Hybrid engines: Are they safe?

• Author: Johnson, Walter L.
• Position: LETTERS - Letter to the editor

It is great that the Pentagon is taking a serious look at the need for better fuel economy (National Defense, April 2007, page 30). However, I wonder if anyone has considered the increased hazard that electric hybrid vehicles have if the battery compartment is hit.

I bought a Toyota Prius, which has a main 274-volt nickel metal hydride (NiMH) battery pack consisting of 38 low voltage 7.2 V modules connected in series. It cannot be disposed of in a landfill, and must be recycled. It is generally safe in an accident because the electrolyte is an alkaline of potassium and sodium but is absorbed in battery cell plates and won't leak because it exists as a gel and is dual protected. The main risk is electrocution. If the electrolyte does come in contact with people it is caustic and damages skin. In a civilian or domestic National Guard situation, this vehicle is completely safe, but testing would need to take place for military use to determine occupant risk from intentional explosions, such as exist in war.

A truck would probably need higher voltage. If it needs a lithium ion battery to reduce weight while increasing power, the explosive and burn injury risk would be far greater in combat. I would...