Safety of Electric-Car Batteries Ignites Concern
Question: The recent Your Wheels column on battery explosions has me concerned [“How to Avoid Battery Explosions (Yes, They Really Happen),” Aug. 26)]. Is this a potential hazard on the General Motors EV1 and other electric cars, or have steps been taken to reduce the likelihood of such an explosion?
I am also curious about what safety measures are in place on the EV1 to protect against a direct short. I have seen the damage such a short does to a gasoline auto with current from only one battery. With 20 batteries, the current flow in case of a direct short would be much greater.
--P.L.
*
Answer: Battery safety is as crucial to electric vehicles as gasoline safety systems are aboard traditionally powered cars. The explosive energy in 20 gallons of gasoline is much greater than what you’ll find in an electric vehicle, but nonetheless there is a tremendous amount of energy being stored in the battery arrays of electric vehicles.
Without question, the power output of an electric vehicle--running at 200 to 300 volts--is enough to electrocute an individual or cause a fire in the case of a short circuit. And the batteries could in theory produce enough hydrogen gas for a fairly large explosion that could cause injury or destroy the vehicle.
The federal government has grown increasingly concerned about such safety questions and late last year issued proposed new rules for electric vehicles, clearly stating that electrical isolation design--that is, ensuring that wiring and components are well insulated--is essential to preventing shock hazards to occupants.
The proposed rules by the National Highway Traffic Safety Administration would also set strict limits on the amount of acid that can leak from batteries after an accident--a factor that would be critical to protecting occupants from horrific injuries after incidents such as vehicle rollovers.
Battery explosions are a serious safety hazard. A NHTSA study found that in 1993 alone, 2,280 people were injured badly enough by battery explosions to require hospitalization.
Passenger vehicles generally use 12-volt batteries, which have six 2-volt cells that contain a grid of lead plates surrounded by acid. Electricity is generated when the lead reacts with the acid and water. The process is reversed during charging. One byproduct is gaseous hydrogen, which is highly explosive.
A number of manufacturers have fought the government’s efforts to institute new safety standards, arguing that they have already minimized the dangers. Officials at General Motors Corp., which has sold or leased 600 EV1s in California and Arizona, were not available to discuss the safety record of the car.
Nearly all electric vehicles use newer-technology batteries that eliminate liquid acid and as a result minimize the production of explosive hydrogen gas.
Two types of batteries now dominate the electric vehicle field--absorbed glass mat and jell cell--said Jim Powell, a technical expert at Interstate Batteries, a major producer based in Dallas. In an AGM, the acid is held within a fibrous material, leaving just 1% in liquid form. In a jell cell, the acid is in the form of a thick paste.
In both types of batteries, hydrogen gas production is minimized during the charging cycle. But hydrogen can be produced in dangerous quantities even with AGMs and jell cells if the batteries are overcharged. With EVs, the charging occurs while the vehicles are parked, typically in a garage. So safety is all the more important in terms of preventing fire.
Even newer technologies are in the offing in nickel-metal-hydride and nickel-cadmium batteries, the dry-cell rechargeable type often used in cordless tools.
The EV1 will offer nickel-metal-hydride batteries as an option starting next month. Toyota Motor Corp.’s Prius, a hybrid gasoline-electric sedan due next year, will also employ NiMH batteries.
Eventually, Powell said, these advances over liquid-acid batteries will make their way to all passenger vehicles.
*
Ralph Vartabedian cannot answer mail personally but responds in this column to automotive questions of general interest. Please do not telephone. Write to Your Wheels, Business Section, Los Angeles Times, Times Mirror Square, Los Angeles, CA 90053. E-mail: ralph.vartabedian @latimes.com.
