Real Concern or Marginal Case Blown Out of Proportion?The Tesla Roadster 'Brick' saga continues, and more facts are coming to the surface, so let's take a closer look. It all started with this blog post which claims that Tesla's electric vehicles - the Roadster, but also the upcoming Model S and Model X - can easily be turned into unmovable 'bricks' is inadvertently allowed to fully discharge. "The only known remedy," they write, "is for the owner to pay Tesla approximately $40,000 to replace the entire battery."
Contained in that blog post is the following central anecdote:
The 340th Tesla Roadster produced went to a customer in Santa Barbara, California. In 2011, he took his Roadster out for a drive and then parked it in a temporary garage while his home was being renovated. Lacking a built-in Tesla charger or a convenient power outlet, he left the car unplugged. Six weeks later his car was dead. It took four men two hours to drag the 2,700-pound Roadster onto a flatbed truck so that it could be shipped to Tesla’s Los Angeles area service center, all at the owner’s expense. A service manager then informed him that “it’s a brick” and that the battery would cost approximately $40,000 to replace. He was further told that this was a special “friends and family” price, strongly implying that Tesla generally charges more.
It turns out that this mirrors pretty closely a letter that was sent to Tesla Motors, where the owner of Roadster #340 writes:
I love my Roadster (#340, 13K miles) and have deposits down on Models S and X. [...] As I mentioned briefly at the party, my Roadster battery is dead and unrecoverable. I had left the car unplugged for just over two months. I had no idea I was putting the car at risk or obviously I would not be in the position I am in now. I am not in idiot. I moved into a short-term rental during my remodel and didn’t have a convenient place to plug in my Roadster. I parked it in my temporary garage and planned to drive it once I was back home with my HPC.
Notice how the first version says "six weeks" but the letter to Tesla says "over two months". In the blog post it also says that he took it for a drive and then stored it, while in the letter it says that there's 13k miles on it. It's not clear which version is accurate, but it does seem like the public blog post tries to make things appear worse.
As our friends at Green Car Reports point out, Tesla says at least 4 times in the Roadster's manual and in warranty paper that the cars must stay plugged in and not be allowed to fully discharge, and the Tesla cars themselves give warnings when their charge is getting too low.
Tesla released this statement: All automobiles require some level of owner care. For example, combustion vehicles require regular oil changes or the engine will be destroyed. Electric vehicles should be plugged in and charging when not in use for maximum performance. All batteries are subject to damage if the charge is kept at zero for long periods of time.
There are also technical fixes for this problem that can make it very very unlikely to happen. For example, Nissan claims that its LEAF has a failsafe system that will prevent the battery from completely discharging. Maybe it wouldn't work if the car was stored with a nearly empty battery for months and months, but it almost all normal cases, it should work as designed.
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 8,000 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 8,000 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.
I think the bottom line is that it's possible to damage electric cars, just like it's possible to damage gasoline or diesel cars, if you do things that you're not supposed to do. They are designed to take a lot of abuse and protect people from mistakes, but it'll always be possible to do something that causes damage. Tesla finds itself in a delicate position because if they just repair and exchange batteries for free in cases where Tesla owners did things they were warned not to do, they would just be encouraging Tesla owners to 'brick' their cars whenever they feel like having a new battery pack for free.