Say an electric car is in a very severe car accident. Would this create a massive burst of electricity, electrocuting the passengers?
If you toss an alkaline battery to the floor, does it go SHAZAMMM! on you? No, it doesn’t. The old car batteries, the ones with sulfuric acid inside, would have caused a puddle of sulfuric acid but wouldn’t have caused a localized bolt of lightning - batteries with no liquids break into solid chunks but, again, do not release their whole electrical energy in a burst when hit.
The battery has over-current protection (i.e. fuses or circuit breakers) which should trip in the case of a short to ground. Further, even if they didn’t, the current is being shunted to ground (the chassis of the car) which shouldn’t pass through the occupants. put it this way, a conventional car with a gas engine has multiple coils generating 20,000-60,000 volts up front firing the spark plugs, and nobody gets zapped.
if your reason for asking this has to do with the Chevy Volt, that’s a completely different situation.
Batteries are electrochemical cells; that is, they produce a potential difference by virtue of the galvanic differential between the anode and cathode (negative and positive sides). Increasing the rate of reaction will increase the current delivered and for some chemicals in direct contact can result in combustion, but they won’t create a massive burst of electrostatic charge that the o.p. is imaginging. Lithium ion batteries that are typically used in automotive electric motor applications are already distributed cell arrangements that won’t react signficiantly faster even if ruptured, though they can combust in the presence of water.
A very dense capacitor bank might produce a large release of electrical charge, but batteries do not accumulate charge in that fashion, which would actually be detrimental to the function of a battery. The power throughput of a battery is roughly linear (slightly decreasing) through at least the high end of function, while a capacitor is by definition exponentially decreasing. In other words, capacitors are designed to accumulate and then deliver a large amout of electric charge very quickly (high instantaneous current), while batteries are designed to produce current in a slow, controlled fashion.
Stranger
*Nissan inadvertently gained some valuable insight into the durability of its electric car, the Leaf, when about two dozen of them were destroyed in the tsunami that ravaged Japan in March.
None of the cars caught fire, and their batteries remained fully intact, shielded by an airtight steel exoskeleton and two other layers of protection that surround the 660-pound packs.
*
If the battery short circuits, won’t it catch fire like laptop batteries? It might also release nasty chemicals like HF.
an external short circuit should kick in the battery’s overcurrent protection. I don’t know if the individual cells have their own safeguards.
however, the infamous laptop/mobile device battery fires were from internal short circuits, which no cell is protected against.
As I read all the stories of concern over battery packs after a collision, I find myself wondering if we could ever find approval for current technology. If we were just introducing tanks of flammable liquids in vehicles, would we approve that technology?
The main issue I’d heard of relating to electric cars in accidents is that in normal cars the columns (i.e. the struts on the outside between the front and rear passenger compartments) are just structural in gasoline cars, but some electric cars have high-voltage power cables running through them. So in a bad accident, the EMTs might be thinking they can use the jaws of life to cut through the columns to access injured passengers with no problem, when they are cutting through possibly still live cabling.
Yes, it’s quite likely that a battery will be speared by a piece of metal in a crash, short circuiting the electrodes. This will probably lead to fire/explosions of a bigger scale than seen with laptop batteries.
How likely is “quite likely”
Many hybrids use nickel–metal hydride batteries thus they may have a lower risk vector but even with the Lithium-Ion based cars the risk is probably less then “quite likely”.
Many of the laptop/cellphone LiPo fires were caused by improper or uneven cell charging vs physical damage to the cell.
The batteries in hybrids and electric cars tend to be inside metal boxes inside the same cage that protects humans, I can not find any statistics on how often it is for human occupants to be speared by metal outside of the cars controls.
According to these cites the risk of fire is real, but not any greater and probably lower than gas powered cars.
Obviously, as shown by the NTSB having a fire 3 weeks after crash testing a volt the larger concern is with those who tow, house and work on crashed cars.
I’m confused, do you think that the automakers didn’t think of that?
The body of cars acts like a faraday cage, if your car got hit by lightning you would still be fine.
A car body is not a good Faraday cage (as demonstrated by the ability to make and receive calls on your cellphone within) and a Faraday cage does not protect the occupants against electrical transients such as a lightning strike.
Stranger