Federal Investigators looking into Chevy Volt after Second Battery Fire

Posted by PITHOCRATES - November 26th, 2011

Week in Review

Why did we pick gasoline to be the fuel for our cars?  It takes little special handling.  And the energy it contains is highly concentrated.  One full tank could take you hundreds of miles.  And if you ran out of gas you could walk to a gas station.  Fill up a gallon can.  Walk back to your car.  Pour it in your tank.  Drive back to the gas station.  Fill up the tank.  And travel hundreds of miles more.  Of course this rarely happens.  Because our fuel gauge is a pretty good gauge.  It usually gets us to the gas station before we run out of gas.

It’s a little different with electric cars.  The ‘fuel gauge’ tells you how much charge is remaining.  But it doesn’t really tell you how far you can go.  Because the same amount of charge will take you different distances.  Depending on what else will be on.  Will you have your headlights on?  The heater?  If so, that charge will take you far less than it would without the headlights or heater on.  And if you run out you just can’t fill up your battery.  No.  That car will be little more than one very large paperweight.  You’ll either look for ways to kill a few hours (4-6) to recharge the battery.  Or you’ll be taking alternate transportation home.  And making arrangements to tow your electric car home.

Gasoline is a perfect fuel.  It’s stable at ambient temperatures.  It doesn’t freeze.  Stores easily.  A little of it goes a long, long way.  And it’s safe.  To get that explosive energy from it to move engine pistons you first have to convert it to a vapor, mix it with air and ignite it with a spark plug.  Things that just don’t accidentally happen.  Even after an accident.

If an accident is severe enough an automatic fuel shut-off valve will close.  Keeping the gas from feeding any fires that happen to break out.  Afterward the car can be towed.  And locked safely at an impound yard.  Without the fear the gasoline will spontaneously start a fire.  Apparently not the case with a battery (see Formal Defect Inquiry of Volt Battery Begins posted 11/26/2011 on The New York Times).

Federal safety regulators on Friday said they have begun a formal defect investigation of the Chevrolet Volt because a second battery caught fire after a crash simulation.

The regulators have been examining batteries in several plug-in cars since a June fire involving a Volt that had been heavily damaged in a government crash test.

On Thursday, a Volt battery pack that was intentionally damaged Nov. 17 as part of that testing caught fire, the National Highway Traffic Safety Administration said. The agency also recorded a temporary temperature increase in another battery pack one day after it was damaged, and a third pack “began to smoke and emit sparks” after it was damaged and then turned upside down to simulate a rollover crash.

“N.H.T.S.A. is not aware of any roadway crashes that have resulted in battery-related fires in Chevy Volts or other vehicles powered by lithium-ion batteries,” it said in a statement. “However, the agency is concerned that damage to the Volt’s batteries as part of three tests that are explicitly designed to replicate real-world crash scenarios have resulted in fire.”

The key to a successful electric car is making a long-lasting battery.  One that can match the range of a gasoline engine.  Easier said than done, though.  Because gasoline and the engine are stored separately in a car until that energy is needed.  Then and only then do they come together.  Not so with a battery.  The chemicals inside a battery are always in contact.  When charging.  When the car is parked and not charging.  And when the car is being used.  At all times that chemical energy is there and has to be used.  Or contained.

G.M. attributed the June fire, which occurred at a storage facility three weeks after the car was crash-tested, to a failure to deactivate the battery. In July, it began publicizing postcrash safety protocols to emergency personnel that call for the battery to be isolated from the rest of the car via a disconnect switch and then depleted by the company.

The company says it believes the June fire was a result of crystallized coolant that leaked out of the battery’s cooling system and pooled on another portion of the pack when it was rotated as part of the crash test, a G.M. spokesman, Rob Peterson, said in an interview last week.

The N.H.T.S.A. said the testing last week that resulted in the more recent fire included damaging the battery compartment and rupturing the coolant line.

One of the byproducts of energy conversion is heat.  Gasoline-powered cars use antifreeze circulating through the engine block to remove the heat from the engine.  Then pumps it through a radiator to dump that heat into the atmosphere.  Of course, all of this happens only when the engine is running.  Apparently a car battery needs to be cooled even when the ‘engine’ isn’t running.  And the bigger we make these batteries (to match the range of gasoline engines) the more cooling they will require.  And the more critical that cooling will be to overall safety.

The advantage of gasoline is that it’s stored separately from where it is combusted to produce energy.  Whereas a battery stores chemicals together where they also produce the energy.  And the push to make batteries with greater ranges means more powerful batteries.  Potentially making these electric cars more prone to fires.  And more dangerous.

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