(CBS News) WASHINGTON - Investigators say they still don't know what caused batteries to burn in two Boeing 787 Dreamliners, and until they figure that out and how to fix the problem, none of the planes will be allowed to fly.
More than any other plane, the Dreamliner relies on lithium ion batteries to help power its advanced electrical system. They're lighter and more powerful than older battery types, but they contain a highly flammable liquid electrolyte.
Federal investigators are examining the disassembled battery from the 787 that caught fire in Boston January 7, spewing molten electrolyte.
George Blomgren worked for Eveready, a batteries and flashlights company, for 40 years. He says lithium ion batteries are bundled together for the 787, and that increases the risk.
"These fires burn at very high temperatures, so they are just very dangerous fires," he said.
The Boston fire, and the burned-out battery on a Dreamliner in Japan, is not the first time lithium ion batteries have caused problems.
In 2011, a Chevy Volt lithium ion battery was damaged in a crash test. Three weeks later, it burst into flames. Chevrolet installed a number of fixes to prevent fires.
Safety features also were added to lithium ion batteries in some cell phones and laptops after 56 million were recalled for risk of overheating and exploding.
Boeing says lithium ion batteries "best met the performance and design objectives of the 787" and "Based on everything we know at this point, we have not changed our evaluation."
Blomgren considers the safety of lithium ion batteries on planes questionable.
"From what I know about incidents, I would not fly in a Dreamliner tomorrow. I just wouldn't feel that it was appropriate or safe," Blomgren said.
Many experts believe in the promise of lithium ion batteries, including for airlines, but they just aren't sure its safety has been perfected.