Recently, the NHTSA tested the Chevy Volt and, to the surprise of journalists everywhere, found that occasionally, the battery can catch fire.
Forgive me, I suppose I should be shocked by this revelation. A car you say? Catch fire you say? After a wreck? What have GM’s engineer wrought upon this Earth? Oh, the humanity!
Really, it shouldn’t be surprising to anyone that a wrecked car can, occasionally, catch fire. Hollywood theatrics aside, it can and sometimes does happen with gusto. Here’s the thing, unless you are in the habit of keeping your tank absolutely full all of the time, you are usually riding around with about some pretty volatile gasoline vapor in your car’s fuel tank. Gasoline vapor explodes, violently, when exposed to an ignition source. It is this explosive tendency that is exploited to provide power to move the car via the pistons and drivetrain.
More generally though, what you are really riding around with is energy. In the case of a typical car with a 12 gallon gas tank, that’s about a billion and a half joules of energy, the energy equivalent to 1,560 candy bars. Another way to think of it: if you converted all of that gasoline in to energy in one-second, you would have generated 1.5 gigawatts of power, slightly more than is required to send a DeLorean 30 years back in time.
Fundamentally, there isn’t any difference between a gas tank and a battery. Before you flip out and point out the obvious (“Zach, a battery is a battery and a gas tank is a gas tank…duh”), what I mean is, both a battery and a gas tank are energy reservoirs. Unlike gas in a gas tank, electricity from a battery cannot come out and slosh all over everything if the battery is ruptured.
In a Chevy Volt, you have both a battery and a gas tank. The electricity for moving the car comes from a Lithium Ion Polymer (LiPo) 16 kilowatt-hour 379lb beast of, what is essentially, a cell phone battery. It does have a cooling system, but, it is present more to extend battery health and even charge distribution than to actually cool the battery. Getting back to our energy reservoir analogy. The battery, at full charge, contains enough energy to provide 16 kilowatts of power for one hour. In practice, the software limits the available power to 10.4 kilowatt hours but we’re going to assume that the software unable to control the battery in a crash. Now, lets also make another assumption; that the battery can discharge all of it’s power in one second, something it cannot, in reality-land, actually do. If we consumed all of that energy in that one second we mentioned earlier, we would have 57.6 megawatts of power; about 30 times LESS energy than is contained in an average gas tank. As I said, in reality, batteries do not work this way and you cannot extract all of the available power from a battery in one second. Gasoline does work this way. If you vaporize 12 gallons of gasoline then ignite it, I hope you have your affairs in order.
What I am really getting at, and what I think is at the heart of all of this hype and hysteria, is a familiar fear that we’ve all had and probably still have about electricity. You see, if I spill some gas, I can run away from that gas and be relatively safe. I can see or smell where the gasoline is and, if I can at all help it, stay away from it. Electricity can’t be smelled, tasted, or seen pouring out of a battery. A damaged battery can look just like an undamaged one and may even work properly. Furthermore, even though batteries have powered forklifts and other specialty vehicles for decades, for the consumer, a battery powered vehicle is a very recent development. People hear electricity and think instant death, especially at the power levels required to run a car. Electricity, or more appropriately, the lack of understanding about the nature of electricity and batteries, is nightmare fuel indeed.
Now about the NHTSA testing. It was found that after a 20mph side pole impact, the battery caught fire some time later damaging some cars near where it was towed after the crash. Let’s examine this for a moment and break it down a little bit:
1) The car was wrecked.
2) The wrecked car was towed to a storage lot.
3) Two weeks later it caught fire.
This is not typical of how a Volt wreck (or any car wreck) would be handled. No one (that I can think of), after being involved in a side impact at 20mph is going to drive home and let their car sit for two weeks. The car would be towed to a Chevy dealer where, as a matter of Volt protocol, the battery would be checked for damage. Insurance would typically cover the cost of repairs and a loaner vehicle and you’d be back on the road with, most likely, a new battery in your repaired Volt.
Sometimes it is important to note what didn’t happen rather than what did. What didn’t happen is a battery explosion. What also didn’t happen is a horrifying electrocution of anyone involved with the test. After scouring the interwebz, I could only find -two- fires involving a Volt. One fire was determined to be unrelated to the volt leaving the other fire as the single…unexplained…incident. Read UNEXPLAINED, meaning not directly attributable to anything which certainly doesn’t implicate the Volt necessarily.
The other Volt testing related fires unfolded in the same way. The car was thoroughly abused and then left alone resulting in a fire. One was rolled over and in the other the battery was punctured. In both cases, were this to happen to a consumer, neither car would be back in the owners garage at the end of the week.
So in the end, is the Volt safe? Yes. It makes a great story when you read that GM with all of it’s recent troubles has made a car with a propensity to catch fire. It is particularly juicy to read that the car in question is the much hyped Chevy Volt. But when you remove all of the drama and compare the technology in the Volt to traditional car technology, there really isn’t much of a story at all. Like the mess with the Toyota Prius and it’s supposed tendency to go on an uncontrolled freeway rampage, this is an inflated situation at best.
Am I wrong? Possibly. However, next time you roll your car or sideswipe a pole at 20mph, go ahead and forgo the tow truck, drive your car home, and then report on your findings. I’d love to hear it.