla battery pack is not a battery. It’s a collection
of more than 6,800 individual batteries. Each of those cells is
independently managed. So there’s only two ways for the entire battery
pack to fail. The first is if all 6,800 cells individually fail (highly
unlikely except in the case of something catastrophic like a fire). The
second failure mechanism is if the battery management system tells the
pack to shut down because it has detected a dangerous situation, such as
an extremely low depth of discharge. If that’s the case, all that needs
to be done is to tow the vehicle to a charger, recharge the batteries
and then reboot the battery management system. This is the most likely
explanation for the five “bricks” that the blogger claims to have heard
about. They probably aren’t actually bricks, but cars in need of
servicing.
Another error on the part of the blogger is the claim that if the
cars discharge fully, the battery packs will be damaged. This is
blatantly false. The battery management system of the Tesla Roadster
keeps the battery from being discharged to a damagingly low state of
charge under normal driving conditions. It’s true that a full discharge
to zero percent state of charge can potentially be damaging to a
battery. However the battery management system of the Roadster won’t
allow the car to reach that low level of charge.
There is a fundamental problem when any rechargeable battery is
discharged and then left to sit for months. Any boat owner understands
that that’s why you plug in a trickle charger when the craft is put into
storage. The same should be done for any electric vehicle. However, to
imply that the Tesla Roadster has a fundamental design flaw because of
the nature of electrochemistry is like saying that Chrysler has a
fundamental design flaw because its engines will be damaged if you drain
all the oil out and then drive cross-country.
The blogger in question is, unfortunately, not a single voice in the
wilderness. He’s part of a widespread trend throughout some parts of the
blogosphere and some parts of traditional media to politicize and
demonize the electric vehicle. This trend has in turn damaged the
general reputation of the automakers taking risks in building and
selling these vehicles. This isn’t the only problem that electric
vehicles have today (overpricing and bad choreography have done their damage too). But there’s an antidote for this type of misinformation: confronting it with facts.